2021 Articles

Gladyshev VN, Kritchevsky SB, Clarke SG, Cuervo AM, Fiehn O, de Magalhães JP, Mau T, Maes M, Moritz RL, Niedernhofer LJ, Schaftingen EV, Tranah GJ, Walsh K, Yura Y, Zhang B, Cummings SR (2021) Molecular damage in aging. Nature Aging, 1, 1096–1106

Abstract Cellular metabolism and environmental interactions generate molecular damage affecting all levels of biological organization. Accumulation of this damage over time is thought to have a central role in the aging process. Insufficient attention has been paid to the role of molecular damage in aging-related phenotypes, particularly in humans, in part because of the difficulty in measuring its various forms. Recently, omics approaches have been developed that begin to address this challenge, because they can assess a sizable proportion of age-related damage at the level of small molecules, proteins, RNA, DNA, organelles and cells. This Review describes the concept of molecular damage in aging and discusses its diverse aspects from theoretical models to experimental approaches. Measurement of multiple types of damage enables studies of the role of damage in aging and lays a foundation for testing interventions that reduce the burden of molecular damage, thereby targeting aging. More Information

Trapp A, Kerepesi C & Gladyshev VN (2021) Profiling epigenetic age in single cells. Nature Aging, 1, 1189–1201

Abstract DNA methylation of a defined set of CpG dinucleotides emerged as a critical and precise biomarker of the aging process. Multi-variate machine learning models, known as epigenetic clocks, can exploit quantitative changes in the methylome to predict the age of bulk tissue with remarkable accuracy. However, intrinsic sparsity and digitized methylation in individual cells have so far precluded the assessment of aging in single cell data. Here, we present scAge, a probabilistic approach to determine the epigenetic age of single cells, and validate our results in mice. scAge tissue-specific and multi-cell type single cell clocks correctly recapitulate chronological age of the original tissue, while uncovering the inherent heterogeneity that exists at the single-cell level. The data suggest that while tissues age in a coordinated fashion, some cells age more or less rapidly than others. We show that individual embryonic stem cells exhibit an age close to zero, that certain stem cells in a tissue show a reduced age compared to their chronological age, and that early embryogenesis is associated with the reduction of epigenetic age of individual cells, the latter supporting a natural rejuvenation event during gastrulation. scAge is both robust against the low coverage that is characteristic of single cell sequencing techniques and is flexible for studying any cell type and vertebrate organism of interest. This study demonstrates for the first time the potential for accurate epigenetic age profiling at single-cell resolution. More Information

Zhang B, Lee DE, Trapp A, Tyshkovskiy A, Lu AT, Bareja A, Kerepesi C, Katz LH, Shindyapina AV, Dmitriev SE, Baht GS, Horvath S, Gladyshev VN (2021) Multi-omic rejuvenation and lifespan extension upon exposure to youthful circulation. bioRxiv, 10.1101/2021.11.11.468258

Abstract Heterochronic parabiosis (HPB) is known for its functional rejuvenation effects across several mouse tissues. However, its impact on the biological age of organisms and their long-term health remains unknown. Here, we performed extended (3-month) HPB, followed by a 2-month detachment period of anastomosed pairs. Old detached mice exhibited improved physiological parameters and lived longer than control isochronic mice. HPB drastically reduced the biological age of blood and liver based on epigenetic analyses across several clock models on two independent platforms; remarkably, this rejuvenation effect persisted even after 2 months of detachment. Transcriptomic and epigenomic profiles of anastomosed mice showed an intermediate phenotype between old and young, suggesting a comprehensive multi-omic rejuvenation effect. In addition, old HPB mice showed transcriptome changes opposite to aging, but akin to several lifespan-extending interventions. Altogether, we reveal that long-term HPB can decrease the biological age of mice, in part through long-lasting epigenetic and transcriptome remodeling, culminating in the extension of lifespan and healthspan. More Information

Trapp A & Gladyshev VN (2021) Cost-effective epigenetic age profiling in shallow methylation sequencing data. bioRxiv, 10.1101/2021.10.25.465778

Abstract There is a critical need for robust, high-throughput assays of biological aging trajectories. Among various approaches, epigenetic aging clocks emerged as reliable molecular trackers of the aging process. However, current methods for epigenetic age profiling are inherently costly and lack throughput. Here, we leverage the scAge framework for accurate prediction of biological age from very few bisulfite sequencing reads in bulk samples, thereby enabling drastic (100-1,000-fold) reduction in sequencing costs per sample. Our approach permits age assessment based on distinct assortments of CpG sites in different samples, without the need for targeted site enrichment or specialized reagents. We demonstrate the efficacy of this method to quantify the age of mouse blood samples across independent cohorts, identify the effect of calorie restriction as an attenuator of the aging process, and discern rejuvenation upon cellular reprogramming. We propose that this framework may be used for epigenetic age prediction in extremely high-throughput applications, enabling robust, large-scale and inexpensive interventions testing and age profiling. More Information

Griffin PT, Kane AE, Trapp A, Li J, McNamara MS, Meer MV, MacArthur MR, Mitchell SJ, Mueller AL, Colleen C, Vera DL, Kerepesi C, Hooten NN, Mitchell JR, Evans MK, Gladyshev VN, Sinclair DA (2021) Ultra-cheap and scalable epigenetic age predictions with TIME-Seq. bioRxiv, 10.1101/2021.10.25.465725

Abstract Epigenetic “clocks” based on DNA methylation (DNAme) are the most robust and widely employed aging biomarker. They have been built for numerous species and reflect gold-standard interventions that extend lifespan. However, conventional methods for measuring epigenetic clocks are expensive and low-throughput. Here, we describe Tagmentation-based Indexing for Methylation Sequencing (TIME-Seq) for ultra-cheap and scalable targeted methylation sequencing of epigenetic clocks and other DNAme biomarkers. Using TIME-Seq, we built and validated inexpensive epigenetic clocks based on genomic and ribosomal DNAme in hundreds of mice and human samples. We also discover it is possible to accurately predict age from extremely low-cost shallow sequencing (e.g., 10,000 reads) of TIME-Seq libraries using scAge, a probabilistic age-prediction algorithm originally applied to single cells. Together, these methods reduce the cost of DNAme biomarker analysis by more than two orders of magnitude, thereby expanding and democratizing their use in aging research, clinical trials, and disease diagnosis. More Information

Kerepesi C, Zhang B, Lee SL, Trapp A & Gladyshev VN (2021) Epigenetic clocks reveal a rejuvenation event during embryogenesis followed by aging. Science Advances 7, eabg6082.

Abstract The notion that the germ line does not age goes back to the 19th-century ideas of August Weismann. However, being metabolically active, the germ line accumulates damage and other changes over time, i.e., it ages. For new life to begin in the same young state, the germ line must be rejuvenated in the offspring. Here, we developed a multi-tissue epigenetic clock and applied it, together with other aging clocks, to track changes in biological age during mouse and human prenatal development. This analysis revealed a significant decrease in biological age, i.e., rejuvenation, during early stages of embryogenesis, followed by an increase in later stages. We further found that pluripotent stem cells do not age even after extensive passaging and that the examined epigenetic age dynamics is conserved across species. Overall, this study uncovers a natural rejuvenation event during embryogenesis and suggests that the minimal biological age (ground zero) marks the beginning of organismal aging. More Information

Shindyapina AV, Castro JP, Barbieri A, Strelkova OS, Paulo JA, Kerepesi C, Petrashen AP, Mariotti M, Meer M, Hu Y, Losyev G, Indzhykulian AA, Gygi SP, Sedivy JM, Manis JP & Gladyshev VN (2021) Aging predisposes B cells to malignancy by activating c-Myc and perturbing the genome and epigenome. bioRxiv, 10.1101/2021.02.23.432500.

Abstract Age is the single major risk factor for human cancer; however, naturally occurring cancers are rarely studied in aged animal models. Laboratory mouse strains spontaneously develop cancer with age and some predominantly die from B-cell lymphoma. Here, we uncover how B-cell lymphoma develops as a consequence of the aging immune system. We found that aged B cells undergo clonal expansions driven by genetic and epigenetic changes and established cell and spleen size as early markers of malignant transformation. High-throughput and omics assays of aged B cells and the use of mouse models revealed that c-Myc is a master regulator of B cell size and clonal expansion. A single-cell RNA-seq analysis suggested that clonal B cells originate from age-associated B cells, memory B cells that accumulate during aging. Further studies showed that c-Myc becomes activated in B cells in response to the aging microenvironment. Thus, c-Myc, aging environment, somatic mutations and the epigenome cooperate to give rise to clonal age-accelerated B cells, which we named Myc+ cells. We further show the relevance of this model to aged human B cells in blood and spleen. This study characterized a first mouse model that captures a natural transition of B cells to a prevalent type of cancer during aging. More Information

Ying K, Zhai R, Pyrkov TV, Shindyapina AV, Mariotti M, Fedichev PO, Shen X &; Gladyshev VN (2021) Genetic and phenotypic analysis of the causal relationship between aging and COVID-19. Communications Medicine 5, e2144.

Abstract Epidemiological studies revealed that the elderly and those with comorbidities are most affected by COVID-19, but it is important to investigate shared genetic mechanisms between COVID-19 risk and aging. We conducted a multi-instrument Mendelian Randomization analysis of multiple lifespan-related traits and COVID-19. Aging clock models were applied to the subjects with different COVID-19 conditions in the UK-Biobank cohort. We performed a bivariate genomic scan for age-related COVID-19 and Mendelian Randomization analysis of 389 immune cell traits to investigate their effect on lifespan and COVID-19 risk. We show that the genetic variation that supports longer life is significantly associated with the lower risk of COVID-19 infection and hospitalization. The odds ratio is 0.31 (P = 9.7 × 10−6) and 0.46 (P = 3.3 × 10−4), respectively, per additional 10 years of life. We detect an association between biological age acceleration and future incidence and severity of COVID-19 infection. Genetic profiling of age-related COVID-19 infection indicates key contributions of Notch signaling and immune system development. We reveal a negative correlation between the effects of immune cell traits on lifespan and COVID-19 risk. We find that lower B-cell CD19 levels are indicative of an increased risk of COVID-19 and decreased life expectancy, which is further validated by COVID-19 clinical data. Our analysis suggests that the factors that accelerate aging lead to an increased COVID-19 risk and point to the importance of Notch signaling and B cells in both. Interventions that target these factors to reduce biological age may reduce the risk of COVID-19. More Information

Jin L, Tang Q, Hu S, Chen Z, Zhou X, Zeng B, Wang Y, He M, Li Y, Gui L, Shen L, Long K, Ma J, Wang X, Chen Z, Jiang Y, Tang G, Zhu L, Liu F, Zhang B, Huang Z, Li G, Li D, Gladyshev VN, Yin J, Gu Y, Li X & Li M (2021) A pig BodyMap transcriptome reveals diverse tissue physiologies and evolutionary dynamics of transcription. Nature Communications 12, 3715.

Abstract A comprehensive transcriptomic survey of pigs can provide a mechanistic understanding of tissue specialization processes underlying economically valuable traits and accelerate their use as a biomedical model. Here we characterize four transcript types (lncRNAs, TUCPs, miRNAs, and circRNAs) and protein-coding genes in 31 adult pig tissues and two cell lines. We uncover the transcriptomic variability among 47 skeletal muscles, and six adipose depots linked to their different origins, metabolism, cell composition, physical activity, and mitochondrial pathways. We perform comparative analysis of the transcriptomes of seven tissues from pigs and nine other vertebrates to reveal that evolutionary divergence in transcription potentially contributes to lineage-specific biology. Long-range promoter-enhancer interaction analysis in subcutaneous adipose tissues across species suggests evolutionarily stable transcription patterns likely attributable to redundant enhancers buffering gene expression patterns against perturbations, thereby conferring robustness during speciation. This study can facilitate adoption of the pig as a biomedical model for human biology and disease and uncovers the molecular bases of valuable traits. More Information

Zhang L, Dong X, Tian X, Lee M, Ablaeva J, Firsanov D, Lee SG, Maslov AY, Gladyshev VN, Seluanov A, Gorbunova V & Vijg J (2021) Maintenance of genome sequence integrity in long- and short-lived rodent species. Science Advances 7, eabj3284.

Abstract DNA mutations in somatic cells have been implicated in the causation of aging, with longer-lived species having a higher capacity to maintain genome sequence integrity than shorter-lived species. In an attempt to directly test this hypothesis, we used single-cell whole-genome sequencing to analyze spontaneous and bleomycin-induced somatic mutations in lung fibroblasts of four rodent species with distinct maximum life spans, including mouse, guinea pig, blind mole-rat, and naked mole-rat, as well as humans. As predicted, the mutagen-induced mutation frequencies inversely correlated with species-specific maximum life span, with the greatest difference observed between the mouse and all other species. These results suggest that long-lived species are capable of processing DNA damage in a more accurate way than short-lived species. More Information

Emmrich S, Tolibzoda Zakusilo F, Trapp A, Zhou X, Zhang Q, Irving EM, Drage MG, Zhang Z, Gladyshev VN, Seluanov A & Gorbunova V (2021) Ectopic cervical thymi and no thymic involution until midlife in naked mole rats. Aging Cell 20, e13477.

Abstract Immunosenescence is a hallmark of aging and manifests as increased susceptibility to infection, autoimmunity, and cancer in the elderly. One component of immunosenescence is thymic involution, age-associated shrinkage of the thymus, observed in all vertebrates studied to date. The naked mole rat (Heterocephalus glaber) has become an attractive animal model in aging research due to its extreme longevity and resistance to disease. Here, we show that naked mole rats display no thymic involution up to 11 years of age. Furthermore, we found large ectopic cervical thymi in addition to the canonical thoracic thymus, both being identical in their cell composition. The developmental landscape in naked mole rat thymi revealed overt differences from the murine T-cell compartment, most notably a decrease of CD4+ /CD8+ double-positive cells and lower abundance of cytotoxic effector T cells. Our observations suggest that naked mole rats display a delayed immunosenescence. Therapeutic interventions aimed at reversing thymic aging remain limited, underscoring the importance of understanding the cellular and molecular mechanisms behind a sustained immune function in the naked mole rat. More Information

Gladyshev VN (2021) The Ground Zero of Organismal Life and Aging. Trends in Molecular Medicine, 27, 11-19

Abstract Cells may naturally proceed or be forced to transition to a state with a radically lower biological age, that is, be rejuvenated. Examples are the conversion of somatic cells to induced pluripotent stem cells and rejuvenation of the germline with each generation. We posit that these processes converge to the same ‘ground zero’, the mid-embryonic state characterized by the lowest biological age where both organismal life and aging begin. It may also be related to the phylotypic state. The ground zero model clarifies the relationship between aging, development, rejuvenation, and de-differentiation, which are distinct throughout life. By extending the rejuvenation phase during early embryogenesis and editing the genome, it may be possible to achieve the biological age at the ground zero lower than that achieved naturally. More Information

Ristow M, Lee CH, De Bock K, Gladyshev VN, Hotamisligil GS & Manning BD (2021) James R. Mitchell (1971-2020). Cell Metabolism 33, 458-461

Abstract We are deeply saddened by the task of writing this memoriam for our beloved friend and colleague James (Jay) Mitchell, who passed away after a cycling accident on November 17 at the age of 49. Jay was absolutely unmatched in his creativity and ability to cross fields from molecular biology to physiology, from nutrition to genetics, and from epidemiology to surgery. He was among the first to crack the molecular code of the benefits of dietary restriction and defined unique pathways that opened many translational opportunities. He was a “science whisperer” in all stages of his career; this was his magical trademark. He was soft spoken but fiercely determined, incredibly resilient yet very kind and thoughtful, expressed strength with humility and content, and could relate to anyone in any walk of life and in any intellectual or artistic domain. He leaves behind his wife Elisabeth; his three sons, Lucas, Darius, and Ian; and an irreplaceable legacy as a husband, father, brother, son, friend, teacher, colleague, and most importantly, an invaluable human treasure. More Information

Augereau A, Mariotti M, Pousse M, Filipponi D, Libert F, Beck B, Gorbunova V, Gilson E & Gladyshev VN (2021) Naked mole rat TRF1 safeguards glycolytic capacity and telomere replication under low oxygen. Science Advances , 7, eabe0174

Abstract The naked mole rat (NMR), a long-lived and cancer-resistant rodent, is highly resistant to hypoxia. Here, using robust cellular models wherein the mouse telomeric protein TRF1 is substituted by NMR TRF1 or its mutant forms, we show that TRF1 supports maximal glycolytic capacity under low oxygen, shows increased nuclear localization and association with telomeres, and protects telomeres from replicative stress. We pinpoint this evolutionary gain of metabolic function to specific amino acid changes in the homodimerization domain of this protein. We further find that NMR TRF1 accelerates telomere shortening. These findings reveal an evolutionary strategy to adapt telomere biology for metabolic control under an extreme environment. More Information

Kaya A, Phua CZJ, Lee M, Wang L, Tyshkovskiy A, Ma S, Barre B, Liu W, Harrison BR, Zhao X, Zhou X, Wasko BM, Bammler TK, Promislow DE, Kaeberlein M & Gladyshev VN (2021) Evolution of natural lifespan variation and molecular strategies of extended lifespan. eLife, 10:e64860.

Abstract To understand the genetic basis and selective forces acting on longevity, it is useful to examine lifespan variation among closely related species, or ecologically diverse isolates of the same species, within a controlled environment. In particular, this approach may lead to understanding mechanisms underlying natural variation in lifespan. Here, we analyzed 76 ecologically diverse wild yeast isolates and discovered a wide diversity of replicative lifespan. Phylogenetic analyses pointed to genes and environmental factors that strongly interact to modulate the observed aging patterns. We then identified genetic networks causally associated with natural variation in replicative lifespan across wild yeast isolates, as well as genes, metabolites and pathways, many of which have never been associated with yeast lifespan in laboratory settings. In addition, a combined analysis of lifespan-associated metabolic and transcriptomic changes revealed unique adaptations to interconnected amino acid biosynthesis, glutamate metabolism and mitochondrial function in long-lived strains. Overall, our multi-omic and lifespan analyses across diverse isolates of the same species shows how gene-environment interactions shape cellular processes involved in phenotypic variation such as lifespan. More Information

Tian R, Han K, Geng Y, Yang C, Guo H, Shi C, Xu S, Yang G, Zhou X, Gladyshev VN, Liu X, Chopin LK, Fisher DO, Baker AM, Leiner NO, Fan G & Seim I (2021) A Chromosome-Level Genome of the Agile Gracile Mouse Opossum (Gracilinanus agilis). Molecular Biology and Evolution 13, evab162.

Abstract There are more than 100 species of American didelphid marsupials (opossums and mouse opossums). Limited genomic resources for didelphids exists, with only two publicly available genome assemblies compared with dozens in the case of their Australasian counterparts. This discrepancy impedes evolutionary and ecological research. To address this gap, we assembled a high-quality chromosome-level genome of the agile gracile mouse opossum (Gracilinanus agilis) using a combination of stLFR sequencing, polishing with mate-pair data, and anchoring onto pseudochromosomes using Hi-C. This species employs a rare life-history strategy, semelparity, and all G. agilis males and most females die at the end of their first breeding season after succumbing to stress and exhaustion. The 3.7-Gb chromosome-level assembly, with 92.6% anchored onto pseudochromosomes, has a scaffold N50 of 683.5 Mb and a contig N50 of 56.9 kb. The genome assembly shows high completeness, with a mammalian BUSCO score of 88.1%. Around 49.7% of the genome contains repetitive elements. Gene annotation yielded 24,425 genes, of which 83.9% were functionally annotated. The G. agilis genome is an important resource for future studies of marsupial biology, evolution, and conservation. More Information

Khera N, Santesmasses D, Kerepesi C & Gladyshev VN (2021) COVID-19 mortality rate in children is U-shaped. Aging 13, 19954-19962.

Abstract Children are known to be better protected from COVID-19 than adults, but their susceptibility patterns and the risk relative to other diseases are insufficiently defined. Here, we found that the COVID-19 mortality rate is U-shaped in childhood: it initially decreases, reaching the minimum at the ages 3-10 years, and then increases throughout life. All-cause mortality and mortality from other diseases, such as pneumonia and influenza, show a similar pattern; however, childhood mortality rates from COVID-19 are considerably lower than from other diseases, with the best relative protection achieved at the youngest ages. Consistent with this, the fraction of COVID-19 deaths among all deaths increases as a function of age throughout childhood and the entire life. We discuss implications of the elevated postnatal COVID-19 risk and lower childhood COVID-19 mortality compared to other diseases. More Information

Tian R, Han K, Geng Y, Yang C, Shi C, Thomas PB, Pearce C, Moffatt K, Ma S, Xu S, Yang G, Zhou X, Gladyshev VN, Liu X, Fisher DO, Chopin LK, Leiner NO, Baker AM, Fan G & Seim I (2021) A chromosome-level genome of Antechinus flavipes provides a reference for an Australian marsupial genus with male death after mating. Molecular Ecology Resources, 22 740-754.

Abstract The 15 species of small carnivorous marsupials that comprise the genus Antechinus exhibit semelparity, a rare life-history strategy in mammals where synchronized death occurs after one breeding season. Antechinus males, but not females, age rapidly (demonstrate organismal senescence) during the breeding season and show promise as new animal models of ageing. Some antechinus species are also threatened or endangered. Here, we report a chromosome-level genome of a male yellow-footed antechinus Antechinus flavipes. The genome assembly has a total length of 3.2 Gb with a contig N50 of 51.8 Mb and a scaffold N50 of 636.7 Mb. We anchored and oriented 99.7% of the assembly on seven pseudochromosomes and found that repetitive DNA sequences occupy 51.8% of the genome. Draft genome assemblies of three related species in the subfamily Phascogalinae, two additional antechinus species (Antechinus argentus and A. arktos) and the iteroparous sister species Murexia melanurus, were also generated. Preliminary demographic analysis supports the hypothesis that climate change during the Pleistocene isolated species in Phascogalinae and shaped their population size. A transcriptomic profile across the A. flavipes breeding season allowed us to identify genes associated with aspects of the male die-off. The chromosome-level A. flavipes genome provides a steppingstone to understanding an enigmatic life-history strategy and a resource to assist the conservation of antechinuses. More Information

Moldakozhayev A, Tskhay A & Gladyshev VN (2021) Applying deductive reasoning and the principles of particle physics to aging research. Aging, 13 22611-22622.

Abstract Aging is debatably one of the biggest mysteries for humanity, a process consisting of myriads of genetic, molecular, environmental, and stochastic deleterious events, leading to a progressive loss of organism functionality. Aging research currently lacks a common conceptual framework, and one challenge in establishing it is the fact that aging is a highly complex process. To help develop a framework of standard aging rules, we suggest the use of deductive reasoning based on particle physics’ principles. Specifically, the principles that we suggest applying to study aging are discreteness of processes, transformation as a result of interaction, and understanding of threshold. Using this framework, biological aging may be described as a sequence of highly discrete molecular transformations caused by a combination of various specific internal and external factors. Internal organismal function and interaction of an organism with the environment result in chronic accumulation of molecular damage and other deleterious consequences of metabolism and the consequent loss of system’s functionality. The loss of functionality occurs as a series of thresholds the organism reaches before it turns into an utterly non-functional state. We discuss how having a common ground may benefit aging research, introduce the logic of new principles and analyze specific examples of how this framework could be used to study aging and design longevity interventions. More Information

Egorov AA, Alexandrov AI, Urakov VN, Makeeva DS, Edakin RO, Kushchenko AS, Gladyshev VN, Kulakovskiy IV & Dmitriev SE. (2021) A standard knockout procedure alters expression of adjacent loci at the translational level. International Journal of Molecular Sciences49 11134.

Abstract The Saccharomyces cerevisiae gene deletion collection is widely used for functional gene annotation and genetic interaction analyses. However, the standard G418-resistance cassette used to produce knockout mutants delivers strong regulatory elements into the target genetic loci. To date, its side effects on the expression of neighboring genes have never been systematically assessed. Here, using ribosome profiling data, RT-qPCR, and reporter expression, we investigated perturbations induced by the KanMX module. Our analysis revealed significant alterations in the transcription efficiency of neighboring genes and, more importantly, severe impairment of their mRNA translation, leading to changes in protein abundance. In the ‘head-to-head’ orientation of the deleted and neighboring genes, knockout often led to a shift of the transcription start site of the latter, introducing new uAUG codon(s) into the expanded 5′ untranslated region (5′ UTR). In the ‘tail-to-tail’ arrangement, knockout led to activation of alternative polyadenylation signals in the neighboring gene, thus altering its 3′ UTR. These events may explain the so-called neighboring gene effect (NGE), i.e. false genetic interactions of the deleted genes. We estimate that in as much as ∼1/5 of knockout strains the expression of neighboring genes may be substantially (>2-fold) deregulated at the level of translation. More Information

Canter JA, Ernst SE, Peters KM, Carlson BA, Thielman NRJ, Grysczyk L, Udofe P, Yu Y, Cao L, Davis CD, Gladyshev VN, Hatfield DL & Tsuji PA (2021) Selenium and the 15kDa Selenoprotein Impact Colorectal Tumorigenesis by Modulating Intestinal Barrier Integrity. International Journal of Molecular Sciences, 22 10651.

Abstract Selenoproteins play important roles in many cellular functions and biochemical pathways in mammals. Our previous study showed that the deficiency of the 15 kDa selenoprotein (Selenof) significantly reduced the formation of aberrant crypt foci (ACF) in a mouse model of azoxymethane (AOM)-induced colon carcinogenesis. The objective of this study was to examine the effects of Selenof on inflammatory tumorigenesis, and whether dietary selenium modified these effects. For 20 weeks post-weaning, Selenof-knockout (KO) mice and littermate controls were fed diets that were either deficient, adequate or high in sodium selenite. Colon tumors were induced with AOM and dextran sulfate sodium. Surprisingly, KO mice had drastically fewer ACF but developed a similar number of tumors as their littermate controls. Expression of genes important in inflammatory colorectal cancer and those relevant to epithelial barrier function was assessed, in addition to structural differences via tissue histology. Our findings point to Selenof’s potential role in intestinal barrier integrity and structural changes in glandular and mucin-producing goblet cells in the mucosa and submucosa, which may determine the type of tumor developing. More Information

Omotoso O, Gladyshev VN & Zhou X (2021) Lifespan Extension in Long-Lived Vertebrates Rooted in Ecological Adaptation. Frontiers in Cell and Developmental Biology, 9 704966.

Abstract Contemporary studies on aging and longevity have largely overlooked the role that adaptation plays in lifespan variation across species. Emerging evidence indicates that the genetic signals of extended lifespan may be maintained by natural selection, suggesting that longevity could be a product of organismal adaptation. The mechanisms of adaptation in long-lived animals are believed to account for the modification of physiological function. Here, we first review recent progress in comparative biology of long-lived animals, together with the emergence of adaptive genetic factors that control longevity and disease resistance. We then propose that hitchhiking of adaptive genetic changes is the basis for lifespan changes and suggest ways to test this evolutionary model. As individual adaptive or adaptation-linked mutations/substitutions generate specific forms of longevity effects, the cumulative beneficial effect is largely nonrandom and is indirectly favored by natural selection. We consider this concept in light of other proposed theories of aging and integrate these disparate ideas into an adaptive evolutionary model, highlighting strategies in decoding genetic factors of lifespan control. More Information

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) Genomic expansion of Aldh1a1 protects beavers against high metabolic aldehydes from lipid oxidation. Cell Reports, 37 109965.

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. More Information

Santesmasses D & Gladyshev VN (2021) Pathogenic Variants in Selenoproteins and Selenocysteine Biosynthesis Machinery. International Journal of Molecular Sciences, 22 11593.

Abstract Selenium is incorporated into selenoproteins as the 21st amino acid selenocysteine (Sec). There are 25 selenoproteins encoded in the human genome, and their synthesis requires a dedicated machinery. Most selenoproteins are oxidoreductases with important functions in human health. A number of disorders have been associated with deficiency of selenoproteins, caused by mutations in selenoprotein genes or Sec machinery genes. We discuss mutations that are known to cause disease in humans and report their allele frequencies in the general population. The occurrence of protein-truncating variants in the same genes is also presented. We provide an overview of pathogenic variants in selenoproteins genes from a population genomics perspective. More Information

Bang J, Han M, Yoo TJ, Qiao L, Jung J, Na J, Carlson BA, Gladyshev VN, Hatfield DL, Kim JH, Kim LK & Lee BJ. (2021) Identification of Signaling Pathways for Early Embryonic Lethality and Developmental Retardation in Sephs1-/- Mice. International Journal of Molecular Sciences, 22 11647.

Abstract Selenophosphate synthetase 1 (SEPHS1) plays an essential role in cell growth and survival. However, the underlying molecular mechanisms remain unclear. In the present study, the pathways regulated by SEPHS1 during gastrulation were determined by bioinformatical analyses and experimental verification using systemic knockout mice targeting Sephs1. We found that the coagulation system and retinoic acid signaling were most highly affected by SEPHS1 deficiency throughout gastrulation. Gene expression patterns of altered embryo morphogenesis and inhibition of Wnt signaling were predicted with high probability at E6.5. These predictions were verified by structural abnormalities in the dermal layer of Sephs1-/- embryos. At E7.5, organogenesis and activation of prolactin signaling were predicted to be affected by Sephs1 knockout. Delay of head fold formation was observed in the Sephs1-/- embryos. At E8.5, gene expression associated with organ development and insulin-like growth hormone signaling that regulates organ growth during development was altered. Consistent with these observations, various morphological abnormalities of organs and axial rotation failure were observed. We also found that the gene sets related to redox homeostasis and apoptosis were gradually enriched in a time-dependent manner until E8.5. However, DNA damage and apoptosis markers were detected only when the Sephs1-/- embryos aged to E9.5. Our results suggest that SEPHS1 deficiency causes a gradual increase of oxidative stress which changes signaling pathways during gastrulation, and afterwards leads to apoptosis. More Information

Gerashchenko MV, Peterfi Z, Yim SH & Gladyshev VN (2021) Translation elongation rate varies among organs and decreases with age. Nucleic Acids Research, 49 e9

Abstract There has been a surge of interest towards targeting protein synthesis to treat diseases and extend lifespan. Despite the progress, few options are available to assess translation in live animals, as their complexity limits the repertoire of experimental tools to monitor and manipulate processes within organs and individual cells. It this study, we developed a labeling-free method for measuring organ- and cell-type-specific translation elongation rates in vivo. It is based on time-resolved delivery of translation initiation and elongation inhibitors in live animals followed by ribosome profiling. It also reports translation initiation sites in an organ-specific manner. Using this method, we found that the elongation rates differ more than 50% among mouse organs and determined them to be 6.8, 5.0 and 4.3 amino acids per second for liver, kidney, and skeletal muscle, respectively. We further found that the elongation rate is reduced by 20% between young adulthood and mid-life. Thus, translation, a major metabolic process in cells, is tightly regulated at the level of elongation of nascent polypeptide chains. More Information

Vorontsov IE, Egorov AA, Anisimova AS, Eliseeva IA, Makeev VJ, Gladyshev VN, Dmitriev SE & Kulakovskiy IV (2021) Assessing Ribosome Distribution Along Transcripts with Polarity Scores and Regression Slope Estimates. Methods in Molecular Medicine, 2252:269-294. doi: 10.1007/978-1-0716-1150-0_13

Abstract During translation, the rate of ribosome movement along mRNA varies. This leads to a non-uniform ribosome distribution along the transcript, depending on local mRNA sequence, structure, tRNA availability, and translation factor abundance, as well as the relationship between the overall rates of initiation, elongation, and termination. Stress, antibiotics, and genetic perturbations affecting composition and properties of translation machinery can alter the ribosome positional distribution dramatically. Here, we offer a computational protocol for analyzing positional distribution profiles using ribosome profiling (Ribo-Seq) data. The protocol uses papolarity, a new Python toolkit for the analysis of transcript-level short read coverage profiles. For a single sample, for each transcript papolarity allows for computing the classic polarity metric which, in the case of Ribo-Seq, reflects ribosome positional preferences. For comparison versus a control sample, papolarity estimates an improved metric, the relative linear regression slope of coverage along transcript length. This involves de-noising by profile segmentation with a Poisson model and aggregation of Ribo-Seq coverage within segments, thus achieving reliable estimates of the regression slope. The papolarity software and the associated protocol can be conveniently used for Ribo-Seq data analysis in the command-line Linux environment. Papolarity package is available through Python pip package manager. The source code is available at https://github.com/autosome-ru/papolarity. More Information

Mammalian Methylation Consortium (2021) Universal DNA methylation age across mammalian tissues. bioRxiv, 10.1101/2021.01.18.426733

Abstract Aging is often perceived as a degenerative process caused by random accrual of cellular damage over time. In spite of this, age can be accurately estimated by epigenetic clocks based on DNA methylation profiles from almost any tissue of the body. Since such pan-tissue epigenetic clocks have been successfully developed for several different species, it is difficult to ignore the likelihood that a defined and shared mechanism instead, underlies the aging process. To address this, we generated 10,000 methylation arrays, each profiling up to 37,000 cytosines in highly-conserved stretches of DNA, from over 59 tissue-types derived from 128 mammalian species. From these, we identified and characterized specific cytosines, whose methylation levels change with age across mammalian species. Genes associated with these cytosines are greatly enriched in mammalian developmental processes and implicated in age-associated diseases. From the methylation profiles of these age-related cytosines, we successfully constructed three highly accurate universal mammalian clocks for eutherians, and one universal clock for marsupials. The universal clocks for eutherians are similarly accurate for estimating ages (r>0.96) of any mammalian species and tissue with a single mathematical formula. Collectively, these new observations support the notion that aging is indeed evolutionarily conserved and coupled to developmental processes across all mammalian species – a notion that was long-debated without the benefit of this new and compelling evidence. More Information

Haghani A, Lu AT, Li CZ, Robeck TR, Belov K, Breeze CE, Brooke RT, Clarke S, Faulkes CG, Fei Z, Ferguson SH, Finno CJ, Gladyshev VN, Gorbunova V, Goya RG, Hogan AN, Hogg CJ, Hore TA, Kiaris H, Kordowitzki P, Banks G, Koski WR, Mozhui K, Naderi A, Ostrander EA, Parsons KM, Plassais J, Robbins J, Sears KE, Seluanov A, Steinman KJ, Szladovits B, Thompson MJ, Villar D, Wang N, Wilkinson GS, Young BG, Zhang J, Zoller JA, Ernst J, Yang XW, Raj K & S. Horvath. (2021) DNA Methylation Networks Underlying Mammalian Traits. bioRxiv, 10.1101/2021.03.16.435708.

Abstract Epigenetics has hitherto been studied and understood largely at the level of individual organisms. Here, we report a multi-faceted investigation of DNA methylation across 11,117 samples from 176 different species. We performed an unbiased clustering of individual cytosines into 55 modules and identified 31 modules related to primary traits including age, species lifespan, sex, adult species weight, tissue type and phylogenetic order. Analysis of the correlation between DNA methylation and species allowed us to construct phyloepigenetic trees for different tissues that parallel the phylogenetic tree. In addition, while some stable cytosines reflect phylogenetic signatures, others relate to age and lifespan, and in many cases responding to anti-aging interventions in mice such as caloric restriction and ablation of growth hormone receptors. Insights uncovered by this investigation have important implications for our understanding of the role of epigenetics in mammalian evolution, aging and lifespan. More Information

Gerashchenko MV & Gladyshev VN (2021) Measuring Organ-Specific Translation Elongation Rate in Mice. Methods in Molecular Biology 2252, 189-200.

Abstract Modern methods of genome editing enable the rapid generation of mouse models to study the regulation of protein synthesis. At the same time, few options are available to study translation in rodents as the animal’s complexity severely limits the repertoire of experimental tools. Here we describe a method to monitor translation in mice and other small animals. The technique is based on a ribosome profiling and specifically tailored toward measuring translation elongation. However, it can be easily applied for short upstream reading frames discovery. The advantage of this method is the ability to study translation in fully developed animals without extracting and subculturing cells, therefore, maintaining unperturbed physiological conditions. More Information

Choi DW, Roh YJ, Kim S, Lee HM, Kim M, Shin D, Park JH, Cho Y, Park HH, Ok YS, Kang D, Kim JH, Tarrago L, Danial NN, Gladyshev VN, Min PK & Lee BC (2021) Development of a novel fluorescent biosensor for dynamic monitoring of metabolic methionine redox status in cells and tissues. Biosensors and Bioelectronics 178, 113031.

Abstract Aberrant production of reactive oxygen species (ROS) leads to tissue damage accumulation, which is associated with a myriad of human pathologies. Although several sensors have been developed for ROS quantification, their applications for ROS-related human physiologies and pathologies still remain problematic due to the unstable nature of ROS. Herein, we developed Trx1-cpYFP-fRMsr (TYfR), a genetically-encoded fluorescent biosensor with the remarkable specificity and sensitivity toward fMetRO (free Methionine-R-sulfoxide), allowing for dynamic quantification of physiological levels of fMetRO, a novel indicator of ROS and methionine redox status in vitro and in vivo. Moreover, using the sensor, we observed a significant fMetRO enrichment in serum from patients with acute coronary syndrome, one of the most severe cardiovascular diseases, which becomes more evident following percutaneous coronary intervention. Collectively, this study proposes that fMetRO is a novel biomarker of tissue damage accumulation in ROS-associated human pathologies, and that TYfR is a promising tool for quantifying fMetRO with potentials in versatile applications. More Information