Budding yeast as a model organism to study the effects of age

Molecular mechanisms of nano-sized polystyrene plastics induced cytotoxicity and immunotoxicity in Eisenia fetida

Nanoplastics (NPs) are currently everywhere and environmental pollution by NPs is a pressing global problem. Nevertheless, until now, few studies have concentrated on the mechanisms and pathways of cytotoxic effects and immune dysfunction of NPs on soil organisms employing a multidimensional strategy. Hence, earthworm immune cells and immunity protein lysozyme (LZM) were selected as specific receptors to uncover the underlying mechanisms of cytotoxicity, genotoxicity, and immunotoxicity resulting from exposure to polystyrene nanoplastics (PS-NPs), and the binding mechanisms of PS-NPs-LZM interaction. Results on cells indicated that when earthworm immune cells were exposed to high-dose PS-NPs, it caused a notable rise in the release of reactive oxygen species (ROS), resulting in oxidative stress. PS-NPs exposure significantly decreased the cell viability of earthworm immune cells, inducing cytotoxicity through ROS-mediated oxidative stress pathway, and oxidative injury effects, including reduced antioxidant defenses, lipid peroxidation, DNA damage, and protein oxidation. Moreover, PS-NPs stress inhibited the intracellular LZM activity in immune cells, resulting in impaired immune function and immunotoxicity by activating the oxidative stress pathway mediated by ROS. The results from molecular studies revealed that PS-NPs binding destroyed the LZM structure and conformation, including secondary structure changes, protein skeleton unfolding/loosening, fluorescence sensitization, microenvironment changes, and particle size changes. Molecular docking suggested that PS-NPs combined with active center of LZM easier and inhibited the protein function more, and formed a hydrophobic interaction with TRP 62, a crucial amino acid residue closely associated with the function and conformation of LZM. This is also responsible for LZM conformational changes and functional inhibition /inactivation. These results of this research offer a fresh outlook on evaluating the detriment of NPs to the immune function of soil organisms using cellular and molecular strategies.

Fission-independent compartmentalization of mitochondria during budding yeast cell division

Lateral diffusion barriers compartmentalize membranes to generate polarity or asymmetrically partition membrane-associated macromolecules. Budding yeasts assemble such barriers in the endoplasmic reticulum (ER) and the outer nuclear envelope at the bud neck to retain aging factors in the mother cell and generate naïve and rejuvenated daughter cells. However, little is known about whether other organelles are similarly compartmentalized. Here, we show that the membranes of mitochondria are laterally compartmentalized at the bud neck and near the cell poles. The barriers in the inner mitochondrial membrane are constitutive, whereas those in the outer membrane form in response to stresses. The strength of mitochondrial diffusion barriers is regulated positively by spatial cues from the septin axis and negatively by retrograde (RTG) signaling. These data indicate that mitochondria are compartmentalized in a fission-independent manner. We propose that these diffusion barriers promote mitochondrial polarity and contribute to mitochondrial quality control.

Asymmetric T-cell division: insights from cutting-edge experimental techniques and implications for immunotherapy

Asymmetric cell division is a fundamental process conserved throughout evolution, employed by both prokaryotic and eukaryotic organisms. Its significance lies in its ability to govern cell fate and facilitate the generation of diverse cell types. Therefore, attaining a detailed mechanistic understanding of asymmetric cell division becomes essential for unraveling the complexities of cell fate determination in both healthy and pathological conditions. However, the role of asymmetric division in T-cell biology has only recently been unveiled. Here, we provide an overview of the T-cell asymmetric division field with the particular emphasis on experimental methods and models with the aim to guide the researchers in the selection of appropriate in vitro/in vivo models to study asymmetric division in T cells. We present a comprehensive investigation into the mechanisms governing the asymmetric division in various T-cell subsets underscoring the importance of the asymmetry in fate-determining factor segregation and transcriptional and epigenetic regulation. Furthermore, the intricate interplay of T-cell receptor signaling and the asymmetric division geometry are explored, shedding light on the spatial organization and the impact on cellular fate.

Study of Impacts of Two Types of Cellular Aging on the Yeast Bud Morphogenesis

Understanding the mechanisms of cellular aging processes is crucial for attempting to extend organismal lifespan and for studying age-related degenerative diseases. Yeast cells divide through budding, providing a classical biological model for studying cellular aging. With their powerful genetics, relatively short lifespan and well-established signaling pathways also found in animals, yeast cells offer valuable insights into the aging process. Recent experiments suggested the existence of two aging modes in yeast characterized by nucleolar and mitochondrial declines, respectively. In this study, by analyzing experimental data it was shown that cells evolving into those two aging modes behave differently when they are young. While buds grow linearly in both modes, cells that consistently generate spherical buds throughout their lifespan demonstrate greater efficacy in controlling bud size and growth rate at young ages. A three-dimensional chemical-mechanical model was developed and used to suggest and test hypothesized mechanisms of bud morphogenesis during aging. Experimentally calibrated simulations showed that tubular bud shape in one aging mode could be generated by locally inserting new materials at the bud tip guided by the polarized Cdc42 signal during the early stage of budding. Furthermore, the aspect ratio of the tubular bud could be stabilized during the late stage, as observed in experiments, through a reduction on the new cell surface material insertion or an expansion of the polarization site. Thus model simulations suggest the maintenance of new cell surface material insertion or chemical signal polarization could be weakened due to cellular aging in yeast and other cell types.

Mitochondrial protein and organelle quality control-Lessons from budding yeast

Mitochondria are essential for normal cellular function and have emerged as key aging determinants. Indeed, defects in mitochondrial function have been linked to cardiovascular, skeletal muscle and neurodegenerative diseases, premature aging, and age-linked diseases. Here, we describe mechanisms for mitochondrial protein and organelle quality control. These surveillance mechanisms mediate repair or degradation of damaged or mistargeted mitochondrial proteins, segregate mitochondria based on their functional state during asymmetric cell division, and modulate cellular fitness, the response to stress, and lifespan control in yeast and other eukaryotes.

Nuclear envelope budding and its cellular functions

The nuclear pore complex (NPC) has long been assumed to be the sole route across the nuclear envelope, and under normal homeostatic conditions it is indeed the main mechanism of nucleo-cytoplasmic transport. However, it has also been known that e.g. herpesviruses cross the nuclear envelope utilizing a pathway entitled nuclear egress or envelopment/de-envelopment. Despite this, a thread of observations suggests that mechanisms similar to viral egress may be transiently used also in healthy cells. It has since been proposed that mechanisms like nuclear envelope budding (NEB) can facilitate the transport of RNA granules, aggregated proteins, inner nuclear membrane proteins, and mis-assembled NPCs. Herein, we will summarize the known roles of NEB as a physiological and intrinsic cellular feature and highlight the many unanswered questions surrounding these intriguing nuclear events.

Sis2 regulates yeast replicative lifespan in a dose-dependent manner

Application of microfluidic platforms facilitated high-precision measurements of yeast replicative lifespan (RLS); however, comparative quantification of lifespan across strain libraries has been missing. Here we microfluidically measure the RLS of 307 yeast strains, each deleted for a single gene. Despite previous reports of extended lifespan in these strains, we found that 56% of them did not actually live longer than the wild-type; while the remaining 44% showed extended lifespans, the degree of extension was often different from what was previously reported. Deletion of SIS2 gene led to the largest RLS increase observed. Sis2 regulated yeast lifespan in a dose-dependent manner, implying a role for the coenzyme A biosynthesis pathway in lifespan regulation. Introduction of the human PPCDC gene in the sis2Δ background neutralized the lifespan extension. RNA-seq experiments revealed transcriptional increases in cell-cycle machinery components in sis2Δ background. High-precision lifespan measurement will be essential to elucidate the gene network governing lifespan.

Global analysis of aging-related protein structural changes uncovers enzyme-polymerization-based control of longevity

Aging is associated with progressive phenotypic changes. Virtually all cellular phenotypes are produced by proteins, and their structural alterations can lead to age-related diseases. However, we still lack comprehensive knowledge of proteins undergoing structural-functional changes during cellular aging and their contributions to age-related phenotypes. Here, we conducted proteome-wide analysis of early age-related protein structural changes in budding yeast using limited proteolysis-mass spectrometry (LiP-MS). The results, compiled in online ProtAge catalog, unraveled age-related functional changes in regulators of translation, protein folding, and amino acid metabolism. Mechanistically, we found that folded glutamate synthase Glt1 polymerizes into supramolecular self-assemblies during aging, causing breakdown of cellular amino acid homeostasis. Inhibiting Glt1 polymerization by mutating the polymerization interface restored amino acid levels in aged cells, attenuated mitochondrial dysfunction, and led to lifespan extension. Altogether, this comprehensive map of protein structural changes enables identifying mechanisms of age-related phenotypes and offers opportunities for their reversal.

Involvement of the Sch9/Rim15/Msn2 signaling pathway in the anti-aging activity of dendrobine from Dendrobium nobile Lindl. via modification of oxidative stress and autophagy

BACKGROUND

Aging is an important pathogenic factor of age-related diseases and has brought huge health threat and economic burden to the society. Dendrobium nobile Lindl., a valuable herb in China, promotes longevity according to the record of ancient Chinese materia medica. This study aimed to discover the material basis of D. nobile as an anti-aging herb and elucidate its action mechanism.

METHODS

K6001 yeast replicative lifespan assay was used to guide the isolation of D. nobile. The chronological lifespan assay of YOM36 yeast was further conducted to confirm the anti-aging activity of dendrobine. The mechanism in which dendrobine exerts anti-aging effect was determined by conducting anti-oxidative stress assay, quantitative real-time PCR, Western blot, measurements of anti-oxidant enzymes activities, determination of nuclear translocation of Rim15 and Msn2, and replicative lifespan assays of Δsod1, Δsod2, Δcat, Δgpx, Δatg2, Δatg32, and Δrim15 yeasts.

RESULTS

Under the guidance of K6001 yeast replicative lifespan system, dendrobine with anti-aging effect was isolated from D. nobile. The replicative and chronological lifespans of yeast were extended upon dendrobine treatment. In the study of action mechanism, dendrobine improved the survival rate of yeast under oxidative stress, decreased the levels of reactive oxygen species and malondialdehyde, and enhanced the enzyme activities and gene expression of superoxide dismutase and catalase, but it failed to elongate the replicative lifespans of Δsod1, Δsod2, Δcat, and Δgpx yeast mutants. Meanwhile, dendrobine enhanced autophagy occurrence in yeast but had no effect on the replicative lifespans of Δatg2 and Δatg32 yeast mutants. Moreover, the inhibition of Sch9 phosphorylation and the promotion of nuclear translocation of Rim15 and Msn2 were observed after treatment with denrobine. However, the effect of dendrobine disappeared from the Δrim15 yeast mutant after lifespan extension, oxidative stress reduction, and autophagy enhancement.

CONCLUSIONS

Dendrobine exerts anti-aging activity in yeast via the modification of oxidative stress and autophagy through the Sch9/Rim15/Msn2 signaling pathway. Our work provides a scientific basis for the exploitation of D. nobile as an anti-aging herb.

Selective retention of dysfunctional mitochondria during asymmetric cell division in yeast

Decline of mitochondrial function is a hallmark of cellular aging. To counteract this process, some cells inherit mitochondria asymmetrically to rejuvenate daughter cells. The molecular mechanisms that control this process are poorly understood. Here, we made use of matrix-targeted D-amino acid oxidase (Su9-DAO) to selectively trigger oxidative damage in yeast mitochondria. We observed that dysfunctional mitochondria become fusion-incompetent and immotile. Lack of bud-directed movements is caused by defective recruitment of the myosin motor, Myo2. Intriguingly, intact mitochondria that are present in the same cell continue to move into the bud, establishing that quality control occurs directly at the level of the organelle in the mother. The selection of healthy organelles for inheritance no longer works in the absence of the mitochondrial Myo2 adapter protein Mmr1. Together, our data suggest a mechanism in which the combination of blocked fusion and loss of motor protein ensures that damaged mitochondria are retained in the mother cell to ensure rejuvenation of the bud.

Threshold inclusion size triggers conversion of huntingtin to prion-like state that is reversible in newly born cells

Aggregation of mutant Huntingtin protein (mHtt) leads to neuronal cell death and human disease. We investigated the effect of inclusion formation on yeast cells. Previous work indicates that mHtt protein moves both in and out of inclusions, potentially undergoing refolding in the inclusion. However, the sustained influx of unfolded protein into an inclusion leads to a dramatic change from a phase-separated body to an irregular, less soluble form at a threshold inclusion size. Altered morphology was associated with a prion-like seeding that accelerated inclusion growth despite loss of soluble cytoplasmic protein. The structural change abolished exchange of material between the inclusion and the cytosol and resulted in early cell death. Affected cells continued to divide occasionally, giving rise to daughters with a similar phenotype. Most newly born cells were able to reverse the prion-like aggregation, restoring both soluble cytoplasmic protein and a normal inclusion structure.

The nexus between peroxisome abundance and chronological ageing in Saccharomyces cerevisiae

Ageing is characterized by changes in several cellular processes, with dysregulation of peroxisome function being one of them. Interestingly, the most conserved function of peroxisomes, ROS homeostasis, is strongly associated with ageing and age-associated pathologies. Previous studies have identified a role for peroxisomes in the regulation of chronological lifespan in yeast. In this study, we report the effect of altered peroxisome number on the chronological lifespan of yeast in two different growth media conditions. Three mutants, pex11, pex25 and pex27, defective in peroxisome fission, have been thoroughly investigated for the chronological lifespan. Reduced chronological lifespan of all the mutants was observed in peroxisome-inducing growth conditions. Furthermore, the combined deletion pex11pex25 exhibited the most prominent reduction in lifespan. Interestingly altered peroxisomal phenotype upon ageing was observed in all the cells. Increased ROS accumulation and reduced catalase activity was exhibited by chronologically aged mutant cells. Interestingly, mutants with reduced number of peroxisomes concomitantly also exhibited an accumulation of free fatty acids and increased number of lipid droplets. Taken together, our results reveal a previously unrealized effect of fission proteins in the chronological lifespan of yeast.

Gametogenesis: Exploring an Endogenous Rejuvenation Program to Understand Cellular Aging and Quality Control

Gametogenesis is a conserved developmental program whereby a diploid progenitor cell differentiates into haploid gametes, the precursors for sexually reproducing organisms. In addition to ploidy reduction and extensive organelle remodeling, gametogenesis naturally rejuvenates the ensuing gametes, leading to resetting of life span. Excitingly, ectopic expression of the gametogenesis-specific transcription factor Ndt80 is sufficient to extend life span in mitotically dividing budding yeast, suggesting that meiotic rejuvenation pathways can be repurposed outside of their natural context. In this review, we highlight recent studies of gametogenesis that provide emerging insight into natural quality control, organelle remodeling, and rejuvenation strategies that exist within a cell. These include selective inheritance, programmed degradation, and de novo synthesis, all of which are governed by the meiotic gene expression program entailing many forms of noncanonical gene regulation. Finally, we highlight critical questions that remain in the field and provide perspective on the implications of gametogenesis research on human health span.

Cellular enlargement - A new hallmark of aging?

Years of important research has revealed that cells heavily invest in regulating their size. Nevertheless, it has remained unclear why accurate size control is so important. Our recent study using hematopoietic stem cells (HSCs) in vivo indicates that cellular enlargement is causally associated with aging. Here, we present an overview of these findings and their implications. Furthermore, we performed a broad literature analysis to evaluate the potential of cellular enlargement as a new aging hallmark and to examine its connection to previously described aging hallmarks. Finally, we highlight interesting work presenting a correlation between cell size and age-related diseases. Taken together, we found mounting evidence linking cellular enlargement to aging and age-related diseases. Therefore, we encourage researchers from seemingly unrelated areas to take a fresh look at their data from the perspective of cell size.

Single-cell RNA-seq reveals early heterogeneity during aging in yeast

The budding yeast Saccharomyces cerevisiae (S. cerevisiae) has relatively short lifespan and is genetically tractable, making it a widely used model organism in aging research. Here, we carried out a systematic and quantitative investigation of yeast aging with single-cell resolution through transcriptomic sequencing. We optimized a single-cell RNA sequencing (scRNA-seq) protocol to quantitatively study the whole transcriptome profiles of single yeast cells at different ages, finding increased cell-to-cell transcriptional variability during aging. The single-cell transcriptome analysis also highlighted key biological processes or cellular components, including oxidation-reduction process, oxidative stress response (OSR), translation, ribosome biogenesis and mitochondrion that underlie aging in yeast. We uncovered a molecular marker of FIT3, indicating the early heterogeneity during aging in yeast. We also analyzed the regulation of transcription factors and further characterized the distinctive temporal regulation of the OSR by YAP1 and proteasome activity by RPN4 during aging in yeast. Overall, our data profoundly reveal early heterogeneity during aging in yeast and shed light on the aging dynamics at the single cell level.

Permissive aggregative group formation favors coexistence between cooperators and defectors in yeast

In Saccharomyces cerevisiae, the FLO1 gene encodes flocculins that lead to formation of multicellular flocs, that offer protection to the constituent cells. Flo1p was found to preferentially bind to fellow cooperators compared to defectors lacking FLO1 expression, enriching cooperators within the flocs. Given this dual function in cooperation and kin recognition, FLO1 has been termed a "green beard gene". Because of the heterophilic nature of the Flo1p bond however, we hypothesize that kin recognition is permissive and depends on the relative stability of the FLO1+/flo1- versus FLO1+/FLO1+ detachment force F. We combine single-cell measurements of adhesion, individual cell-based simulations of cluster formation, and in vitro flocculation to study the impact of relative bond stability on the evolutionary stability of cooperation. We identify a trade-off between both aspects of the green beard mechanism, with reduced relative bond stability leading to increased kin recognition at the expense of cooperative benefits. We show that the fitness of FLO1 cooperators decreases as their frequency in the population increases, arising from the observed permissive character (F+- = 0.5 F++) of the Flo1p bond. Considering the costs associated with FLO1 expression, this asymmetric selection often results in a stable coexistence between cooperators and defectors.

Changes in DNA double-strand break repair during aging correlate with an increase in genomic mutations

A double -strand break (DSB) is one of the most deleterious forms of DNA damage. In eukaryotic cells, two main repair pathways have evolved to repair DSBs, homologous recombination (HR) and non-homologous end-joining (NHEJ). HR is the predominant pathway of repair in the unicellular eukaryotic organism, S. cerevisiae. However, during replicative aging the relative use of HR and NHEJ shifts in favor of end-joining repair. By monitoring repair events in the HO-DSB system, we find that early in replicative aging there is a decrease in the association of long-range resection factors, Dna2-Sgs1 and Exo1 at the break site and a decrease in DNA resection. Subsequently, as aging progressed, the recovery of Ku70 at DSBs decreased and the break site associated with the nuclear pore complex at the nuclear periphery, which is the location where DSB repair occurs through alternative pathways that are more mutagenic. End-bridging remained intact as HR and NHEJ declined, but eventually it too became disrupted in cells at advanced replicative age. In all, our work provides insight into the molecular changes in DSB repair pathway during replicative aging. HR first declined, resulting in a transient increase in the NHEJ. However, with increased cellular divisions, Ku70 recovery at DSBs and NHEJ subsequently declined. In wild type cells of advanced replicative age, there was a high frequency of repair products with genomic deletions and microhomologies at the break junction, events not observed in young cells which repaired primarily by HR.

DetecDiv, a generalist deep-learning platform for automated cell division tracking and survival analysis

Automating the extraction of meaningful temporal information from sequences of microscopy images represents a major challenge to characterize dynamical biological processes. So far, strong limitations in the ability to quantitatively analyze single-cell trajectories have prevented large-scale investigations to assess the dynamics of entry into replicative senescence in yeast. Here, we have developed DetecDiv, a microfluidic-based image acquisition platform combined with deep learning-based software for high-throughput single-cell division tracking. We show that DetecDiv can automatically reconstruct cellular replicative lifespans with high accuracy and performs similarly with various imaging platforms and geometries of microfluidic traps. In addition, this methodology provides comprehensive temporal cellular metrics using time-series classification and image semantic segmentation. Last, we show that this method can be further applied to automatically quantify the dynamics of cellular adaptation and real-time cell survival upon exposure to environmental stress. Hence, this methodology provides an all-in-one toolbox for high-throughput phenotyping for cell cycle, stress response, and replicative lifespan assays.

A Primer Genetic Toolkit for Exploring Mitochondrial Biology and Disease Using Zebrafish

Mitochondria are a dynamic eukaryotic innovation that play diverse roles in biology and disease. The mitochondrial genome is remarkably conserved in all vertebrates, encoding the same 37-gene set and overall genomic structure, ranging from 16,596 base pairs (bp) in the teleost zebrafish (Danio rerio) to 16,569 bp in humans. Mitochondrial disorders are amongst the most prevalent inherited diseases, affecting roughly 1 in every 5000 individuals. Currently, few effective treatments exist for those with mitochondrial ailments, representing a major unmet patient need. Mitochondrial dysfunction is also a common component of a wide variety of other human illnesses, ranging from neurodegenerative disorders such as Huntington's disease and Parkinson's disease to autoimmune illnesses such as multiple sclerosis and rheumatoid arthritis. The electron transport chain (ETC) component of mitochondria is critical for mitochondrial biology and defects can lead to many mitochondrial disease symptoms. Here, we present a publicly available collection of genetic mutants created in highly conserved, nuclear-encoded mitochondrial genes in Danio rerio. The zebrafish system represents a potentially powerful new opportunity for the study of mitochondrial biology and disease due to the large number of orthologous genes shared with humans and the many advanced features of this model system, from genetics to imaging. This collection includes 15 mutant lines in 13 different genes created through locus-specific gene editing to induce frameshift or splice acceptor mutations, leading to predicted protein truncation during translation. Additionally, included are 11 lines created by the random insertion of the gene-breaking transposon (GBT) protein trap cassette. All these targeted mutant alleles truncate conserved domains of genes critical to the proper function of the ETC or genes that have been implicated in human mitochondrial disease. This collection is designed to accelerate the use of zebrafish to study many different aspects of mitochondrial function to widen our understanding of their role in biology and human disease.

Antagonistic effects of mitochondrial matrix and intermembrane space proteases on yeast aging

Background

In many organisms, aging is characterized by a loss of mitochondrial homeostasis. Multiple factors such as respiratory metabolism, mitochondrial fusion/fission, or mitophagy have been linked to cell longevity, but the exact impact of each one on the aging process is still unclear.

Results

Using the deletion mutant collection of the fission yeast Schizosaccharomyces pombe, we have developed a genome-wide screening for mutants with altered chronological lifespan. We have identified four mutants associated with proteolysis at the mitochondria that exhibit opposite effects on longevity. The analysis of the respiratory activity of these mutants revealed a positive correlation between increased respiration rate and prolonged lifespan. We also found that the phenotype of the long-lived protease mutants could not be explained by impaired mitochondrial fusion/fission activities, but it was dependent on mitophagy induction. The anti-aging role of mitophagy was supported by the effect of a mutant defective in degradation of mitochondria, which shortened lifespan of the long-lived mutants.

Conclusions

Our characterization of the mitochondrial protease mutants demonstrates that mitophagy sustains the lifespan extension of long-lived mutants displaying a higher respiration potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01352-w.

Multi-scale model suggests the trade-off between protein and ATP demand as a driver of metabolic changes during yeast replicative ageing

The accumulation of protein damage is one of the major drivers of replicative ageing, describing a cell's reduced ability to reproduce over time even under optimal conditions. Reactive oxygen and nitrogen species are precursors of protein damage and therefore tightly linked to ageing. At the same time, they are an inevitable by-product of the cell's metabolism. Cells are able to sense high levels of reactive oxygen and nitrogen species and can subsequently adapt their metabolism through gene regulation to slow down damage accumulation. However, the older or damaged a cell is the less flexibility it has to allocate enzymes across the metabolic network, forcing further adaptions in the metabolism. To investigate changes in the metabolism during replicative ageing, we developed an multi-scale mathematical model using budding yeast as a model organism. The model consists of three interconnected modules: a Boolean model of the signalling network, an enzyme-constrained flux balance model of the central carbon metabolism and a dynamic model of growth and protein damage accumulation with discrete cell divisions. The model can explain known features of replicative ageing, like average lifespan and increase in generation time during successive division, in yeast wildtype cells by a decreasing pool of functional enzymes and an increasing energy demand for maintenance. We further used the model to identify three consecutive metabolic phases, that a cell can undergo during its life, and their influence on the replicative potential, and proposed an intervention span for lifespan control.

The Nuclear Pore Complex: Birth, Life, and Death of a Cellular Behemoth

Nuclear pore complexes (NPCs) are the only transport channels that cross the nuclear envelope. Constructed from ~500-1000 nucleoporin proteins each, they are among the largest macromolecular assemblies in eukaryotic cells. Thanks to advances in structural analysis approaches, the construction principles and architecture of the NPC have recently been revealed at submolecular resolution. Although the overall structure and inventory of nucleoporins are conserved, NPCs exhibit significant compositional and functional plasticity even within single cells and surprising variability in their assembly pathways. Once assembled, NPCs remain seemingly unexchangeable in post-mitotic cells. There are a number of as yet unresolved questions about how the versatility of NPC assembly and composition is established, how cells monitor the functional state of NPCs or how they could be renewed. Here, we review current progress in our understanding of the key aspects of NPC architecture and lifecycle.

rDNA array length is a major determinant of replicative lifespan in budding yeast

The complex processes and interactions that regulate aging and determine lifespan are not fully defined for any organism. Here, taking advantage of recent technological advances in studying aging in budding yeast, we discovered a previously unappreciated relationship between the number of copies of the ribosomal RNA gene present in its chromosomal array and replicative lifespan (RLS). Specifically, the chromosomal ribosomal DNA (rDNA) copy number (rDNA CN) positively correlated with RLS and this interaction explained over 70% of variability in RLS among a series of wild-type strains. In strains with low rDNA CN, SIR2 expression was attenuated and extrachromosomal rDNA circle (ERC) accumulation was increased, leading to shorter lifespan. Suppressing ERC formation by deletion of FOB1 eliminated the relationship between rDNA CN and RLS. These data suggest that previously identified rDNA CN regulatory mechanisms limit lifespan. Importantly, the RLSs of reported lifespan-enhancing mutations were significantly impacted by rDNA CN, suggesting that changes in rDNA CN might explain the magnitude of some of those reported effects. We propose that because rDNA CN is modulated by environmental, genetic, and stochastic factors, considering rDNA CN is a prerequisite for accurate interpretation of lifespan data.

DNA circles promote yeast ageing in part through stimulating the reorganization of nuclear pore complexes

The nuclear pore complex (NPC) mediates nearly all exchanges between nucleus and cytoplasm, and in many species it changes composition as the organism ages. However, how these changes arise and whether they contribute themselves to ageing is poorly understood. We show that SAGA-dependent attachment of DNA circles to NPCs in replicatively ageing yeast cells causes NPCs to lose their nuclear basket and cytoplasmic complexes. These NPCs were not recognized as defective by the NPC quality control machinery (SINC) and not targeted by ESCRTs. They interacted normally or more effectively with protein import and export factors but specifically lost mRNA export factors. Acetylation of Nup60 drove the displacement of basket and cytoplasmic complexes from circle-bound NPCs. Mutations preventing this remodeling extended the replicative lifespan of the cells. Thus, our data suggest that the anchorage of accumulating circles locks NPCs in a specialized state and that this process is intrinsically linked to the mechanisms by which ERCs promote ageing.

Evaluation of In Situ Antiaging Activity in Saccharomyces cerevisiae BY611 Yeast Cells Treated with Polyalthia longifolia Leaf Methanolic Extract (PLME) Using Different Microscopic Approaches: A Morphology-Based Evaluation

Polyalthia longifolia is known for its anti-oxidative properties, which might contribute to the antiaging action. Hence, the current research was conducted to evaluate the antiaging activity of P. longifolia leaf methanolic extract (PLME) in a yeast model based on morphology using microscopic approaches. Saccharomyces cerevisiae BY611 strain yeast cells were treated with 1.00 mg/mL of PLME. The antiaging activity was assessed by determining the replicative lifespan, total lifespan, vacuole morphology by light microscopy, extra-morphology by scanning (SEM), and intra-morphology by transmission (TEM) electron microscopy. The findings demonstrated that PLME treatment significantly accelerated the replicative and total lifespan of the yeast cells. PLME treatment also delays the formation of large apoptotic-like type 3 yeast cell vacuoles. The untreated yeast cells demonstrated aging morphology via SEM analysis, such as shrinking, regional invaginations, and wrinkled cell surface. The TEM analysis revealed the quintessential aging intracellular morphology such as swollen, wrinkled, or damaged vacuole formation of the circular endoplasmic reticulum, a rupture in the nuclear membrane, fragmentation of the nucleus, and complete damaged cytoplasm. Decisively, the present study revealed the vital role of PLME in the induction of antiaging activity in a yeast model using three microscopic approaches—SEM, TEM, and bright-field light microscope.

Age-Dependent Decline of NAD+-Universal Truth or Confounded Consensus?

Nicotinamide adenine dinucleotide (NAD⁺) is an essential molecule involved in various metabolic reactions, acting as an electron donor in the electron transport chain and as a co-factor for NAD⁺-dependent enzymes. In the early 2000s, reports that NAD⁺ declines with aging introduced the notion that NAD⁺ metabolism is globally and progressively impaired with age. Since then, NAD⁺ became an attractive target for potential pharmacological therapies aiming to increase NAD⁺ levels to promote vitality and protect against age-related diseases. This review summarizes and discusses a collection of studies that report the levels of NAD⁺ with aging in different species (i.e., yeast, C. elegans, rat, mouse, monkey, and human), to determine whether the notion that overall NAD⁺ levels decrease with aging stands true. We find that, despite systematic claims of overall changes in NAD⁺ levels with aging, the evidence to support such claims is very limited and often restricted to a single tissue or cell type. This is particularly true in humans, where the development of NAD⁺ levels during aging is still poorly characterized. There is a need for much larger, preferably longitudinal, studies to assess how NAD⁺ levels develop with aging in various tissues. This will strengthen our conclusions on NAD metabolism during aging and should provide a foundation for better pharmacological targeting of relevant tissues.

Real-Time Monitoring of Dissection Events of Single Budding Yeast in a Microfluidic Cell-Culturing Device Integrated With Electrical Impedance Biosensor

Microfluidic devices in combination with fluorescent microscopy offer high-resolution and high-content platforms to study single-cell morphology, behavior and dynamic process in replicative aging of budding yeast, Saccharomyces cerevisiae. However, a huge mass of recorded images makes the data processing labor-intensive and time-consuming to determine yeast replicative lifespan (RLS), a primary criterion in yeast aging. To address this limitation and pursue label-free RLS assays, electrical impedance spectroscopy (EIS) that can be easily functionalized through microelectrodes in microfluidic devices, was introduced to monitor cell growth and division of budding yeast. Herein, a microfluidic device integrated with EIS biosensor was proposed to perform in-situ impedance measurement of yeast proliferation in single-cell resolution so as to identify the momentary events of daughter dissection from its mother. Single yeast cells were reliably immobilized at the bottleneck-like traps for continuous culturing, during which daughter cells were effectively detached from their mother cells by hydraulic shear forces. Time-lapse impedance measurement was performed every 2 min to monitor the cellular process including budding, division and dissection. By using the K-means clustering algorithm to analyze a self-defined parameter "Dissection Indicator," to our knowledge for the first time, the momentary event of a daughter removing from its mother cell was accurately extracted from EIS signals. Thus, the identification of daughter dissection events based on impedance sensing technology has been validated. With further development, this microfluidic device integrated with electrical impedance biosensor holds promising applications in high-throughput, real-time and label-free analysis of budding yeast aging and RLS.

Cell size is a determinant of stem cell potential during aging

Stem cells are remarkably small. Whether small size is important for stem cell function is unknown. We find that hematopoietic stem cells (HSCs) enlarge under conditions known to decrease stem cell function. This decreased fitness of large HSCs is due to reduced proliferation and was accompanied by altered metabolism. Preventing HSC enlargement or reducing large HSCs in size averts the loss of stem cell potential under conditions causing stem cell exhaustion. Last, we show that murine and human HSCs enlarge during aging. Preventing this age-dependent enlargement improves HSC function. We conclude that small cell size is important for stem cell function in vivo and propose that stem cell enlargement contributes to their functional decline during aging.

Long-term survival of Chlamydomonas reinhardtii during conditional senescence

Chlamydomonas reinhardtii undergoes conditional senescence when grown in batch culture due to nutrient limitation. Here, we explored plastid and photo-physiological adaptations in Chlamydomonas reinhardtii during a long-term ageing experiment by methodically sampling them over 22 weeks. Following exponential growth, Chlamydomonas entered an extended declining growth phase where cells continued to divide, although at a lower rate. Ultimately, this ongoing division was fueled by the recycling of macromolecules that was obvious in the rapidly declining protein and chlorophyll content in the cell during this phase. This process was sufficient to maintain a high level of cell viability as the culture entered stationary phase. Beyond that the cell viability starts to plummet. During the turnover of macromolecules after exponential growth that saw RuBisCO levels drop, the LHCII antenna was relatively stable. This, along with the upregulation of the light stress-related proteins (LHCSR), contributes to an efficient energy dissipation mechanism to protect the ageing cells from photooxidative stress during the senescence process. Ultimately, viability dropped to about 7% at 22 weeks in a batch culture. We anticipate that this research will help further understand the various acclimation strategies carried out by Chlamydomonas to maximize survival under conditional senescence.

Mechanism of Growth Regulation of Yeast Involving Hydrogen Sulfide From S-Propargyl-Cysteine Catalyzed by Cystathionine-γ-Lyase

Pathogenic fungi are recognized as a progressive threat to humans, particularly those with the immunocompromised condition. The growth of fungi is controlled by several factors, one of which is signaling molecules, such as hydrogen sulfide (H₂S), which was traditionally regarded as a toxic gas without physiological function. However, recent studies have revealed that H₂S is produced enzymatically and endogenously in several species, where it serves as a gaseous signaling molecule performing a variety of critical biological functions. However, the influence of this endogenous H₂S on the biological activities occurring within the pathogenic fungi, such as transcriptomic and phenotypic alternations, has not been elucidated so far. Therefore, the present study was aimed to decipher this concern by utilizing S-propargyl-cysteine (SPRC) as a novel and stable donor of H₂S and Saccharomyces cerevisiae as a fungal model. The results revealed that the yeast could produce H₂S by catabolizing SPRC, which facilitated the growth of the yeast cells. This implies that the additional intracellularly generated H₂S is generated primarily from the enhanced sulfur-amino-acid-biosynthesis pathways and serves to increase the growth rate of the yeast, and presumably the growth of the other fungi as well. In addition, by deciphering the implicated pathways and analyzing the in vitro enzymatic activities, cystathionine-γ-lyase (CYS3) was identified as the enzyme responsible for catabolizing SPRC into H₂S in the yeast, which suggested that cystathionine-γ-lyase might play a significant role in the regulation of H₂S-related transcriptomic and phenotypic alterations occurring in yeast. These findings provide important information regarding the mechanism underlying the influence of the gaseous signaling molecules such as H₂S on fungal growth. In addition, the findings provide a better insight to the in vivo metabolism of H₂S-related drugs, which would be useful for the future development of anti-fungal drugs.

Understanding the Impact of Industrial Stress Conditions on Replicative Aging in Saccharomyces cerevisiae

In yeast, aging is widely understood as the decline of physiological function and the decreasing ability to adapt to environmental changes. Saccharomyces cerevisiae has become an important model organism for the investigation of these processes. Yeast is used in industrial processes (beer and wine production), and several stress conditions can influence its intracellular aging processes. The aim of this review is to summarize the current knowledge on applied stress conditions, such as osmotic pressure, primary metabolites (e.g., ethanol), low pH, oxidative stress, heat on aging indicators, age-related physiological changes, and yeast longevity. There is clear evidence that yeast cells are exposed to many stressors influencing viability and vitality, leading to an age-related shift in age distribution. Currently, there is a lack of rapid, non-invasive methods allowing the investigation of aspects of yeast aging in real time on a single-cell basis using the high-throughput approach. Methods such as micromanipulation, centrifugal elutriator, or biotinylation do not provide real-time information on age distributions in industrial processes. In contrast, innovative approaches, such as non-invasive fluorescence coupled flow cytometry intended for high-throughput measurements, could be promising for determining the replicative age of yeast cells in fermentation and its impact on industrial stress conditions.

Seeking Insights into Aging Through Yeast Mitochondrial Electrophysiology

During aging, mitochondrial membrane potential, a key indicator for bioenergetics of cells, depolarizes in a wide range of species-from yeasts, plants to animals. In humans, the decline of mitochondrial activities can impact the high-energy-consuming organs, such as the brain and heart, and increase the risks of age-linked diseases. Intriguingly, a mild depolarization of mitochondria has lifespan-extending effects, suggesting an important role played by bioelectricity during aging. However, the underpinning biophysical mechanism is not very well understood due in part to the difficulties associated with a multiscale process. Budding yeast Saccharomyces cerevisiae could provide a model system to bridge this knowledge gap and provide insights into aging. In this perspective, we overview recent studies on the yeast mitochondrial membrane electrophysiology and aging and call for more electrochemical and biophysical studies on aging.

Difference between the cell wall roughnesses of mothers and daughters of Saccharomyces cerevisiae subjected to high pressure stress

High hydrostatic pressure (HHP) stress generates cellular responses similar to those to other stresses that yeasts endure in fermentation tanks. Structural and spatial compaction of molecules, as well as weakening and stretching of plasma membranes and cell walls, are often observed and have a significant influence on the fermentative process. Atomic force microscopy (AFM) yields accurate data on the morphological characteristics of yeast cell walls, providing important insights for the development of more productive yeast strains. Saccharomyces cerevisiae cell wall assessment using AFM in the intermittent contact reading mode using a silicon cantilever, before and after application of a pressure of 100 MPa for 30 min, demonstrated that mother and daughter cells have different responses. Daughter cells were more sensitive to the effects of HHP, presenting lower average Ra (arithmetic roughness), Rz (ten-point average roughness), and Rq (root-mean-square roughness) after exposure to high pressure. Better adaptation to stress in mother cells leads to higher cell wall resistance and, therefore, to better protection.

Revealing the antiaging effects of cereal- and food oil-derived active substances by a Caenorhabditis elegans model

Cereal grains and oils contain various functional ingredients, such as amino acids, peptides, polyphenols, dietary fiber, linoleic acid, and natural pigments. Their biological activities are of great significance. Benefiting from its robust genetic function and simple cultivation, Caenorhabditis elegans, as one of the most important model organisms has been widely used to screen antiaging substances and investigate the underlying molecular mechanisms. In this paper, the recent advances in the use of C. elegans in antiaging research into active substances from cereals and oils will be assessed, and their potential signal transduction mechanisms will be systematically reviewed. This research aims to provide a theoretical reference for the use of active substances from cereals and oils to prevent and delay aging and aging-associated diseases.

Stress response capacity analysis during aging and possible new insights into aging studies

The causes and consequences of aging have always been a concern. In recent studies, changes in the stress response capacity of cells during aging were quantitatively analyzed. It was found that aging was accompanied by a decline in response capacity. When the response capacity decreased to a critical value, which we assumed was the internal noise level, the cell soon died. To survive, the response capacity should be, at minimum, sufficiently strong to resist intracellular noise. Here, we discuss the role of stress response capacity in aging and conjecture that lifespan might be extended by enhancing stress response capacity.

Long-Living Budding Yeast Cell Subpopulation Induced by Ethanol/Acetate and Respiration

Budding yeast generate heterogeneous cells that can be separated into two distinctive cell types: short-living low-density and long-living high-density (HD) cells by density gradient centrifugation. We found that ethanol and acetate induce formation of HD cells, and mitochondrial respiration is required. From their transcriptomes and metabolomes, we found upregulated differentially expressed genes in HD cells involved in the RGT2/RGT1 glucose sensing pathway and its downstream genes encoding hexose transporters. For HD cells, we determined an abundance of various carbon sources including glucose, lactate, pyruvate, trehalose, mannitol, mannose, and galactose. Other upregulated differentially expressed genes in HD cells were involved in the TORC1-SCH9 signaling pathway and its downstream genes involved in cytoplasmic translation. We also measured an abundance of free amino acids in HD cells including valine, proline, isoleucine, and glutamine. These characteristics of the HD cell transcriptome and metabolome may be important conditions for maintaining a long-living phenotype.

Asymmetric Transcription Factor Partitioning During Yeast Cell Division Requires the FACT Chromatin Remodeler and Cell Cycle Progression

The polarized partitioning of proteins in cells underlies asymmetric cell division, which is an important driver of development and cellular diversity. The budding yeast Saccharomyces cerevisiae divides asymmetrically, like many other cells, to generate two distinct progeny cells. A well-known example of an asymmetric protein is the transcription factor Ace2, which localizes specifically to the daughter nucleus, where it drives a daughter-specific transcriptional network. We screened a collection of essential genes to analyze the effects of core cellular processes in asymmetric cell division based on Ace2 localization. This screen identified mutations that affect progression through the cell cycle, suggesting that cell cycle delay is sufficient to disrupt Ace2 asymmetry. To test this model, we blocked cells from progressing through mitosis and found that prolonged metaphase delay is sufficient to disrupt Ace2 asymmetry after release, and that Ace2 asymmetry is restored after cytokinesis. We also demonstrate that members of the evolutionarily conserved facilitates chromatin transcription (FACT) chromatin-reorganizing complex are required for both asymmetric and cell cycle-regulated localization of Ace2, and for localization of the RAM network components.

Excessive rDNA Transcription Drives the Disruption in Nuclear Homeostasis during Entry into Senescence in Budding Yeast

Budding yeast cells undergo a limited number of divisions before they enter senescence and die. Despite recent mechanistic advances, whether and how molecular events are temporally and causally linked during the transition to senescence remain elusive. Here, using real-time observation of the accumulation of extrachromosomal rDNA circles (ERCs) in single cells, we provide evidence that ERCs build up rapidly with exponential kinetics well before any physiological decline. We then show that ERCs fuel a massive increase in ribosomal RNA (rRNA) levels in the nucleolus, which do not mature into functional ribosomes. This breakdown in nucleolar coordination is followed by a loss of nuclear homeostasis, thus defining a chronology of causally related events leading to cell death. A computational analysis supports a model in which a series of age-independent processes lead to an age-dependent increase in cell mortality, hence explaining the emergence of aging in budding yeast.

Age-dependent decline in stress response capacity revealed by proteins dynamics analysis

The aging process is regarded as the progressive loss of physiological integrity, leading to impaired biological functions and the increased vulnerability to death. Among various biological functions, stress response capacity enables cells to alter gene expression patterns and survive when facing internal and external stresses. Here, we explored changes in stress response capacity during the replicative aging of Saccharomyces cerevisiae. To this end, we used a high-throughput microfluidic device to deliver intermittent pulses of osmotic stress and tracked the dynamic changes in the production of downstream stress-responsive proteins, in a large number of individual aging cells. Cells showed a gradual decline in stress response capacity of these osmotic-related downstream proteins during the aging process after the first 5 generations. Among the downstream stress-responsive genes and unrelated genes tested, the residual level of response capacity of Trehalose-6-Phosphate Synthase (TPS2) showed the best correlation with the cell remaining lifespan. By monitor dynamics of the upstream transcription factors and mRNA of Tps2, it was suggested that the decline in downstream stress response capacity was caused by the decline of translational rate of these proteins during aging.

Changes in Metabolism and Proteostasis Drive Aging Phenotype in Aplysia californica Sensory Neurons

Aging is associated with cognitive declines that originate in impairments of function in the neurons that make up the nervous system. The marine mollusk Aplysia californica (Aplysia) is a premier model for the nervous system uniquely suited to investigation of neuronal aging due to uniquely identifiable neurons and molecular techniques available in this model. This study describes the molecular processes associated with aging in two populations of sensory neurons in Aplysia by applying RNA sequencing technology across the aging process (age 6-12 months). Differentially expressed genes clustered into four to five coherent expression patterns across the aging time series in the two neuron populations. Enrichment analysis of functional annotations in these neuron clusters revealed decreased expression of pathways involved in energy metabolism and neuronal signaling, suggesting that metabolic and signaling pathways are intertwined. Furthermore, increased expression of pathways involved in protein processing and translation suggests that proteostatic stress also occurs in aging. Temporal overlap of enrichment for energy metabolism, proteostasis, and neuronal function suggests that cognitive impairments observed in advanced age result from the ramifications of broad declines in energy metabolism.

Isolation of Aged Yeast Cells Using Biotin-Streptavidin Affinity Purification

Yeast (Saccharomyces cerevisiae) has been used as one of the main model systems for studying molecular mechanisms underlying cellular aging. A major technical challenge in studying aging in yeast is the isolation of aged cells from exponentially growing cell cultures, since aged cells in such cultures are rare. Several methods for isolating aged cells have been developed to achieve this. Here, we describe a biotin-streptavidin affinity purification protocol for isolating aged yeast cells. It consists of three main steps: biotinylation of yeast cells, culturing cells to the desired age, and harvesting the aged cells using streptavidin-coated magnetic microbeads. The isolated aged cells can be used for microscopy, biochemistry, or molecular biology analysis.

Linkage between Carbon Metabolism, Redox Status and Cellular Physiology in the Yeast Saccharomyces cerevisiae Devoid of SOD1 or SOD2 Gene

Saccharomyces cerevisiae yeast cells may generate energy both by fermentation and aerobic respiration, which are dependent on the type and availability of carbon sources. Cells adapt to changes in nutrient availability, which entails the specific costs and benefits of different types of metabolism but also may cause alteration in redox homeostasis, both by changes in reactive oxygen species (ROS) and in cellular reductant molecules contents. In this study, yeast cells devoid of the SOD1 or SOD2 gene and fermentative or respiratory conditions were used to unravel the connection between the type of metabolism and redox status of cells and also how this affects selected parameters of cellular physiology. The performed analysis provides an argument that the source of ROS depends on the type of metabolism and non-mitochondrial sources are an important pool of ROS in yeast cells, especially under fermentative metabolism. There is a strict interconnection between carbon metabolism and redox status, which in turn has an influence on the physiological efficiency of the cells. Furthermore, pyridine nucleotide cofactors play an important role in these relationships.

Proteostatic stress as a nodal hallmark of replicative aging

Aging is characterized by the progressive decline of physiology at the cell, tissue and organism level, leading to an increased risk of mortality. Proteotoxic stress, mitochondrial dysfunction and genomic instability are considered major universal drivers of cell aging, and accumulating evidence establishes clear biunivocal relationships among these key hallmarks. In this regard, the finite lifespan of the budding yeast, together with the extensive armamentarium of available analytical tools, has made this single cell eukaryote a key model to study aging at molecular and cellular levels. Here we review the current data that link proteostasis to cell cycle progression in the budding yeast, focusing on senescence as an inherent phenotype displayed by aged cells. Recent advances in high-throughput systems to study yeast mother cells while they replicate are providing crucial information on aging-related processes and their temporal interdependencies at a systems level. In our view, the available data point to the existence of multiple feedback mechanisms among the major causal factors of aging, which would converge into the loss of proteostasis as a nodal driver of cell senescence and death.

Discovery of fifteen new geroprotective plant extracts and identification of cellular processes they affect to prolong the chronological lifespan of budding yeast

In a quest for previously unknown geroprotective natural chemicals, we used a robust cell viability assay to search for commercially available plant extracts that can substantially prolong the chronological lifespan of budding yeast. Many of these plant extracts have been used in traditional Chinese and other herbal medicines or the Mediterranean and other customary diets. Our search led to a discovery of fifteen plant extracts that significantly extend the longevity of chronologically aging yeast not limited in calorie supply. We show that each of these longevity-extending plant extracts is a geroprotector that decreases the rate of yeast chronological aging and promotes a hormetic stress response. We also show that each of the fifteen geroprotective plant extracts mimics the longevity-extending, stress-protecting, metabolic and physiological effects of a caloric restriction diet but if added to yeast cultured under non-caloric restriction conditions. We provide evidence that the fifteen geroprotective plant extracts exhibit partially overlapping effects on a distinct set of longevity-defining cellular processes. These effects include a rise in coupled mitochondrial respiration, an altered age-related chronology of changes in reactive oxygen species abundance, protection of cellular macromolecules from oxidative damage, and an age-related increase in the resistance to long-term oxidative and thermal stresses.

Asymmetric inheritance of mitochondria in yeast

Mitochondria are essential organelles of virtually all eukaryotic organisms. As they cannot be made de novo, they have to be inherited during cell division. In this review, we provide an overview on mitochondrial inheritance in Saccharomyces cerevisiae, a powerful model organism to study asymmetric cell division. Several processes have to be coordinated during mitochondrial inheritance: mitochondrial transport along the actin cytoskeleton into the emerging bud is powered by a myosin motor protein; cell cortex anchors retain a critical fraction of mitochondria in the mother cell and bud to ensure proper partitioning; and the quantity of mitochondria inherited by the bud is controlled during cell cycle progression. Asymmetric division of yeast cells produces rejuvenated daughter cells and aging mother cells that die after a finite number of cell divisions. We highlight the critical role of mitochondria in this process and discuss how asymmetric mitochondrial partitioning and cellular aging are connected.

A guiding torch at the poles: the multiple roles of spindle microtubule-organizing centers during cell division

The spindle constitutes the cellular machinery that enables the segregation of the chromosomes during eukaryotic cell division. The microtubules that form this fascinating and complex genome distribution system emanate from specialized structures located at both its poles and known as microtubule-organizing centers (MTOCs). Beyond their structural function, the spindle MTOCs play fundamental roles in cell cycle control, the activation and functionality of the mitotic checkpoints and during cellular aging. This review highlights the pivotal importance of spindle-associated MTOCs in multiple cellular processes and their central role as key regulatory hubs where diverse intracellular signals are integrated and coordinated to ensure the successful completion of cell division and the maintenance of the replicative lifespan.