Gribble, Kristin E.
Dr. Gribble is a molecular biologist broadly interested in the evolution, ecology and life history of marine and freshwater plankton. She combines her training in biological oceanography, evolution, and molecular biology to investigate how environment and genetics influence the phenotypic plasticity of life history strategy and morphology to allow adaptation to changes in environmental conditions and to determine evolutionary fitness. By understanding the outcomes induced by specific environmental conditions, the molecular genetic bases of phenotypic changes, and the evolutionary conservation of plasticity, Dr. Gribble’s research enables predictions about the results of changing environmental conditions at scales ranging from the individual to the ecosystem. Dr. Gribble has employed two main study systems in her work: marine dinoflagellates (single cell aquatic protists) and rotifers (microscopic invertebrates found in freshwater and estuarine ecosystems). She described the relationship between the molecular phylogeny and morphological taxonomy of an important and widespread genus of heterotrophic dinoflagellates, Protoperidinium, and described the group’s biogeography off the western coast of Ireland. Dr. Gribble provided the first description of the life history, including sexual and asexual reproduction, of two species of Protoperidinium. Recently, Dr. Gribble has collaborated with Dr. David B. Mark Welch at the Marine Biological Laboratory on studies of evolution, life history, and aging using monogonont rotifers. With a short lifespan, ease of culture, a large foundation of ecological data, and a suite of genetic tools, rotifers are a tractable system for investigating many basic biological questions, including the evolution of mate recognition and speciation, and as a model system to study the mechanisms and evolution of the biology of aging.
Biology of Aging: Mechanisms and evolutionary conservation of therapeutic interventions
As monogonont rotifers have not undergone the substantial genome reduction of other invertebrate model species, they provide a robust and viable system in which to investigate questions relevant to human health. Dr. Mark Welch and Dr. Gribble are using rotifers to study the genetic mechanisms of therapies that increase lifespan and improve health during aging, and to determinethe degree of conservation of beneficial responses to therapies. Severely limiting food intake, also known as caloric restriction (CR), is one of the most reliable means of extending lifespan in a variety of animals, yet the evolutionary origins and genetic mechanisms behind the response to CR are poorly understood. Dr. Gribble has investigated lifespan and fecundity changes in response to a variety of levels of CR among 12 strains of the rotifer Brachionus plicatilis isolated from different environments and found that the level of lifespan extension was different between sexual and asexual individuals of the same species. Interestingly, the degree of lifespan extension under CR was inversely correlated with lifespan under food-replete conditions. Differences in reproduction under varied CR regimens, even when lifespan extension was similar, suggested that different types of CR extend lifespan through diverse genetic mechanisms. Ongoing projects include analysis of differential gene expression over the rotifer life cycle and comparing gene expression in isolates with different responses to food limitation to identify genes involved in lifespan extension, using RNA-Seq.
Protoperidinium steidingerae isolated from the Atlantic Ocean, south of Martha’s Vineyard. Protoperidinium are single cell, heterotrophic dinoflagellates with complex life cycles; they occupy a unique position in the trophic dynamics of the plankton in marine systems, as they consume phytoplankton larger than themselves. Photo credit: Kristin Gribble.
Brachionus manjavacas female carrying a single egg. Brachionus rotifers are approximately 500 µm long, are composed of 1000 cells, and have defined digestive, nervous, reproductive and muscular systems. Monognont rotifers like Brachionus generally reproduce asexually, with occasional bouts of sexual reproduction. They play a significant role in freshwater and marine ecosystems as consumers of phytoplankton and bacteria and are emerging as an important model system for studying questions of evolution and the biology of aging. Photo credit: Kristin Gribble.
Biology of Aging: Maternal effects
Phenotypic plasticity may occur not only in an individual, but also across generations. Transgenerational phenotypic plasticity, known as a “maternal effect,” occurs when the maternal response to the environment causes a change in offspring phenotype without a change in the genome. While many studies have focused on the detrimental effects on progeny of advanced maternal age and harmful prenatal environments, little is known about the role of beneficial maternal inheritance on aging. Dr. Gribble investigated the effects of maternal age and maternal CR on the lifespan and healthspan of Brachionus manjavacas offspring. With increasing maternal age, lifespan and fecundity of female offspring of fully fed mothers decreased significantly. Maternal CR partially rescued these effects, increasing the mean lifespan and fecundity of female offspring but not of male offspring. Understanding the influence and mechanisms of maternal effects on aging will provide fertile ground for future research and for development of therapies to improve human health during aging.