Biology subjects

Gems, D.

Publications and source records attributed to Gems, D..

12 recordsLinked to original sources

bioRxiv2026

Strong inhibition of insulin/IGF-1 signaling in early-mid adulthood compresses morbidity, but in later life accelerates aging

Reduced insulin/IGF-1 signaling (IIS) can greatly extend lifespan in C. elegans. However, its effects on the duration of healthy life (healthspan) remain unclear, with several reports of either morbidity expansion or scaled effects, though none of morbidity compression. Moreover, life-extension by IIS reduction is particularly inter-individually variable within populations, confounding efforts to understand the intra-individual biology of such interventions. Here, we performed a longitudinal investigation at individual nematode resolution, of IIS reduction on aging-related health and lifespan, through temporally-controlled auxin-induced degradation (AID) of the DAF-2 insulin/IGF-1 receptor. Our results show how inter-individual variation in aging rate within control populations explains the complex demographic effects of age-specific DAF-2 AID on population lifespan. Strikingly, adult-limited IIS reduction causes an inter-individually homogeneous increase in lifespan (reducing Gompertz rather than {beta}) that is driven by healthspan expansion and compression of morbidity. Unexpectedly, cessation of DAF-2 AID in decrepit elderly individuals rejuvenates locomotory capacity and extends lifespan, showing that higher levels of IIS are optimal for health and survival towards the end of life. We also document a memory effect of transient IIS reduction during early adulthood, that is sufficient to fully extend lifespan (+189% median lifespan). Together, these findings demonstrate that both lifespan and healthspan can be maximized by appropriate temporal and directional modulation of IIS.

genetics↗

bioRxiv2026

Mutation of eat-2 in C. elegans is not a reliable model for dietary restriction studies

Dietary restriction (DR) extends lifespan in many animal species. In C. elegans, Eat mutants with pharyngeal defects that impair feeding exhibit reduced growth rate and fertility and are typically long-lived, suggesting a DR effect. We report that Eat mutant longevity is largely or wholly a consequence of suppression of feeding activity-dependent infection of the pharynx by their E. coli food source. eat-2 mutants, widely used as a DR model, were among only 2/8 Eat mutants tested whose longevity were to any degree independent of bacterial infection. Moreover, among Eat mutants, phenotypic indicators of reduced nutrition correlated with one another, yet not with longevity. These findings document how, if infection is excluded, Eat mutants experience reduced nutrition, but in most cases not longevity, i.e. life-extending DR effects are not typical of Eat mutants. Thus, eat-2 longevity is partially due to infection resistance rather than DR, and residual, pharyngeal infection-independent longevity (contributing [~]40% of the total increase in lifespan) could reflect DR, or alternatively some other consequence of their nicotinic acetylcholine receptor defect.

physiology↗

bioRxiv2026

The Strehler-Mildvan mortality correlation arises from changes in the variability of ageing

As global human life expectancy continues to rise, accompanying increases in healthspan that prevent morbidity expansion become increasingly imperative. Population lifespan can increase in distinct ways, for instance through rectangularization (steepening) or triangularization (flattening) of survival curves. These two demographic changes, particularly rectangularization, occur frequently across human and model organism populations, yet their biological determinants and effects on healthspan and morbidity are largely unknown. Notably, these modes of life-extension occur when parameters of the Gompertz mortality model (capturing exponential age-increases in mortality rate) change inversely, a widely-reported phenomenon known as the Strehler-Mildvan correlation - whose biological basis also remains unexplained. We therefore investigated longitudinal health, morbidity and lifespan in 30 Caenorhabditis elegans cohorts using multiple life-extension protocols. We report that survival curve rectangularization results from healthspan expansion in short-lived population members, whereas triangularization (which primarily extends the curve tail) from healthspan and morbidity expansion in long-lived population members. Interestingly, rectangularization and triangularization respectively decrease and increase inter-individual variation in the aging process, and the mode of life-extension that occurs depends on levels of existing variation. Notably, triangularization was more effective at extending lifespan without morbidity expansion. Analysis of fruit fly and mouse data show that these biodemographic dynamics are also largely evolutionarily conserved.

physiology↗

bioRxiv2025

A hierarchy of causes of death in senescent C. elegans

In experimental gerontology, lifespan is often interpreted as a metric of the rate of the overall aging process. However, interventions that increase lifespan can result from suppression of one or more individual late-life pathologies. Here we show how, in the nematode Caenorhabditis elegans, such pathologies can compete in a hierarchical fashion to cause death, such that removal of one cause of death can unmask another. Under standard culture conditions, a major cause of death in elderly C. elegans is infection by their bacterial food source. We report that only when such infection is prevented is lifespan extended by suppression of a second senescent pathology, teratoma-like uterine tumors. Thus, as in mammals, lifespan in wild-type C. elegans can be limited by naturally-occurring neoplasia. By contrast, blocking bacterial infection attenuated the life-shortening effects of vitellogenesis, and did not unmask a life-shortening effect of distal gonad degeneration. Thus, depending on the masking or unmasking of competing causes of mortality in the hierarchy of causes of death, nematode lifespan limitation in different contexts can reflect action of distinct life-limiting senescent pathologies. This underscores how increases in lifespan do not necessarily reflect a reduction in overall aging rate.

pathology↗

bioRxiv2025

Condition-dependent effects of knockdown of autophagy on C. elegans longevity

Autophagy is proposed to protect against aging by clearing damaged cellular constituents. In line with this several life-extending interventions in model organisms show some degree of autophagy dependence. In C. elegans, inhibiting autophagy can shorten, lengthen or have no effect on lifespan. Differences between published findings likely reflect variability in experimental conditions. Here we investigate the condition dependence of effects on lifespan of RNA-mediated interference (RNAi) knockdown of autophagy pathway components. Effects on interventions causing a strong Age (increased lifespan) phenotype were examined: mainly mutation of daf-2 (insulin/IGF-1 receptor), but also suppression of germline development by mutation of glp-1. Factors varied included daf-2 mutant allele class, atg gene, temperature and presence of 5-fluoro-2-deoxyuridine (FUDR). Effects on lifespan of atg RNAi proved to be highly condition dependent. Notably, for most atg genes tested lifespan was not usually reduced more in the long-lived mutant than in the wild-type control. Greater suppression was seen at 20{degrees}C for certain atg genes with daf-2(e1368) but not daf-2(e1370). At 25{degrees}C, little reduction in lifespan was seen. However, atg-18 knockdown behaved differently, suppressing daf-2 Age under all conditions, suggesting possible pleiotropic action. In wild-type C. elegans, FUDR at a high concentration caused knockdown of several atg genes to increase lifespan. Thus, depending on experimental conditions, atg knockdown can increase, decrease or have no effect on daf-2 Age. Condition dependent effects were also seen with respect to glp-1 Age. The lack of suppression of daf-2 Age by atg RNAi under most conditions questions the importance of autophagy for this phenotype. Moreover, condition dependence of effects creates a risk of possible condition selection bias.

genetics↗

bioRxiv2025

Slow Gompertzian aging in long-lived C. elegans results from expansion of decrepitude, not decelerated aging

The Gompertz equation describes exponential age-increases in animal mortality rate arising from biological aging. Its parameters, and {beta}, are widely used to evaluate lifespan-extending interventions and human mortality patterns: it is assumed that reduction in {beta} corresponds to deceleration of aging rate, and reduction in to reduced aging-independent mortality. However, this view has never been empirically validated. We therefore investigated the biological basis of and {beta}, by simultaneous quantification of mortality and age-related health in long-lived populations of the nematode Caenorhabditis elegans. We show that reduction in {beta} arises not from decelerated aging but expansion of decrepitude in longer-lived individuals, whereas reduction in arises from decelerated aging. This empirical re-evaluation of Gompertzian aging inverts and challenges long-standing ideas in the biodemography of aging.

physiology↗

bioRxiv2024

Machine learning predicts lifespan and underlying causes of death in aging C. elegans

Senescence (aging) leads to senescent pathology that causes death, and genes control aging by determining such pathology. Here we investigate how senescent pathology mediates the effect of genotype on lifespan in C. elegans by means of a data-driven approach, using machine learning (ML). To achieve this we gathered extensive data on how diverse determinants of lifespan (sex, nutrition, genotype) affect patterns of age-related pathology. Our findings show that different life-extending treatments result in distinct patterns of suppression of senescent pathology. By analysing the differential effects on pathology and lifespan, our ML models were able to predict >70% of lifespan variation. Extent of pathology in the pharynx and intestine were the most important predictors of lifespan, arguing that elderly C. elegans die in part due to late-life disease in these organs. Notably, the mid-life pathogenetic burst characteristic of hermaphrodite senescence is absent from males.

genetics↗

bioRxiv2020

C. elegans hermaphrodites undergo semelparous reproductive death

Ageing in the nematode Caenorhabditis elegans is unusual in terms of the severity and early onset of senescent pathology, particularly affecting organs involved in reproduction (Ezcurra et al., 2018; Garigan et al., 2002; Herndon et al., 2002). In post-reproductive C. elegans hermaphrodites, intestinal biomass is converted into yolk leading to intestinal atrophy and yolk steatosis (Ezcurra et al., 2018; Sornda et al., 2019). We recently showed that post-reproductive mothers vent yolk which functions as a milk (yolk milk), supporting larval growth that is consumed by larvae (Kern et al., 2020). This form of massive reproductive effort involving biomass repurposing leading to organ degeneration is characteristic of semelparous organisms (i.e. that exhibit only a single reproductive episode) ranging from monocarpic plants to Pacific salmon where it leads to rapid death (reproductive death) (Finch, 1990; Gems et al., 2020). Removal of the germline greatly increases lifespan in both C. elegans and Pacific salmon, in the latter case by suppressing semelparous reproductive death (Hsin and Kenyon, 1999; Robertson, 1961). Here we present evidence that reproductive death occurs in C. elegans, and that it is suppressed by germline removal, leading to extension of lifespan. Comparing three Caenorhabditis sibling species pairs with hermaphrodites and females, we show that lactation and massive early pathology only occurs in the former. In each case, hermaphrodites are shorter lived and only in hermaphrodites does germline removal markedly increase lifespan. Semelparous reproductive death has previously been viewed as distinct from ageing; however, drawing on recent theories of ageing (Blagosklonny, 2006; de Magalhaes and Church, 2005; Maklakov and Chapman, 2019), we argue that it involves exaggerated versions of programmatic mechanisms that to a smaller extent contribute to ageing in non-semelparous species. Thus, despite the presence of reproductive death, mechanisms of ageing in C. elegans are informative about ageing in general.

genetics↗

bioRxiv2020

C. elegans provide milk for their young

Adult C. elegans hermaphrodites exhibit severe senescent pathology that begins to develop within days of reaching sexual maturity (Ezcurra et al., 2018; Garigan et al., 2002; Herndon et al., 2002; Wang et al., 2018). For example, after depletion of self-sperm, intestinal biomass is converted into yolk leading to intestinal atrophy and yolk steatosis (pseudocoelomic lipoprotein pools, PLPs) (Ezcurra et al., 2018; Garigan et al., 2002; Herndon et al., 2002; Sornda et al., 2019). These senescent pathologies are promoted by insulin/IGF-1 signalling (IIS), which also shortens lifespan (Ezcurra et al., 2018; Kenyon, 2010). This pattern of rapid and severe pathology in organs linked to reproduction is reminiscent of semelparous organisms where massive reproductive effort leads to rapid death (reproductive death) as in Pacific salmon (Finch, 1990; Gems et al., 2020). Moreover, destructive conversion of somatic biomass to support reproduction is a hallmark of reproductive death (Gems et al., 2020). Yet arguing against the occurrence of reproductive death in C. elegans is the apparent futility of post-reproductive yolk production. Here we show that this effort is not futile, since post-reproductive mothers vent yolk through their vulva, which is consumed by progeny and supports their growth; thus vented yolk functions as a milk, and C. elegans mothers exhibit a form of lactation. Moreover, IIS promotes lactation, thereby effecting a costly process of resource transfer from postreproductive mothers to offspring. These results support the view that C. elegans hermaphrodites exhibit reproductive death involving a self-destructive process of lactation that is promoted by IIS. They also provide new insight into how the strongly life-shortening effects of IIS in C. elegans evolved.

genetics↗

bioRxiv2017

Autophagy-dependent gut-to-yolk biomass conversion generates visceral polymorbidity in aging C. elegans

Aging (senescence) is characterized by the development of numerous pathologies, some of which limit lifespan. Key to understanding aging is discovery of the mechanisms (etiologies) that cause senescent pathology. In Caenorhabditis elegans a major senescent pathology of unknown etiology is atrophy of its principal metabolic organ, the intestine. Here we identify a cause of not only this pathology, but also of yolky lipid accumulation and redistribution (a form of senescent obesity): autophagy-mediated conversion of intestinal biomass into yolk. Inhibiting intestinal autophagy or vitellogenesis rescues both visceral pathologies, and can also extend lifespan. This defines a disease syndrome leading to polymorbidity and contributing to late-life mortality. Activation of gut-to-yolk biomass conversion by insulin/IGF-1 signaling (IIS) promotes reproduction and senescence. This illustrates how major, IIS-promoted senescent pathologies in C. elegans can originate not from damage accumulation, but from continued action of a wild-type function (vitellogenesis), consistent with the recently proposed hyperfunction theory of aging.

physiology↗

bioRxiv2017

LFASS: Label-Free Automated Survival Scoring for High-Throughput Nematode Assays

Caenorhabditis elegans is an excellent model for high-throughput experimental approaches, but lacks a robust, versatile and automated means to pinpoint time of death. Here we describe an automated, label-free, high-throughput method using death-associated fluorescence to monitor nematode survival, which we apply to stress and infection resistance assays. We demonstrate its use to define correlations between age, longevity and stress-resistance, and reveal an autophagy-dependent increase in acute stress resistance in early adulthood.

genetics↗

bioRxiv2017

Monsters in the uterus: A parthenogenetic quasi-program causes teratoma-like tumors during aging in wild-type C. elegans

Many diseases whose frequency increases with advancing age are caused by aging (senescence), but the mechanisms of senescence remain poorly understood. According to G.C. Williams and M.V. Blagosklonny, a major etiological determinant of senescence is late-life, wild-type gene action and non-adaptive execution of biological programs (or quasi-programs). These generate a wide range of senescent pathologies causing illness and death. Here we investigate the etiology of a prominent senescent pathology in the nematode C. elegans, uterine tumors, in the light of the Williams Blagosklonny theory. Uterine tumors develop from unfertilized, immature oocytes which execute incomplete embryogenetic programs. This includes extensive endomitosis, leading to formation of chromatin masses and cellular hypertrophy. The starting point of pathogenesis is exhaustion of sperm stocks. The timing of this transition between program and quasi-program can be altered by blocking sperm production (causing earlier tumors) or supplying additional sperm by mating (delaying tumor onset). Other pathophysiological determinants are yolk consumption by tumors, and bacterial proliferation within tumors. Uterine tumors resemble mammalian ovarian teratomas (tera, Greek: monster) in that both develop from oocytes that fail to mature after meiosis I, and both are the result of quasi-programs. Moreover, older but not younger uterine tumors show expression of markers of later embryogenesis, i.e. are teratoma-like. These results show how uterine tumors in C. elegans form as the result of run-on of embryogenetic quasi-programs. They also suggest fundamental etiological equivalence between teratoma and some forms of senescent pathology, insofar as both are caused by quasi-programs.

developmental biology↗