ZDZ Lab | Publications

Evidence for Improved DNA Repair in the Long-Lived Bowhead Whale.
Firsanov D, Zacher M, Tian X, Sformo TL, Zhao Y, Tombline G, Lu JY, Zheng Z, Perelli L, Gurreri E, Zhang L, Guo J, Korotkov A, Volobaev V, Biashad SA, Zhang Z, Heid J, Maslov AY, Sun S, Wu Z, Gigas J, Hillpot EC, Martinez JC, Lee M, Williams A, Gilman A, Hamilton N, Strelkova E, Haseljic E, Patel A, Straight ME, Miller N, Ablaeva J, Tam LM, Couderc C, Hoopmann MR, Moritz RL, Fujii S, Pelletier A, Hayman DJ, Liu H, Cai Y, Leung AKL, Zhang Z, Nelson CB, Abegglen LM, Schiffman JD, Gladyshev VN, Maley CC, Modesti M, Genovese G, Simons MJP, Vijg J, Seluanov A, Gorbunova V (2025) Nature 648(8094):717-725. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: At more than 200 years, the maximum lifespan of the bowhead whale exceeds that of all other mammals. The bowhead is also the second-largest animal on Earth1, reaching over 80,000 kg. Despite its very large number of cells and long lifespan, the bowhead is not highly cancer-prone, an incongruity termed Peto's paradox2. Here, to understand the mechanisms that underlie the cancer resistance of the bowhead whale, we examined the number of oncogenic hits required for malignant transformation of whale primary fibroblasts. Unexpectedly, bowhead whale fibroblasts required fewer oncogenic hits to undergo malignant transformation than human fibroblasts. However, bowhead whale cells exhibited enhanced DNA double-strand break repair capacity and fidelity, and lower mutation rates than cells of other mammals. We found the cold-inducible RNA-binding protein CIRBP to be highly expressed in bowhead fibroblasts and tissues. Bowhead whale CIRBP enhanced both non-homologous end joining and homologous recombination repair in human cells, reduced micronuclei formation, promoted DNA end protection, and stimulated end joining in vitro. CIRBP overexpression in Drosophila extended lifespan and improved resistance to irradiation. These findings provide evidence supporting the hypothesis that, rather than relying on additional tumour suppressor genes to prevent oncogenesis3-5, the bowhead whale maintains genome integrity through enhanced DNA repair. This strategy, which does not eliminate damaged cells but faithfully repairs them, may be contributing to the exceptional longevity and low cancer incidence in the bowhead whale.

Identification of Functional Rare Coding Variants in IGF-1 Gene in Humans with Exceptional Longevity.
Ali A, Zhang ZD, Gao T, Aleksic S, Gavathiotis E, Barzilai N, Milman S (2025) Sci Rep 15(1):10199. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: Diminished signaling via insulin/insulin-like growth factor-1 (IGF-1) axis is associated with longevity in different model organisms. IGF-1 gene is highly conserved across species, with only few evolutionary changes identified in it. Despite its potential role in regulating lifespan, no coding variants in IGF-1 have been reported in human longevity cohorts to date. This study investigated the whole exome sequencing data from 2,108 individuals in a cohort of Ashkenazi Jewish centenarians, their offspring, and controls without familial longevity to identify functional IGF-1 coding variants. We identified two likely functional coding variants IGF-1:p.Ile91Leu and IGF-1:p.Ala118Thr in our longevity cohort. Notably, a centenarian specific novel variant IGF-1:p.Ile91Leu was located at the binding interface of IGF-1-IGF-1R, whereas IGF-1:p.Ala118Thr was significantly associated with lower circulating levels of IGF-1. We performed extended all-atom molecular dynamics simulations to evaluate the impact of Ile91Leu on stability, binding dynamics and energetics of IGF-1 bound to IGF-1R. The IGF-1:p.Ile91Leu formed less stable interactions with IGF-1R's critical binding pocket residues and demonstrated lower binding affinity at the extracellular binding site compared to wild-type IGF-1. Our findings suggest that IGF-1:p.Ile91Leu and IGF-1:p.Ala118Thr variants attenuate IGF-1R activity by impairing IGF-1 binding and diminishing the circulatory levels of IGF-1, respectively. Consequently, diminished IGF-1 signaling resulting from these variants may contribute to exceptional longevity in humans.

Genetic Variants Associated with Age-Related Episodic Memory Decline Implicate Distinct Memory Pathologies.
Ali A, Milman S, Weiss EF, Gao T, Napolioni V, Barzilai N, Zhang ZD, Lin JR (2025) Alzheimers Dement 21(1):e14379. JOURNAL PUBMED REPRINT AGING · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: BACKGROUND: Approximately 40% of people aged ≥ 65 experience memory loss, particularly in episodic memory. Identifying the genetic basis of episodic memory decline is crucial for uncovering its underlying causes. METHODS: We investigated common and rare genetic variants associated with episodic memory decline in 742 (632 for rare variants) Ashkenazi Jewish individuals (mean age 75) from the LonGenity study. All-atom molecular dynamics simulations were performed to uncover mechanistic insights underlying rare variants associated with episodic memory decline. RESULTS: In addition to the common polygenic risk of Alzheimer's disease, we identified and replicated rare variant associations in ITSN1 and CRHR2. Structural analyses revealed distinct memory pathologies mediated by interfacial rare coding variants such as impaired receptor activation of corticotropin releasing hormone and dysregulated L-serine synthesis. DISCUSSION: Our study uncovers novel risk loci for episodic memory decline. The identified underlying mechanisms point toward heterogenous memory pathologies mediated by rare coding variants. HIGHLIGHTS: We demonstrated the contribution of the common polygenic risk of Alzheimer's disease to episodic memory decline. We discovered and replicated two risk genes associated with episodic memory decline implicated by rare variants, were discovered and replicated. We demonstrated molecular mechanisms and potential novel memory pathologies underlying interfacial rare coding variants. Molecular dynamics simulations were performed to understand the downstream effects of risk rare coding variants.

Polygenic Prediction of Human Longevity on the Supposition of Pervasive Pleiotropy.
Jabalameli MR, Lin JR, Zhang Q, Wang Z, Mitra J, Nguyen N, Gao T, Khusidman M, Sathyan S, Atzmon G, Milman S, Vijg J, Barzilai N, Zhang ZD (2024) Sci Rep 14(1):19981. JOURNAL PUBMED REPRINT AGING · GENETIC VARIATION

ABSTRACT: The highly polygenic nature of human longevity renders pleiotropy an indispensable feature of its genetic architecture. Leveraging the genetic correlation between aging-related traits (ARTs), we aimed to model the additive variance in lifespan as a function of the cumulative liability from pleiotropic segregating variants. We tracked allele frequency changes as a function of viability across different age bins and prioritized 34 variants with an immediate implication on lipid metabolism, body mass index (BMI), and cognitive performance, among other traits, revealed by PheWAS analysis in the UK Biobank. Given the highly complex and non-linear interactions between the genetic determinants of longevity, we reasoned that a composite polygenic score would approximate a substantial portion of the variance in lifespan and developed the integrated longevity genetic scores (iLGSs) for distinguishing exceptional survival. We showed that coefficients derived from our ensemble model could potentially reveal an interesting pattern of genomic pleiotropy specific to lifespan. We assessed the predictive performance of our model for distinguishing the enrichment of exceptional longevity among long-lived individuals in two replication cohorts (the Scripps Wellderly cohort and the Medical Genome Reference Bank (MRGB)) and showed that the median lifespan in the highest decile of our composite prognostic index is up to 4.8 years longer. Finally, using the proteomic correlates of iLGS, we identified protein markers associated with exceptional longevity irrespective of chronological age and prioritized drugs with repurposing potentials for gerotherapeutics. Together, our approach demonstrates a promising framework for polygenic modeling of additive liability conferred by ARTs in defining exceptional longevity and assisting the identification of individuals at a higher risk of mortality for targeted lifestyle modifications earlier in life. Furthermore, the proteomic signature associated with iLGS highlights the functional pathway upstream of the PI3K-Akt that can be effectively targeted to slow down aging and extend lifespan.

Frailty Resilience Score: A Novel Measure of Frailty Resilience Associated with Protection from Frailty and Survival.
Milman S, Lerman B, Ayers E, Zhang Z, Sathyan S, Levine M, Ye K, Gao T, Higgins-Chen A, Barzilai N, Verghese J (2023) J Gerontol A Biol Sci Med Sci 78(10):1771-1777. JOURNAL PUBMED REPRINT AGING

ABSTRACT: Frailty is characterized by increased vulnerability to disability and high risk for mortality in older adults. Identification of factors that contribute to frailty resilience is an important step in the development of effective therapies that protect against frailty. First, a reliable quantification of frailty resilience is needed. We developed a novel measure of frailty resilience, the Frailty Resilience Score (FRS), that integrates frailty genetic risk, age, and sex. Application of FRS to the LonGenity cohort (n = 467, mean age 74.4) demonstrated its validity compared to phenotypic frailty and its utility as a reliable predictor of overall survival. In a multivariable-adjusted analysis, 1-standard deviation increase in FRS predicted a 38% reduction in the hazard of mortality, independent of baseline frailty (p < .001). Additionally, FRS was used to identify a proteomic profile of frailty resilience. FRS was shown to be a reliable measure of frailty resilience that can be applied to biological studies of resilience.

◸ NEWS AND VIEWS
Unravelling Genetic Components of Longevity.
Jabalameli MR, Zhang ZD (2022) Nat Aging 2(1):5-6. JOURNAL PUBMED REPRINT AGING · DISEASE STUDY · GENETIC VARIATION · REVIEW / PERSPECTIVE

ABSTRACT: Many aging-related traits share a common genetic component. How to disentangle it from the trait-specific effects has remained largely unexplored. A new study in Nature Aging uses an analysis framework for isolating the shared genetic component in genome-wide association studies of aging-related traits and identifies genomic loci that contribute to aging.

Genomic Expansion of Aldh1a1 Protects Beavers Against High Metabolic Aldehydes from Lipid Oxidation.
Zhang Q, Tombline G, Ablaeva J, Zhang L, Zhou X, Smith Z, Zhao Y, Xiaoli AM, Wang Z, Lin JR, Jabalameli MR, Mitra J, Nguyen N, Vijg J, Seluanov A, Gladyshev VN, Gorbunova V, Zhang ZD (2021) Cell Rep 37(6):109965. JOURNAL PUBMED REPRINT AGING · COMPARATIVE GENOMICS · EVOLUTIONARY GENOMICS

ABSTRACT: The North American beaver is an exceptionally long-lived and cancer-resistant rodent species. Here, we report the evolutionary changes in its gene coding sequences, copy numbers, and expression. We identify changes that likely increase its ability to detoxify aldehydes, enhance tumor suppression and DNA repair, and alter lipid metabolism, potentially contributing to its longevity and cancer resistance. Hpgd, a tumor suppressor gene, is uniquely duplicated in beavers among rodents, and several genes associated with tumor suppression and longevity are under positive selection in beavers. Lipid metabolism genes show positive selection signals, changes in copy numbers, or altered gene expression in beavers. Aldh1a1, encoding an enzyme for aldehydes detoxification, is particularly notable due to its massive expansion in beavers, which enhances their cellular resistance to ethanol and capacity to metabolize diverse aldehyde substrates from lipid oxidation and their woody diet. We hypothesize that the amplification of Aldh1a1 may contribute to the longevity of beavers.

Rare Genetic Coding Variants Associated with Human Longevity and Protection Against Age-Related Diseases.
Lin JR, Sin-Chan P, Napolioni V, Torres GG, Mitra J, Zhang Q, Jabalameli MR, Wang Z, Nguyen N, Gao T, Regeneron Genetics Center, Laudes M, Görg S, Franke A, Nebel A, Greicius MD, Atzmon G, Ye K, Gorbunova V, Ladiges WC, Shuldiner AR, Niedernhofer LJ, Robbins PD, Milman S, Suh Y, Vijg J, Barzilai N, Zhang ZD (2021) Nat Aging 1(9):783-794. JOURNAL PUBMED REPRINT WEBSITE AGING · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: Extreme longevity in humans has a strong genetic component, but whether this involves genetic variation in the same longevity pathways as found in model organisms is unclear. Using whole-exome sequences of a large cohort of Ashkenazi Jewish centenarians to examine enrichment for rare coding variants, we found most longevity-associated rare coding variants converge upon conserved insulin/insulin-like growth factor 1 signaling and AMP-activating protein kinase signaling pathways. Centenarians have a number of pathogenic rare coding variants similar to control individuals, suggesting that rare variants detected in the conserved longevity pathways are protective against age-related pathology. Indeed, we detected a pro-longevity effect of rare coding variants in the Wnt signaling pathway on individuals harboring the known common risk allele APOE4. The genetic component of extreme human longevity constitutes, at least in part, rare coding variants in pathways that protect against aging, including those that control longevity in model organisms.

Genetics of Extreme Human Longevity to Guide Drug Discovery for Healthy Ageing.
Zhang ZD, Milman S, Lin JR, Wierbowski S, Yu H, Barzilai N, Gorbunova V, Ladiges WC, Niedernhofer LJ, Suh Y, Robbins PD, Vijg J (2020) Nat Metab 2(8):663-672. JOURNAL PUBMED REPRINT AGING · DISEASE STUDY · GENETIC VARIATION · REVIEW / PERSPECTIVE

ABSTRACT: Ageing is the greatest risk factor for most common chronic human diseases, and it therefore is a logical target for developing interventions to prevent, mitigate or reverse multiple age-related morbidities. Over the past two decades, genetic and pharmacologic interventions targeting conserved pathways of growth and metabolism have consistently led to substantial extension of the lifespan and healthspan in model organisms as diverse as nematodes, flies and mice. Recent genetic analysis of long-lived individuals is revealing common and rare variants enriched in these same conserved pathways that significantly correlate with longevity. In this Perspective, we summarize recent insights into the genetics of extreme human longevity and propose the use of this rare phenotype to identify genetic variants as molecular targets for gaining insight into the physiology of healthy ageing and the development of new therapies to extend the human healthspan.

Beaver and Naked Mole Rat Genomes Reveal Common Paths to Longevity.
Zhou X, Dou Q, Fan G, Zhang Q, Sanderford M, Kaya A, Johnson J, Karlsson EK, Tian X, Mikhalchenko A, Kumar S, Seluanov A, Zhang ZD, Gorbunova V, Liu X, Gladyshev VN (2020) Cell Rep 32(4):107949. JOURNAL PUBMED REPRINT AGING · COMPARATIVE GENOMICS · EVOLUTIONARY GENOMICS

ABSTRACT: Long-lived rodents have become an attractive model for the studies on aging. To understand evolutionary paths to long life, we prepare chromosome-level genome assemblies of the two longest-lived rodents, Canadian beaver (Castor canadensis) and naked mole rat (NMR, Heterocephalus glaber), which were scaffolded with in vitro proximity ligation and chromosome conformation capture data and complemented with long-read sequencing. Our comparative genomic analyses reveal that amino acid substitutions at "disease-causing" sites are widespread in the rodent genomes and that identical substitutions in long-lived rodents are associated with common adaptive phenotypes, e.g., enhanced resistance to DNA damage and cellular stress. By employing a newly developed substitution model and likelihood ratio test, we find that energy and fatty acid metabolism pathways are enriched for signals of positive selection in both long-lived rodents. Thus, the high-quality genome resource of long-lived rodents can assist in the discovery of genetic factors that control longevity and adaptive evolution.

Inducible Aging in Hydra Oligactis Implicates Sexual Reproduction, Loss of Stem Cells, and Genome Maintenance as Major Pathways.
Sun S, White RR, Fischer KE, Zhang Z, Austad SN, Vijg J (2020) Geroscience 42(4):1119-1132. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: Freshwater polyps of the genus Hydra do not age. However, temperature stress induces aging and a shift from reproduction by asexual budding to sexual gamete production in a cold-sensitive (CS) strain of H. oligactis. We sequenced the transcriptome of a male CS strain before and after this life history shift and compared changes in gene expression relative to those seen in a cold-resistant (CR) strain that does not undergo a life history shift in response to altered temperature. We found that the switch from non-aging asexual reproduction to aging and sexual reproduction involves upregulation of genes not only involved in gametogenesis but also genes involved in cellular senescence, apoptosis, and DNA repair accompanied by a downregulation of genes involved in stem cell maintenance. These results suggest that aging is a byproduct of sexual reproduction-associated cellular reprogramming and underscore the power of these H. oligactis strains to identify intrinsic mechanisms of aging.

SIRT6 Is Responsible for More Efficient DNA Double-Strand Break Repair in Long-Lived Species.
Tian X, Firsanov D, Zhang Z, Cheng Y, Luo L, Tombline G, Tan R, Simon M, Henderson S, Steffan J, Goldfarb A, Tam J, Zheng K, Cornwell A, Johnson A, Yang JN, Mao Z, Manta B, Dang W, Zhang Z, Vijg J, Wolfe A, Moody K, Kennedy BK, Bohmann D, Gladyshev VN, Seluanov A, Gorbunova V (2019) Cell 177(3):622-638.e22. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: DNA repair has been hypothesized to be a longevity determinant, but the evidence for it is based largely on accelerated aging phenotypes of DNA repair mutants. Here, using a panel of 18 rodent species with diverse lifespans, we show that more robust DNA double-strand break (DSB) repair, but not nucleotide excision repair (NER), coevolves with longevity. Evolution of NER, unlike DSB, is shaped primarily by sunlight exposure. We further show that the capacity of the SIRT6 protein to promote DSB repair accounts for a major part of the variation in DSB repair efficacy between short- and long-lived species. We dissected the molecular differences between a weak (mouse) and a strong (beaver) SIRT6 protein and identified five amino acid residues that are fully responsible for their differential activities. Our findings demonstrate that DSB repair and SIRT6 have been optimized during the evolution of longevity, which provides new targets for anti-aging interventions.

Translation Fidelity Coevolves with Longevity.
Ke Z, Mallik P, Johnson AB, Luna F, Nevo E, Zhang ZD, Gladyshev VN, Seluanov A, Gorbunova V (2017) Aging Cell 16(5):988-993. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY

ABSTRACT: Whether errors in protein synthesis play a role in aging has been a subject of intense debate. It has been suggested that rare mistakes in protein synthesis in young organisms may result in errors in the protein synthesis machinery, eventually leading to an increasing cascade of errors as organisms age. Studies that followed generally failed to identify a dramatic increase in translation errors with aging. However, whether translation fidelity plays a role in aging remained an open question. To address this issue, we examined the relationship between translation fidelity and maximum lifespan across 17 rodent species with diverse lifespans. To measure translation fidelity, we utilized sensitive luciferase-based reporter constructs with mutations in an amino acid residue critical to luciferase activity, wherein misincorporation of amino acids at this mutated codon re-activated the luciferase. The frequency of amino acid misincorporation at the first and second codon positions showed strong negative correlation with maximum lifespan. This correlation remained significant after phylogenetic correction, indicating that translation fidelity coevolves with longevity. These results give new life to the role of protein synthesis errors in aging: Although the error rate may not significantly change with age, the basal rate of translation errors is important in defining lifespan across mammals.

Cell Culture-Based Profiling Across Mammals Reveals DNA Repair and Metabolism as Determinants of Species Longevity.
Ma S, Upneja A, Galecki A, Tsai YM, Burant CF, Raskind S, Zhang Q, Zhang ZD, Seluanov A, Gorbunova V, Clish CB, Miller RA, Gladyshev VN (2016) Elife 5:e19130. JOURNAL PUBMED REPRINT AGING · COMPARATIVE GENOMICS

ABSTRACT: Mammalian lifespan differs by >100 fold, but the mechanisms associated with such longevity differences are not understood. Here, we conducted a study on primary skin fibroblasts isolated from 16 species of mammals and maintained under identical cell culture conditions. We developed a pipeline for obtaining species-specific ortholog sequences, profiled gene expression by RNA-seq and small molecules by metabolite profiling, and identified genes and metabolites correlating with species longevity. Cells from longer lived species up-regulated genes involved in DNA repair and glucose metabolism, down-regulated proteolysis and protein transport, and showed high levels of amino acids but low levels of lysophosphatidylcholine and lysophosphatidylethanolamine. The amino acid patterns were recapitulated by further analyses of primate and bird fibroblasts. The study suggests that fibroblast profiling captures differences in longevity across mammals at the level of global gene expression and metabolite levels and reveals pathways that define these differences.

Systems-Level Analysis of Human Aging Genes Shed New Light on Mechanisms of Aging.
Zhang Q, Nogales-Cadenas R, Lin JR, Zhang W, Cai Y, Vijg J, Zhang ZD (2016) Hum Mol Genet 25(14):2934-2947. JOURNAL PUBMED REPRINT AGING · SYSTEMS BIOLOGY

ABSTRACT: Although studies over the last decades have firmly connected a number of genes and molecular pathways to aging, the aging process as a whole still remains poorly understood. To gain novel insights into the mechanisms underlying aging, instead of considering aging genes individually, we studied their characteristics at the systems level in the context of biological networks. We calculated a comprehensive set of network characteristics for human aging-related genes from the GenAge database. By comparing them with other functional groups of genes, we identified a robust group of aging-specific network characteristics. To find the structural basis and the molecular mechanisms underlying this aging-related network specificity, we also analyzed protein domain interactions and gene expression patterns across different tissues. Our study revealed that aging genes not only tend to be network hubs, playing important roles in communication among different functional modules or pathways, but also are more likely to physically interact and be co-expressed with essential genes. The high expression of aging genes across a large number of tissue types also points to a high level of connectivity among aging genes. Unexpectedly, contrary to the depletion of interactions among hub genes in biological networks, we observed close interactions among aging hubs, which renders the aging subnetworks vulnerable to random attacks and thus may contribute to the aging process. Comparison across species reveals the evolution process of the aging subnetwork. As the organisms become more complex, the complexity of its aging mechanisms increases and their aging hub genes are more functionally connected.

DNA Repair in Species with Extreme Lifespan Differences.
MacRae SL, Croken MM, Calder RB, Aliper A, Milholland B, White RR, Zhavoronkov A, Gladyshev VN, Seluanov A, Gorbunova V, Zhang ZD, Vijg J (2015) Aging (Albany NY) 7(12):1171-84. JOURNAL PUBMED REPRINT AGING · COMPARATIVE GENOMICS · EVOLUTIONARY GENOMICS

ABSTRACT: Differences in DNA repair capacity have been hypothesized to underlie the great range of maximum lifespans among mammals. However, measurements of individual DNA repair activities in cells and animals have not substantiated such a relationship because utilization of repair pathways among animals--depending on habitats, anatomical characteristics, and life styles--varies greatly between mammalian species. Recent advances in high-throughput genomics, in combination with increased knowledge of the genetic pathways involved in genome maintenance, now enable a comprehensive comparison of DNA repair transcriptomes in animal species with extreme lifespan differences. Here we compare transcriptomes of liver, an organ with high oxidative metabolism and abundant spontaneous DNA damage, from humans, naked mole rats, and mice, with maximum lifespans of ~120, 30, and 3 years, respectively, with a focus on genes involved in DNA repair. The results show that the longer-lived species, human and naked mole rat, share higher expression of DNA repair genes, including core genes in several DNA repair pathways. A more systematic approach of signaling pathway analysis indicates statistically significant upregulation of several DNA repair signaling pathways in human and naked mole rat compared with mouse. The results of this present work indicate, for the first time, that DNA repair is upregulated in a major metabolic organ in long-lived humans and naked mole rats compared with short-lived mice. These results strongly suggest that DNA repair can be considered a genuine longevity assurance system.

Comparative Analysis of Genome Maintenance Genes in Naked Mole Rat, Mouse, and Human.
MacRae SL, Zhang Q, Lemetre C, Seim I, Calder RB, Hoeijmakers J, Suh Y, Gladyshev VN, Seluanov A, Gorbunova V, Vijg J, Zhang ZD (2015) Aging Cell 14(2):288-91. JOURNAL PUBMED REPRINT AGING · COMPARATIVE GENOMICS · EVOLUTIONARY GENOMICS

ABSTRACT: Genome maintenance (GM) is an essential defense system against aging and cancer, as both are characterized by increased genome instability. Here, we compared the copy number variation and mutation rate of 518 GM-associated genes in the naked mole rat (NMR), mouse, and human genomes. GM genes appeared to be strongly conserved, with copy number variation in only four genes. Interestingly, we found NMR to have a higher copy number of CEBPG, a regulator of DNA repair, and TINF2, a protector of telomere integrity. NMR, as well as human, was also found to have a lower rate of germline nucleotide substitution than the mouse. Together, the data suggest that the long-lived NMR, as well as human, has more robust GM than mouse and identifies new targets for the analysis of the exceptional longevity of the NMR.

Comparative Genetics of Longevity and Cancer: Insights from Long-Lived Rodents.
Gorbunova V, Seluanov A, Zhang Z, Gladyshev VN, Vijg J (2014) Nat Rev Genet 15(8):531-40. JOURNAL PUBMED REPRINT AGING · REVIEW / PERSPECTIVE

ABSTRACT: Mammals have evolved a remarkable diversity of ageing rates. Within the single order of Rodentia, maximum lifespans range from 4 years in mice to 32 years in naked mole rats. Cancer rates also differ substantially between cancer-prone mice and almost cancer-proof naked mole rats and blind mole rats. Recent progress in rodent comparative biology, together with the emergence of whole-genome sequence information, has opened opportunities for the discovery of genetic factors that control longevity and cancer susceptibility.

Direct Probabilistic Quantification of Mosaic Loss of Chromosome Y from Sequencing Data
Lin J-R, Chang Y-C, Maslov AY, Song Y, Gao T, Shan J, Bennett D, Milman S, Barzilai N, Vijg J, Montagna C, Zhang ZD (2026) bioRxiv 2026.06.26.734767. JOURNAL ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: Loss of chromosome Y (LOY) is the most common aneuploidy in aging men and is increasingly recognized as a marker of aging and genomic instability. Because LOY occurs in mosaic form, its degree reflects the fraction of cells lacking the Y chromosome. Existing SNP-array- and sequencing-based methods rely largely on single genomic features and indirect transformations to estimate this fraction. We developed BaySeq-Y, a Bayesian method that directly estimates LOY mosaicism from sequencing data using VCF files with read depth (DP) and allelic depth (AD). Within a rigorous Bayesian framework, BaySeq-Y integrates complementary LOY-associated genomic features, including decreased read depth and allelic imbalance, and can additionally leverage haplotype phasing to improve precision. In simulations and fluorescence in situ hybridization validation (FISH), BaySeq-Y provided accurate estimates and outperformed existing methods. Applications to ROSMAP and GTEx supported its biological relevance through transcriptomic validation, demonstrating its utility for quantifying LOY across diverse sequencing datasets.

Bayesian Estimation of Mosaic Loss of Chromosome Y from Bulk RNA Sequencing Data
Lin J-R, Zhang ZD (2026) bioRxiv 2026.05.20.726153. JOURNAL ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: Mosaic loss of chromosome Y (LOY) is a common age-associated somatic alteration in men and is typically measured from DNA-based assays. Many cohorts, however, contain bulk RNA-seq data without matched DNA-based LOY measurements. We developed a Bayesian framework to estimate the fraction of cells with LOY from male bulk RNA-seq by modeling reduced Y-linked gene expression relative to expected expression after adjustment for age, expression covariates, and autosomal/X-linked control genes. In 377 male GTEx samples, individual Y-linked genes showed negative correlations with separately obtained DNA-based LOY measurements, supporting a shared Y-expression depletion signal. The primary fast empirical Bayes estimator achieved a Pearson correlation of 0.678 with measured LOY, a mean absolute error of 1.79%, a root mean squared error of 3.72%, and 95.2% empirical coverage of measured LOY. Performance was strongest for identifying large LOY events, with an AUC of 0.964 for measured LOY greater than 20%, while fine ranking among low-LOY samples remained uncertain. A mixture/PCA hierarchical Bayesian sensitivity model provided similar validation performance and interpretable posterior quantities but did not improve point estimation. Leave-one-Y-gene-out and prior-sensitivity analyses showed that the signal was distributed across multiple Y-linked transcripts and that prior shrinkage affected calibration. In an external whole-blood RNA-seq dataset without measured LOY, estimated LOY showed a modest age-related increase, but ex vivo immune stimulation shifted RNA-derived LOY estimates and reduced multiple Y-linked transcripts, indicating transcriptional confounding. These results show that bulk RNA-seq contains usable information about LOY, especially for larger events, but RNA-derived LOY should be interpreted as a probabilistic transcriptome-based estimate rather than a direct substitute for DNA-based mosaicism measurement.

Rare Coding Variants as Risk Modifiers of the 22q11.2 Deletion Implicate Postnatal Cortical Development in Syndromic Schizophrenia.
Lin JR, Zhao Y, Jabalameli MR, Nguyen N, Mitra J, International 22q11.DS Brain and Behavior Consortium, Swillen A, Vorstman JAS, Chow EWC, van den Bree M, Emanuel BS, Vermeesch JR, Owen MJ, Williams NM, Bassett AS, McDonald-McGinn DM, Gur RE, Bearden CE, Morrow BE, Lachman HM, Zhang ZD (2023) Mol Psychiatry 28(5):2071-2080. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: 22q11.2 deletion is one of the strongest known genetic risk factors for schizophrenia. Recent whole-genome sequencing of schizophrenia cases and controls with this deletion provided an unprecedented opportunity to identify risk modifying genetic variants and investigate their contribution to the pathogenesis of schizophrenia in 22q11.2 deletion syndrome. Here, we apply a novel analytic framework that integrates gene network and phenotype data to investigate the aggregate effects of rare coding variants and identified modifier genes in this etiologically homogenous cohort (223 schizophrenia cases and 233 controls of European descent). Our analyses revealed significant additive genetic components of rare nonsynonymous variants in 110 modifier genes (adjusted P = 9.4E-04) that overall accounted for 4.6% of the variance in schizophrenia status in this cohort, of which 4.0% was independent of the common polygenic risk for schizophrenia. The modifier genes affected by rare coding variants were enriched with genes involved in synaptic function and developmental disorders. Spatiotemporal transcriptomic analyses identified an enrichment of coexpression between modifier and 22q11.2 genes in cortical brain regions from late infancy to young adulthood. Corresponding gene coexpression modules are enriched with brain-specific protein-protein interactions of SLC25A1, COMT, and PI4KA in the 22q11.2 deletion region. Overall, our study highlights the contribution of rare coding variants to the SCZ risk. They not only complement common variants in disease genetics but also pinpoint brain regions and developmental stages critical to the etiology of syndromic schizophrenia.

Protocol for Gene Annotation, Prediction, and Validation of Genomic Gene Expansion.
Zhang Q, Zhang ZD (2022) STAR Protoc 3(4):101692. JOURNAL PUBMED REPRINT ANALYTICAL METHOD · COMPARATIVE GENOMICS · EVOLUTIONARY GENOMICS · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: Although gene expansion plays an important role in evolution, its identification remains a challenge due to potential errors in genome assembly and annotation. Here, we describe a detailed step-by-step protocol for gene annotation, prediction of genomic gene expansion, and its computational and experimental validation. Finally, we also detail steps to discover functionality of each copy of replicated genes. For complete details on the use and execution of this protocol, please refer to Zhang et al. (2021).

Deep Post-Gwas Analysis Identifies Potential Risk Genes and Risk Variants for Alzheimer's Disease, Providing New Insights into Its Disease Mechanisms.
Wang Z, Zhang Q, Lin JR, Jabalameli MR, Mitra J, Nguyen N, Zhang ZD (2021) Sci Rep 11(1):20511. JOURNAL PUBMED REPRINT ANALYTICAL METHOD · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: Alzheimer's disease (AD) is a genetically complex, multifactorial neurodegenerative disease. It affects more than 45 million people worldwide and currently remains untreatable. Although genome-wide association studies (GWAS) have identified many AD-associated common variants, only about 25 genes are currently known to affect the risk of developing AD, despite its highly polygenic nature. Moreover, the risk variants underlying GWAS AD-association signals remain unknown. Here, we describe a deep post-GWAS analysis of AD-associated variants, using an integrated computational framework for predicting both disease genes and their risk variants. We identified 342 putative AD risk genes in 203 risk regions spanning 502 AD-associated common variants. 246 AD risk genes have not been identified as AD risk genes by previous GWAS collected in GWAS catalogs, and 115 of 342 AD risk genes are outside the risk regions, likely under the regulation of transcriptional regulatory elements contained therein. Even more significantly, for 109 AD risk genes, we predicted 150 risk variants, of both coding and regulatory (in promoters or enhancers) types, and 85 (57%) of them are supported by functional annotation. In-depth functional analyses showed that AD risk genes were overrepresented in AD-related pathways or GO terms-e.g., the complement and coagulation cascade and phosphorylation and activation of immune response-and their expression was relatively enriched in microglia, endothelia, and pericytes of the human brain. We found nine AD risk genes-e.g., IL1RAP, PMAIP1, LAMTOR4-as predictors for the prognosis of AD survival and genes such as ARL6IP5 with altered network connectivity between AD patients and normal individuals involved in AD progression. Our findings open new strategies for developing therapeutics targeting AD risk genes or risk variants to influence AD pathogenesis.

PGA: Post-Gwas Analysis for Disease Gene Identification.
Lin JR, Jaroslawicz D, Cai Y, Zhang Q, Wang Z, Zhang ZD (2018) Bioinformatics 34(10):1786-1788. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: SUMMARY: Although the genome-wide association study (GWAS) is a powerful method to identify disease-associated variants, it does not directly address the biological mechanisms underlying such genetic association signals. Here, we present PGA, a Perl- and Java-based program for post-GWAS analysis that predicts likely disease genes given a list of GWAS-reported variants. Designed with a command line interface, PGA incorporates genomic and eQTL data in identifying disease gene candidates and uses gene network and ontology data to score them based upon the strength of their relationship to the disease in question. AVAILABILITY AND IMPLEMENTATION: http://zdzlab.einstein.yu.edu/1/pga.html. CONTACT: zhengdong.zhang@einstein.yu.edu. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Integrated Rare Variant-Based Risk Gene Prioritization in Disease Case-Control Sequencing Studies.
Lin JR, Zhang Q, Cai Y, Morrow BE, Zhang ZD (2017) PLoS Genet 13(12):e1007142. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · DISEASE STUDY · GENETIC VARIATION

ABSTRACT: Rare variants of major effect play an important role in human complex diseases and can be discovered by sequencing-based genome-wide association studies. Here, we introduce an integrated approach that combines the rare variant association test with gene network and phenotype information to identify risk genes implicated by rare variants for human complex diseases. Our data integration method follows a 'discovery-driven' strategy without relying on prior knowledge about the disease and thus maintains the unbiased character of genome-wide association studies. Simulations reveal that our method can outperform a widely-used rare variant association test method by 2 to 3 times. In a case study of a small disease cohort, we uncovered putative risk genes and the corresponding rare variants that may act as genetic modifiers of congenital heart disease in 22q11.2 deletion syndrome patients. These variants were missed by a conventional approach that relied on the rare variant association test alone.

◸ JOURNAL HIGHLIGHTED ARTICLE
Integrated Post-Gwas Analysis Sheds New Light on the Disease Mechanisms of Schizophrenia.
Lin JR, Cai Y, Zhang Q, Zhang W, Nogales-Cadenas R, Zhang ZD (2016) Genetics 204(4):1587-1600. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · DISEASE STUDY

ABSTRACT: Schizophrenia is a severe mental disorder with a large genetic component. Recent genome-wide association studies (GWAS) have identified many schizophrenia-associated common variants. For most of the reported associations, however, the underlying biological mechanisms are not clear. The critical first step for their elucidation is to identify the most likely disease genes as the source of the association signals. Here, we describe a general computational framework of post-GWAS analysis for complex disease gene prioritization. We identify 132 putative schizophrenia risk genes in 76 risk regions spanning 120 schizophrenia-associated common variants, 78 of which have not been recognized as schizophrenia disease genes by previous GWAS. Even more significantly, 29 of them are outside the risk regions, likely under regulation of transcriptional regulatory elements contained therein. These putative schizophrenia risk genes are transcriptionally active in both brain and the immune system, and highly enriched among cellular pathways, consistent with leading pathophysiological hypotheses about the pathogenesis of schizophrenia. With their involvement in distinct biological processes, these putative schizophrenia risk genes, with different association strengths, show distinctive temporal expression patterns, and play specific biological roles during brain development.

Prioritization of Schizophrenia Risk Genes by a Network-Regularized Logistic Regression Method.
Zhang W, Lin JR, Nogales-Cadenas R, Zhang Q, Cai Y, Zhang ZD (2016) Lecture Notes in Bioinformatics 9565:434-445. JOURNAL REPRINT ANALYTICAL METHOD · DISEASE STUDY

ABSTRACT: Schizophrenia (SCZ) is a severe mental disorder with a large genetic component. While recent large-scale microarray- and sequencing-based genome wide association studies have made significant progress toward finding SCZ risk variants and genes of subtle effect, the interactions among them were not considered in those studies. Using a protein-protein interaction network both in our regression model and to generate a SCZ gene subnetwork, we developed an analytical framework with Logit-Lapnet, the graphical Laplacian-regularized logistic regression, for whole exome sequencing (WES) data analysis to detect SCZ gene subnetworks. Using simulated data from sequencing-based association study, we compared the performances of Logit-Lapnet with other logistic regression (LR)-based models. We use Logit-Lapnet to prioritize genes according to their coefficients and select top-ranked genes as seeds to generate the gene sub-network that is associated to SCZ. The comparison demonstrated not only the applicability but also better performance of Logit-Lapnet to score disease risk genes using sequencing-based association data. We applied our method to SCZ whole exome sequencing data and selected top-ranked risk genes, the majority of which are either known SCZ genes or genes potentially associated with SCZ. We then used the seed genes to construct SCZ gene subnetworks. This result demonstrates that by rank-ing gene according to their disease contributions our method scores and thus prioritiz-es disease risk genes for further investigation. An implementation of our approach in MATLAB is freely available for download at:
http://zdzlab.einstein.yu.edu/1/publications/LapNet-MATLAB.zip.

SubNet: A Java Application for Subnetwork Extraction.
Lemetre C, Zhang Q, Zhang ZD (2013) Bioinformatics 29(19):2509-11. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE · SYSTEMS BIOLOGY

ABSTRACT: SUMMARY: The extraction of targeted subnetworks is a powerful way to identify functional modules and pathways within complex networks. Here, we present SubNet, a Java-based stand-alone program for extracting subnetworks, given a basal network and a set of selected nodes. Designed with a graphical user-friendly interface, SubNet combines four different extraction methods, which offer the possibility to interrogate a biological network according to the question investigated. Of note, we developed a method based on the highly successful Google PageRank algorithm to extract the subnetwork using the node centrality metric, to which possible node weights of the selected genes can be incorporated. AVAILABILITY: http://www.zdzlab.org/1/subnet.html

Identification of Genomic Indels and Structural Variations Using Split Reads.
Zhang ZD, Du J, Lam H, Abyzov A, Urban AE, Snyder M, Gerstein M (2011) BMC Genomics 12:375. JOURNAL PUBMED REPRINT ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: BACKGROUND: Recent studies have demonstrated the genetic significance of insertions, deletions, and other more complex structural variants (SVs) in the human population. With the development of the next-generation sequencing technologies, high-throughput surveys of SVs on the whole-genome level have become possible. Here we present split-read identification, calibrated (SRiC), a sequence-based method for SV detection. RESULTS: We start by mapping each read to the reference genome in standard fashion using gapped alignment. Then to identify SVs, we score each of the many initial mappings with an assessment strategy designed to take into account both sequencing and alignment errors (e.g. scoring more highly events gapped in the center of a read). All current SV calling methods have multilevel biases in their identifications due to both experimental and computational limitations (e.g. calling more deletions than insertions). A key aspect of our approach is that we calibrate all our calls against synthetic data sets generated from simulations of high-throughput sequencing (with realistic error models). This allows us to calculate sensitivity and the positive predictive value under different parameter-value scenarios and for different classes of events (e.g. long deletions vs. short insertions). We run our calculations on representative data from the 1000 Genomes Project. Coupling the observed numbers of events on chromosome 1 with the calibrations gleaned from the simulations (for different length events) allows us to construct a relatively unbiased estimate for the total number of SVs in the human genome across a wide range of length scales. We estimate in particular that an individual genome contains ~670,000 indels/SVs. CONCLUSIONS: Compared with the existing read-depth and read-pair approaches for SV identification, our method can pinpoint the exact breakpoints of SV events, reveal the actual sequence content of insertions, and cover the whole size spectrum for deletions. Moreover, with the advent of the third-generation sequencing technologies that produce longer reads, we expect our method to be even more useful.

ACT: Aggregation and Correlation Toolbox for Analyses of Genome Tracks.
Jee J, Rozowsky J, Yip KY, Lochovsky L, Bjornson R, Zhong G, Zhang Z, Fu Y, Wang J, Weng Z, Gerstein M (2011) Bioinformatics 27(8):1152-4. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: UNLABELLED: We have implemented aggregation and correlation toolbox (ACT), an efficient, multifaceted toolbox for analyzing continuous signal and discrete region tracks from high-throughput genomic experiments, such as RNA-seq or ChIP-chip signal profiles from the ENCODE and modENCODE projects, or lists of single nucleotide polymorphisms from the 1000 genomes project. It is able to generate aggregate profiles of a given track around a set of specified anchor points, such as transcription start sites. It is also able to correlate related tracks and analyze them for saturation--i.e. how much of a certain feature is covered with each new succeeding experiment. The ACT site contains downloadable code in a variety of formats, interactive web servers (for use on small quantities of data), example datasets, documentation and a gallery of outputs. Here, we explain the components of the toolbox in more detail and apply them in various contexts. AVAILABILITY: ACT is available at http://act.gersteinlab.org CONTACT: pi@gersteinlab.org.

Detection of Copy Number Variation from Array Intensity and Sequencing Read Depth Using a Stepwise Bayesian Model.
Zhang ZD, Gerstein MB (2010) BMC Bioinformatics 11:539. JOURNAL PUBMED REPRINT ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: BACKGROUND: Copy number variants (CNVs) have been demonstrated to occur at a high frequency and are now widely believed to make a significant contribution to the phenotypic variation in human populations. Array-based comparative genomic hybridization (array-CGH) and newly developed read-depth approach through ultrahigh throughput genomic sequencing both provide rapid, robust, and comprehensive methods to identify CNVs on a whole-genome scale. RESULTS: We developed a Bayesian statistical analysis algorithm for the detection of CNVs from both types of genomic data. The algorithm can analyze such data obtained from PCR-based bacterial artificial chromosome arrays, high-density oligonucleotide arrays, and more recently developed high-throughput DNA sequencing. Treating parameters--e.g., the number of CNVs, the position of each CNV, and the data noise level--that define the underlying data generating process as random variables, our approach derives the posterior distribution of the genomic CNV structure given the observed data. Sampling from the posterior distribution using a Markov chain Monte Carlo method, we get not only best estimates for these unknown parameters but also Bayesian credible intervals for the estimates. We illustrate the characteristics of our algorithm by applying it to both synthetic and experimental data sets in comparison to other segmentation algorithms. CONCLUSIONS: In particular, the synthetic data comparison shows that our method is more sensitive than other approaches at low false positive rates. Furthermore, given its Bayesian origin, our method can also be seen as a technique to refine CNVs identified by fast point-estimate methods and also as a framework to integrate array-CGH and sequencing data with other CNV-related biological knowledge, all through informative priors.

Integrating Sequencing Technologies in Personal Genomics: Optimal Low Cost Reconstruction of Structural Variants.
Du J, Bjornson RD, Zhang ZD, Kong Y, Snyder M, Gerstein MB (2009) PLoS Comput Biol 5(7):e1000432. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD

ABSTRACT: The goal of human genome re-sequencing is obtaining an accurate assembly of an individual's genome. Recently, there has been great excitement in the development of many technologies for this (e.g. medium and short read sequencing from companies such as 454 and SOLiD, and high-density oligo-arrays from Affymetrix and NimbelGen), with even more expected to appear. The costs and sensitivities of these technologies differ considerably from each other. As an important goal of personal genomics is to reduce the cost of re-sequencing to an affordable point, it is worthwhile to consider optimally integrating technologies. Here, we build a simulation toolbox that will help us optimally combine different technologies for genome re-sequencing, especially in reconstructing large structural variants (SVs). SV reconstruction is considered the most challenging step in human genome re-sequencing. (It is sometimes even harder than de novo assembly of small genomes because of the duplications and repetitive sequences in the human genome.) To this end, we formulate canonical problems that are representative of issues in reconstruction and are of small enough scale to be computationally tractable and simulatable. Using semi-realistic simulations, we show how we can combine different technologies to optimally solve the assembly at low cost. With mapability maps, our simulations efficiently handle the inhomogeneous repeat-containing structure of the human genome and the computational complexity of practical assembly algorithms. They quantitatively show how combining different read lengths is more cost-effective than using one length, how an optimal mixed sequencing strategy for reconstructing large novel SVs usually also gives accurate detection of SNPs/indels, how paired-end reads can improve reconstruction efficiency, and how adding in arrays is more efficient than just sequencing for disentangling some complex SVs. Our strategy should facilitate the sequencing of human genomes at maximum accuracy and low cost.

PEMer: A Computational Framework with Simulation-Based Error Models for Inferring Genomic Structural Variants from Massive Paired-End Sequencing Data.
Korbel JO, Abyzov A, Mu XJ, Carriero N, Cayting P, Zhang Z, Snyder M, Gerstein MB (2009) Genome Biol 10(2):R23. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: Personal-genomics endeavors, such as the 1000 Genomes project, are generating maps of genomic structural variants by analyzing ends of massively sequenced genome fragments. To process these we developed Paired-End Mapper (PEMer; http://sv.gersteinlab.org/pemer). This comprises an analysis pipeline, compatible with several next-generation sequencing platforms; simulation-based error models, yielding confidence-values for each structural variant; and a back-end database. The simulations demonstrated high structural variant reconstruction efficiency for PEMer's coverage-adjusted multi-cutoff scoring-strategy and showed its relative insensitivity to base-calling errors.

PeakSeq Enables Systematic Scoring of ChIP-seq Experiments Relative to Controls.
Rozowsky J, Euskirchen G, Auerbach RK, Zhang ZD, Gibson T, Bjornson R, Carriero N, Snyder M, Gerstein MB (2009) Nat Biotechnol 27(1):66-75. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD · SOFTWARE / PIPELINE / DATABASE

ABSTRACT: Chromatin immunoprecipitation (ChIP) followed by tag sequencing (ChIP-seq) using high-throughput next-generation instrumentation is fast, replacing chromatin immunoprecipitation followed by genome tiling array analysis (ChIP-chip) as the preferred approach for mapping of sites of transcription-factor binding and chromatin modification. Using two deeply sequenced data sets for human RNA polymerase II and STAT1, each with matching input-DNA controls, we describe a general scoring approach to address unique challenges in ChIP-seq data analysis. Our approach is based on the observation that sites of potential binding are strongly correlated with signal peaks in the control, likely revealing features of open chromatin. We develop a two-pass strategy called PeakSeq to compensate for this. A two-pass strategy compensates for signal caused by open chromatin, as revealed by inclusion of the controls. The first pass identifies putative binding sites and compensates for genomic variation in the 'mappability' of sequences. The second pass filters out sites not significantly enriched compared to the normalized control, computing precise enrichments and significances. Our scoring procedure enables us to optimize experimental design by estimating the depth of sequencing required for a desired level of coverage and demonstrating that more than two replicates provides only a marginal gain in information.

Modeling ChIP Sequencing in Silico with Applications.
Zhang ZD, Rozowsky J, Snyder M, Chang J, Gerstein M (2008) PLoS Comput Biol 4(8):e1000158. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD

ABSTRACT: ChIP sequencing (ChIP-seq) is a new method for genomewide mapping of protein binding sites on DNA. It has generated much excitement in functional genomics. To score data and determine adequate sequencing depth, both the genomic background and the binding sites must be properly modeled. To develop a computational foundation to tackle these issues, we first performed a study to characterize the observed statistical nature of this new type of high-throughput data. By linking sequence tags into clusters, we show that there are two components to the distribution of tag counts observed in a number of recent experiments: an initial power-law distribution and a subsequent long right tail. Then we develop in silico ChIP-seq, a computational method to simulate the experimental outcome by placing tags onto the genome according to particular assumed distributions for the actual binding sites and for the background genomic sequence. In contrast to current assumptions, our results show that both the background and the binding sites need to have a markedly nonuniform distribution in order to correctly model the observed ChIP-seq data, with, for instance, the background tag counts modeled by a gamma distribution. On the basis of these results, we extend an existing scoring approach by using a more realistic genomic-background model. This enables us to identify transcription-factor binding sites in ChIP-seq data in a statistically rigorous fashion.

Statistical Analysis of the Genomic Distribution and Correlation of Regulatory Elements in the ENCODE Regions.
Zhang ZD, Paccanaro A, Fu Y, Weissman S, Weng Z, Chang J, Snyder M, Gerstein MB (2007) Genome Res 17(6):787-97. JOURNAL PUBMED REPRINT POSTER WEBSITE ANALYTICAL METHOD · FUNCTIONAL GENOMICS

ABSTRACT: The comprehensive inventory of functional elements in 44 human genomic regions carried out by the ENCODE Project Consortium enables for the first time a global analysis of the genomic distribution of transcriptional regulatory elements. In this study we developed an intuitive and yet powerful approach to analyze the distribution of regulatory elements found in many different ChIP-chip experiments on a 10 approximately 100-kb scale. First, we focus on the overall chromosomal distribution of regulatory elements in the ENCODE regions and show that it is highly nonuniform. We demonstrate, in fact, that regulatory elements are associated with the location of known genes. Further examination on a local, single-gene scale shows an enrichment of regulatory elements near both transcription start and end sites. Our results indicate that overall these elements are clustered into regulatory rich "islands" and poor "deserts." Next, we examine how consistent the nonuniform distribution is between different transcription factors. We perform on all the factors a multivariate analysis in the framework of a biplot, which enhances biological signals in the experiments. This groups transcription factors into sequence-specific and sequence-nonspecific clusters. Moreover, with experimental variation carefully controlled, detailed correlations show that the distribution of sites was generally reproducible for a specific factor between different laboratories and microarray platforms. Data sets associated with histone modifications have particularly strong correlations. Finally, we show how the correlations between factors change when only regulatory elements far from the transcription start sites are considered.

A Supervised Hidden Markov Model Framework for Efficiently Segmenting Tiling Array Data in Transcriptional and chIP-chip Experiments: Systematically Incorporating Validated Biological Knowledge.
Du J, Rozowsky JS, Korbel JO, Zhang ZD, Royce TE, Schultz MH, Snyder M, Gerstein M (2006) Bioinformatics 22(24):3016-24. JOURNAL PUBMED REPRINT WEBSITE ANALYTICAL METHOD

ABSTRACT: MOTIVATION: Large-scale tiling array experiments are becoming increasingly common in genomics. In particular, the ENCODE project requires the consistent segmentation of many different tiling array datasets into 'active regions' (e.g. finding transfrags from transcriptional data and putative binding sites from ChIP-chip experiments). Previously, such segmentation was done in an unsupervised fashion mainly based on characteristics of the signal distribution in the tiling array data itself. Here we propose a supervised framework for doing this. It has the advantage of explicitly incorporating validated biological knowledge into the model and allowing for formal training and testing. METHODOLOGY: In particular, we use a hidden Markov model (HMM) framework, which is capable of explicitly modeling the dependency between neighboring probes and whose extended version (the generalized HMM) also allows explicit description of state duration density. We introduce a formal definition of the tiling-array analysis problem, and explain how we can use this to describe sampling small genomic regions for experimental validation to build up a gold-standard set for training and testing. We then describe various ideal and practical sampling strategies (e.g. maximizing signal entropy within a selected region versus using gene annotation or known promoters as positives for transcription or ChIP-chip data, respectively). RESULTS: For the practical sampling and training strategies, we show how the size and noise in the validated training data affects the performance of an HMM applied to the ENCODE transcriptional and ChIP-chip experiments. In particular, we show that the HMM framework is able to efficiently process tiling array data as well as or better than previous approaches. For the idealized sampling strategies, we show how we can assess their performance in a simulation framework and how a maximum entropy approach, which samples sub-regions with very different signal intensities, gives the maximally performing gold-standard. This latter result has strong implications for the optimum way medium-scale validation experiments should be carried out to verify the results of the genome-scale tiling array experiments.

Evidence for Improved DNA Repair in the Long-Lived Bowhead Whale.
Firsanov D, Zacher M, Tian X, Sformo TL, Zhao Y, Tombline G, Lu JY, Zheng Z, Perelli L, Gurreri E, Zhang L, Guo J, Korotkov A, Volobaev V, Biashad SA, Zhang Z, Heid J, Maslov AY, Sun S, Wu Z, Gigas J, Hillpot EC, Martinez JC, Lee M, Williams A, Gilman A, Hamilton N, Strelkova E, Haseljic E, Patel A, Straight ME, Miller N, Ablaeva J, Tam LM, Couderc C, Hoopmann MR, Moritz RL, Fujii S, Pelletier A, Hayman DJ, Liu H, Cai Y, Leung AKL, Zhang Z, Nelson CB, Abegglen LM, Schiffman JD, Gladyshev VN, Maley CC, Modesti M, Genovese G, Simons MJP, Vijg J, Seluanov A, Gorbunova V (2025) Nature 648(8094):717-725. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: At more than 200 years, the maximum lifespan of the bowhead whale exceeds that of all other mammals. The bowhead is also the second-largest animal on Earth1, reaching over 80,000 kg. Despite its very large number of cells and long lifespan, the bowhead is not highly cancer-prone, an incongruity termed Peto's paradox2. Here, to understand the mechanisms that underlie the cancer resistance of the bowhead whale, we examined the number of oncogenic hits required for malignant transformation of whale primary fibroblasts. Unexpectedly, bowhead whale fibroblasts required fewer oncogenic hits to undergo malignant transformation than human fibroblasts. However, bowhead whale cells exhibited enhanced DNA double-strand break repair capacity and fidelity, and lower mutation rates than cells of other mammals. We found the cold-inducible RNA-binding protein CIRBP to be highly expressed in bowhead fibroblasts and tissues. Bowhead whale CIRBP enhanced both non-homologous end joining and homologous recombination repair in human cells, reduced micronuclei formation, promoted DNA end protection, and stimulated end joining in vitro. CIRBP overexpression in Drosophila extended lifespan and improved resistance to irradiation. These findings provide evidence supporting the hypothesis that, rather than relying on additional tumour suppressor genes to prevent oncogenesis3-5, the bowhead whale maintains genome integrity through enhanced DNA repair. This strategy, which does not eliminate damaged cells but faithfully repairs them, may be contributing to the exceptional longevity and low cancer incidence in the bowhead whale.

Identification of Functional Rare Coding Variants in IGF-1 Gene in Humans with Exceptional Longevity.
Ali A, Zhang ZD, Gao T, Aleksic S, Gavathiotis E, Barzilai N, Milman S (2025) Sci Rep 15(1):10199. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: Diminished signaling via insulin/insulin-like growth factor-1 (IGF-1) axis is associated with longevity in different model organisms. IGF-1 gene is highly conserved across species, with only few evolutionary changes identified in it. Despite its potential role in regulating lifespan, no coding variants in IGF-1 have been reported in human longevity cohorts to date. This study investigated the whole exome sequencing data from 2,108 individuals in a cohort of Ashkenazi Jewish centenarians, their offspring, and controls without familial longevity to identify functional IGF-1 coding variants. We identified two likely functional coding variants IGF-1:p.Ile91Leu and IGF-1:p.Ala118Thr in our longevity cohort. Notably, a centenarian specific novel variant IGF-1:p.Ile91Leu was located at the binding interface of IGF-1-IGF-1R, whereas IGF-1:p.Ala118Thr was significantly associated with lower circulating levels of IGF-1. We performed extended all-atom molecular dynamics simulations to evaluate the impact of Ile91Leu on stability, binding dynamics and energetics of IGF-1 bound to IGF-1R. The IGF-1:p.Ile91Leu formed less stable interactions with IGF-1R's critical binding pocket residues and demonstrated lower binding affinity at the extracellular binding site compared to wild-type IGF-1. Our findings suggest that IGF-1:p.Ile91Leu and IGF-1:p.Ala118Thr variants attenuate IGF-1R activity by impairing IGF-1 binding and diminishing the circulatory levels of IGF-1, respectively. Consequently, diminished IGF-1 signaling resulting from these variants may contribute to exceptional longevity in humans.

Inducible Aging in Hydra Oligactis Implicates Sexual Reproduction, Loss of Stem Cells, and Genome Maintenance as Major Pathways.
Sun S, White RR, Fischer KE, Zhang Z, Austad SN, Vijg J (2020) Geroscience 42(4):1119-1132. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: Freshwater polyps of the genus Hydra do not age. However, temperature stress induces aging and a shift from reproduction by asexual budding to sexual gamete production in a cold-sensitive (CS) strain of H. oligactis. We sequenced the transcriptome of a male CS strain before and after this life history shift and compared changes in gene expression relative to those seen in a cold-resistant (CR) strain that does not undergo a life history shift in response to altered temperature. We found that the switch from non-aging asexual reproduction to aging and sexual reproduction involves upregulation of genes not only involved in gametogenesis but also genes involved in cellular senescence, apoptosis, and DNA repair accompanied by a downregulation of genes involved in stem cell maintenance. These results suggest that aging is a byproduct of sexual reproduction-associated cellular reprogramming and underscore the power of these H. oligactis strains to identify intrinsic mechanisms of aging.

The Nutritional Environment Determines Which and How Intestinal Stem Cells Contribute to Homeostasis and Tumorigenesis.
Li W, Zimmerman SE, Peregrina K, Houston M, Mayoral J, Zhang J, Maqbool S, Zhang Z, Cai Y, Ye K, Augenlicht LH (2019) Carcinogenesis 40(8):937-946. JOURNAL PUBMED REPRINT CELL BIOLOGY

ABSTRACT: Sporadic colon cancer accounts for approximately 80% of colorectal cancer (CRC) with high incidence in Western societies strongly linked to long-term dietary patterns. A unique mouse model for sporadic CRC results from feeding a purified rodent Western-style diet (NWD1) recapitulating intake for the mouse of common nutrient risk factors each at its level consumed in higher risk Western populations. This causes sporadic large and small intestinal tumors in wild-type mice at an incidence and frequency similar to that in humans. NWD1 perturbs intestinal cell maturation and Wnt signaling throughout villi and colonic crypts and decreases mouse Lgr5hi intestinal stem cell contribution to homeostasis and tumor development. Here we establish that NWD1 transcriptionally reprograms Lgr5hi cells, and that nutrients are interactive in reprogramming. Furthermore, the DNA mismatch repair pathway is elevated in Lgr5hi cells by lower vitamin D3 and/or calcium in NWD1, paralleled by reduced accumulation of relevant somatic mutations detected by single-cell exome sequencing. In compensation, NWD1 also reprograms Bmi1+ cells to function and persist as stem-like cells in mucosal homeostasis and tumor development. The data establish the key role of the nutrient environment in defining the contribution of two different stem cell populations to both mucosal homeostasis and tumorigenesis. This raises important questions regarding impact of variable human diets on which and how stem cell populations function in the human mucosa and give rise to tumors. Moreover, major differences reported in turnover of human and mouse crypt base stem cells may be linked to their very different nutrient exposures.

SIRT6 Is Responsible for More Efficient DNA Double-Strand Break Repair in Long-Lived Species.
Tian X, Firsanov D, Zhang Z, Cheng Y, Luo L, Tombline G, Tan R, Simon M, Henderson S, Steffan J, Goldfarb A, Tam J, Zheng K, Cornwell A, Johnson A, Yang JN, Mao Z, Manta B, Dang W, Zhang Z, Vijg J, Wolfe A, Moody K, Kennedy BK, Bohmann D, Gladyshev VN, Seluanov A, Gorbunova V (2019) Cell 177(3):622-638.e22. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY · COMPARATIVE GENOMICS

ABSTRACT: DNA repair has been hypothesized to be a longevity determinant, but the evidence for it is based largely on accelerated aging phenotypes of DNA repair mutants. Here, using a panel of 18 rodent species with diverse lifespans, we show that more robust DNA double-strand break (DSB) repair, but not nucleotide excision repair (NER), coevolves with longevity. Evolution of NER, unlike DSB, is shaped primarily by sunlight exposure. We further show that the capacity of the SIRT6 protein to promote DSB repair accounts for a major part of the variation in DSB repair efficacy between short- and long-lived species. We dissected the molecular differences between a weak (mouse) and a strong (beaver) SIRT6 protein and identified five amino acid residues that are fully responsible for their differential activities. Our findings demonstrate that DSB repair and SIRT6 have been optimized during the evolution of longevity, which provides new targets for anti-aging interventions.

Global, Integrated Analysis of Methylomes and Transcriptomes from Laser Capture Microdissected Bronchial and Alveolar Cells in Human Lung.
Dong X, Shi M, Lee M, Toro R, Gravina S, Han W, Yasuda S, Wang T, Zhang Z, Vijg J, Suh Y, Spivack SD (2018) Epigenetics 13(3):264-274. JOURNAL PUBMED REPRINT CELL BIOLOGY · EPIGENOMICS

ABSTRACT: Gene regulatory analysis of highly diverse human tissues in vivo is essentially constrained by the challenge of performing genome-wide, integrated epigenetic and transcriptomic analysis in small selected groups of specific cell types. Here we performed genome-wide bisulfite sequencing and RNA-seq from the same small groups of bronchial and alveolar cells isolated by laser capture microdissection from flash-frozen lung tissue of 12 donors and their peripheral blood T cells. Methylation and transcriptome patterns differed between alveolar and bronchial cells, while each of these epithelia showed more differences from mesodermally-derived T cells. Differentially methylated regions (DMRs) between alveolar and bronchial cells tended to locate at regulatory regions affecting promoters of 4,350 genes. A large number of pathways enriched for these DMRs including GTPase signal transduction, cell death, and skeletal muscle. Similar patterns of transcriptome differences were observed: 4,108 differentially expressed genes (DEGs) enriched in GTPase signal transduction, inflammation, cilium assembly, and others. Prioritizing using DMR-DEG regulatory network, we highlighted genes, e.g., ETS1, PPARG, and RXRG, at prominent alveolar vs. bronchial cell discriminant nodes. Our results show that multi-omic analysis of small, highly specific cells is feasible and yields unique physiologic loci distinguishing human lung cell types in situ.

Translation Fidelity Coevolves with Longevity.
Ke Z, Mallik P, Johnson AB, Luna F, Nevo E, Zhang ZD, Gladyshev VN, Seluanov A, Gorbunova V (2017) Aging Cell 16(5):988-993. JOURNAL PUBMED REPRINT AGING · CELL BIOLOGY

ABSTRACT: Whether errors in protein synthesis play a role in aging has been a subject of intense debate. It has been suggested that rare mistakes in protein synthesis in young organisms may result in errors in the protein synthesis machinery, eventually leading to an increasing cascade of errors as organisms age. Studies that followed generally failed to identify a dramatic increase in translation errors with aging. However, whether translation fidelity plays a role in aging remained an open question. To address this issue, we examined the relationship between translation fidelity and maximum lifespan across 17 rodent species with diverse lifespans. To measure translation fidelity, we utilized sensitive luciferase-based reporter constructs with mutations in an amino acid residue critical to luciferase activity, wherein misincorporation of amino acids at this mutated codon re-activated the luciferase. The frequency of amino acid misincorporation at the first and second codon positions showed strong negative correlation with maximum lifespan. This correlation remained significant after phylogenetic correction, indicating that translation fidelity coevolves with longevity. These results give new life to the role of protein synthesis errors in aging: Although the error rate may not significantly change with age, the basal rate of translation errors is important in defining lifespan across mammals.

Cyclin C Regulates Adipogenesis by Stimulating Transcriptional Activity of CCAAT/enhancer-binding Protein Α.
Song Z, Xiaoli AM, Zhang Q, Zhang Y, Yang EST, Wang S, Chang R, Zhang ZD, Yang G, Strich R, Pessin JE, Yang F (2017) J Biol Chem 292(21):8918-8932. JOURNAL PUBMED REPRINT CELL BIOLOGY

ABSTRACT: Brown adipose tissue is important for maintaining energy homeostasis and adaptive thermogenesis in rodents and humans. As disorders arising from dysregulated energy metabolism, such as obesity and metabolic diseases, have increased, so has interest in the molecular mechanisms of adipocyte biology. Using a functional screen, we identified cyclin C (CycC), a conserved subunit of the Mediator complex, as a novel regulator for brown adipocyte formation. siRNA-mediated CycC knockdown (KD) in brown preadipocytes impaired the early transcriptional program of differentiation, and genetic KO of CycC completely blocked the differentiation process. RNA sequencing analyses of CycC-KD revealed a critical role of CycC in activating genes co-regulated by peroxisome proliferator activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα). Overexpression of PPARγ2 or addition of the PPARγ ligand rosiglitazone rescued the defects in CycC-KO brown preadipocytes and efficiently activated the PPARγ-responsive promoters in both WT and CycC-KO cells, suggesting that CycC is not essential for PPARγ transcriptional activity. In contrast, CycC-KO significantly reduced C/EBPα-dependent gene expression. Unlike for PPARγ, overexpression of C/EBPα could not induce C/EBPα target gene expression in CycC-KO cells or rescue the CycC-KO defects in brown adipogenesis, suggesting that CycC is essential for C/EBPα-mediated gene activation. CycC physically interacted with C/EBPα, and this interaction was required for C/EBPα transactivation domain activity. Consistent with the role of C/EBPα in white adipogenesis, CycC-KD also inhibited differentiation of 3T3-L1 cells into white adipocytes. Together, these data indicate that CycC activates adipogenesis in part by stimulating the transcriptional activity of C/EBPα.

INK4 Locus of the Tumor-Resistant Rodent, the Naked Mole Rat, Expresses a Functional p15/p16 Hybrid Isoform.
Tian X, Azpurua J, Ke Z, Augereau A, Zhang ZD, Vijg J, Gladyshev VN, Gorbunova V, Seluanov A (2015) Proc Natl Acad Sci U S A 112(4):1053-8. JOURNAL PUBMED REPRINT CELL BIOLOGY

ABSTRACT: The naked mole rat (Heterocephalus glaber) is a long-lived and tumor-resistant rodent. Tumor resistance in the naked mole rat is mediated by the extracellular matrix component hyaluronan of very high molecular weight (HMW-HA). HMW-HA triggers hypersensitivity of naked mole rat cells to contact inhibition, which is associated with induction of the INK4 (inhibitors of cyclin dependent kinase 4) locus leading to cell-cycle arrest. The INK4a/b locus is among the most frequently mutated in human cancer. This locus encodes three distinct tumor suppressors: p15(INK4b), p16(INK4a), and ARF (alternate reading frame). Although p15(INK4b) has its own ORF, p16(INK4a) and ARF share common second and third exons with alternative reading frames. Here, we show that, in the naked mole rat, the INK4a/b locus encodes an additional product that consists of p15(INK4b) exon 1 joined to p16(INK4a) exons 2 and 3. We have named this isoform pALT(INK4a/b) (for alternative splicing). We show that pALT(INK4a/b) is present in both cultured cells and naked mole rat tissues but is absent in human and mouse cells. Additionally, we demonstrate that pALT(INK4a/b) expression is induced during early contact inhibition and upon a variety of stresses such as UV, gamma irradiation-induced senescence, loss of substrate attachment, and expression of oncogenes. When overexpressed in naked mole rat or human cells, pALT(INK4a/b) has stronger ability to induce cell-cycle arrest than either p15(INK4b) or p16(INK4a). We hypothesize that the presence of the fourth product, pALT(INK4a/b) of the INK4a/b locus in the naked mole rat, contributes to the increased resistance to tumorigenesis of this species.