The Fourth Annual Symposium of the Midwest Aging Consortium.

The Midwest Aging Consortium (MAC) has emerged as a critical collaborative initiative aimed at advancing our understanding of aging and developing strategies to combat the rising prevalence of age-related diseases. Founded in 2019, MAC brings together researchers from various disciplines and institutions across the Midwestern United States to foster interdisciplinary geroscience research. This report summarizes the highlights of the Fourth Annual Symposium of MAC, which was held at Iowa State University in May 2023.

Maternal age effects on offspring lifespan and reproduction vary within a species.

Across diverse taxa, offspring from older mothers have decreased lifespan and fitness. Little is known about the extent to which maternal age effects vary among genotypes for a given species, however, except for studies of a few arthropod species. To investigate the presence and degree of intraspecific variability in maternal age effects, we compared lifespan, reproductive schedule, and lifetime reproductive output of offspring produced by young, middle-aged, and old mothers in four strains of rotifers in the species complex.

A free and user-friendly software protocol for the quantification of microfauna swimming behavior.

Characterizing swimming behavior can provide a holistic assessment of the health, physiology and ecology of microfaunal species when done in conjunction with measuring other biological parameters. However, tracking and quantifying microfauna swimming behavior using existing automated tools is often difficult due to the animals' small size or transparency, or because of the high cost, expertise, or labor needed for the analysis. To address these issues, we created a cost-effective, user-friendly protocol for behavior analysis that employs the free software packages HitFilm and ToxTrac along with the R package 'trajr' and used the method to quantify the behavior of rotifers.

Highly efficient CRISPR-mediated gene editing in a rotifer.

Rotifers have been studied in the laboratory and field for over 100 years in investigations of microevolution, ecological dynamics, and ecotoxicology. In recent years, rotifers have emerged as a model system for modern studies of the molecular mechanisms of genome evolution, development, DNA repair, aging, life history strategy, and desiccation tolerance. However, a lack of gene editing tools and transgenic strains has limited the ability to link genotype to phenotype and dissect molecular mechanisms.

SAG-RAD: A Method for Single-Cell Population Genomics of Unicellular Eukaryotes.

Sequencing of reduced representation libraries enables genotyping of many individuals for population genomic studies. However, high amounts of DNA are required, and the method cannot be applied directly on single cells, preventing its use on most microbes. We developed and implemented the analysis of single amplified genomes followed by restriction-site-associated DNA sequencing to bypass labor-intensive culturing and to avoid culturing bias in population genomic studies of unicellular eukaryotes.

Maternal age effects on offspring lifespan and reproduction vary within a species.

Across diverse taxa, offspring from older mothers have decreased lifespan and fitness. Little is known about whether such maternal age effects vary among genotypes for a given species, however. We compared maternal age effects among four strains of rotifers in the species complex.

The Contributions of Maternal Age Heterogeneity to Variance in Lifetime Reproductive Output.

AbstractVariance among individuals in fitness components reflects both genuine heterogeneity between individuals and stochasticity in events experienced along the life cycle. Maternal age represents a form of heterogeneity that affects both the mean and the variance of lifetime reproductive output (LRO). Here, we quantify the relative contribution of maternal age heterogeneity to the variance in LRO using individual-level laboratory data on the rotifer to parameterize a multistate age × maternal age matrix model.

Sex-specific aging in animals: Perspective and future directions.

Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age-associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer-lived females, species where males live longer, and species lacking sex differences in lifespan.

Brachionus rotifers as a model for investigating dietary and metabolic regulators of aging.

Because every species has unique attributes relevant to understanding specific aspects of aging, using a diversity of study systems and a comparative biology approach for aging research has the potential to lead to novel discoveries applicable to human health. Monogonont rotifers, a standard model for studies of aquatic ecology, evolutionary biology, and ecotoxicology, have also been used to study lifespan and healthspan for nearly a century. However, because much of this work has been published in the ecology and evolutionary biology literature, it may not be known to the biomedical research community.

A demographic and evolutionary analysis of maternal effect senescence.

Maternal effect senescence-a decline in offspring survival or fertility with maternal age-has been demonstrated in many taxa, including humans. Despite decades of phenotypic studies, questions remain about how maternal effect senescence impacts evolutionary fitness. To understand the influence of maternal effect senescence on population dynamics, fitness, and selection, we developed matrix population models in which individuals are jointly classified by age and maternal age.

Transglutaminase Activity Determines Nuclear Localization of Serotonin Immunoreactivity in the Early Embryos of Invertebrates and Vertebrates.

Serotonin (5-HT) is a key player in many physiological processes in both the adult organism and developing embryo. One of the mechanisms for 5-HT-mediated effects is covalent binding of 5-HT to the target proteins catalyzed by transglutaminases (serotonylation). Despite the implication in a variety of physiological processes, the involvement of serotonylation in embryonic development remains unclear.

Maternal age alters offspring lifespan, fitness, and lifespan extension under caloric restriction.

Maternal age has a negative effect on offspring lifespan in a range of taxa and is hypothesized to influence the evolution of aging. However, the mechanisms of maternal age effects are unknown, and it remains unclear if maternal age alters offspring response to therapeutic interventions to aging. Here, we evaluate maternal age effects on offspring lifespan, reproduction, and the response to caloric restriction, and investigate maternal investment as a source of maternal age effects using the rotifer, Brachionus manjavacas, an aquatic invertebrate.

Congeneric variability in lifespan extension and onset of senescence suggest active regulation of aging in response to low temperature.

Lifespan extension under low temperature is well conserved across both endothermic and exothermic taxa, but the mechanism underlying this change in aging is poorly understood. Low temperature is thought to decrease metabolic rate, thus slowing the accumulation of cellular damage from reactive oxygen species, although recent evidence suggests involvement of specific cold-sensing biochemical pathways. We tested the effect of low temperature on aging in 11 strains of Brachionus rotifers, with the hypothesis that if the mechanism of lifespan extension is purely thermodynamic, all strains should have a similar increase in lifespan.

Genome-wide transcriptomics of aging in the rotifer Brachionus manjavacas, an emerging model system.

Background: Understanding gene expression changes over lifespan in diverse animal species will lead to insights to conserved processes in the biology of aging and allow development of interventions to improve health. Rotifers are small aquatic invertebrates that have been used in aging studies for nearly 100 years and are now re-emerging as a modern model system. To provide a baseline to evaluate genetic responses to interventions that change health throughout lifespan and a framework for new hypotheses about the molecular genetic mechanisms of aging, we examined the transcriptome of an asexual female lineage of the rotifer Brachionus manjavacas at five life stages: eggs, neonates, and early-, late-, and post-reproductive adults.

Measurement of Survival Time in Brachionus Rotifers: Synchronization of Maternal Conditions.

Rotifers are microscopic cosmopolitan zooplankton used as models in ecotoxicological and aging studies due to their several advantages such as short lifespan, ease of culture, and parthenogenesis that enables clonal culture. However, caution is required when measuring their survival time as it is affected by maternal age and maternal feeding conditions. Here we provide a protocol for powerful and reproducible measurement of the survival time in Brachionus rotifers following a careful synchronization of culture conditions over several generations.

Rotifers as experimental tools for investigating aging.

Comparative biogerontology has much to contribute to the study of aging. A broad range of aging rates has evolved to meet environmental challenges, and understanding these adaptations can produce valuable insights into aging. The supra Phylum Lophotrochozoa is particularly understudied and has several groups that have intriguing patterns of aging.

Maternal caloric restriction partially rescues the deleterious effects of advanced maternal age on offspring.

While many studies have focused on the detrimental effects of advanced maternal age and harmful prenatal environments on progeny, little is known about the role of beneficial non-Mendelian maternal inheritance on aging. Here, we report the effects of maternal age and maternal caloric restriction (CR) on the life span and health span of offspring for a clonal culture of the monogonont rotifer Brachionus manjavacas. Mothers on regimens of chronic CR (CCR) or intermittent fasting (IF) had increased life span compared with mothers fed ad libitum (AL).

Patterns of intraspecific variability in the response to caloric restriction.

Caloric restriction (CR) is cited as the most robust means of increasing lifespan across a range of taxa, yet there is a high degree of variability in the response to CR, both within and between species. To examine the intraspecific evolutionary conservation of lifespan extension by CR, we tested the effects of chronic caloric restriction (CCR) at multiple food levels and of intermittent fasting (IF) in twelve isolates from the Brachionus plicatilis species complex of monogonont rotifers. While CCR generally increased or did not change lifespan and total fecundity, IF caused increased, unchanged, or decreased lifespan, depending upon the isolate, and decreased total fecundity in all but one isolate.

Life-span extension by caloric restriction is determined by type and level of food reduction and by reproductive mode in Brachionus manjavacas (Rotifera).

We measured life span and fecundity of three reproductive modes in a clone of the monogonont rotifer Brachionus manjavacas subjected to chronic caloric restriction (CCR) over a range of food concentrations or to intermittent fasting (IF). IF increased life span 50%-70% for all three modes, whereas CCR increased life span of asexual females derived from sexually or asexually produced eggs, but not that of sexual females. The main effect of CR on both asexual modes was to delay death at young ages, rather than to prevent death at middle ages or to greatly extend maximum life span; in contrast CR in sexual females greatly increased the life span of a few long-lived individuals.

The mate recognition protein gene mediates reproductive isolation and speciation in the Brachionus plicatilis cryptic species complex.

Background: Chemically mediated prezygotic barriers to reproduction likely play an important role in speciation. In facultatively sexual monogonont rotifers from the Brachionus plicatilis cryptic species complex, mate recognition of females by males is mediated by the Mate Recognition Protein (MRP), a globular glycoprotein on the surface of females, encoded by the mmr-b gene family. In this study, we sequenced mmr-b copies from 27 isolates representing 11 phylotypes of the B.

Genetic determinants of mate recognition in Brachionus manjavacas (Rotifera).

Background: Mate choice is of central importance to most animals, influencing population structure, speciation, and ultimately the survival of a species. Mating behavior of male brachionid rotifers is triggered by the product of a chemosensory gene, a glycoprotein on the body surface of females called the mate recognition pheromone. The mate recognition pheromone has been biochemically characterized, but little was known about the gene(s).

Sexual and asexual processes in Protoperidinium steidingerae Balech (Dinophyceae), with observations on life-history stages of Protoperidinium depressum (Bailey) Balech (Dinophyceae).

A suite of morphological, histological, and molecular techniques was used to reveal for the first time division, sexuality, mandatory dormancy period of hypnozygotes, and identity of life-history stages of any Protoperidinium spp. In both Protoperidinium steidingerae and Protoperidinium depressum, asexual division occurred by eleutheroschisis within a temporary cyst, yielding two daughter cells. Daughter cells were initially round and one-half to two-thirds the size of parent cells then rapidly increased in size, forming horns before separating.