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Stephen C Stearns

Publications and source records attributed to Stephen C Stearns.

7 recordsLinked to original sources
PubMed2003

The naturalist in a world of genomics.

Functional genomics provides new opportunities to address issues of fundamental interest in evolutionary biology and suggests many new research directions that are ripe for evolutionary investigation. New types of data, and the ability to study biological processes from a whole genome perspective, are likely to have a profound impact on evolutionary biology and ecology. To illustrate, we discuss how genomewide gene expression studies can be used to reformulate questions about trade-offs and pleiotropy. We then touch on some of the new research opportunities that the application of functional genomics affords to evolutionary biologists. We end with some brief notes about how evolutionary biology and comparative approaches will probably have an impact on functional genomics.

Animals↗
PubMed2002

Genome-wide transcript profiles in aging and calorically restricted Drosophila melanogaster.

BACKGROUND: We characterized RNA transcript levels for the whole Drosophila genome during normal aging. We compared age-dependent profiles from animals aged under full-nutrient conditions with profiles obtained from animals maintained on a low-calorie medium to determine if caloric restriction slows the aging process. Specific biological functions impacted by caloric restriction were identified using the Gene Ontology annotation. We used the global patterns of expression profiles to test if particular genomic regions contribute differentially to changes in transcript profiles with age and if global disregulation of gene expression occurs during aging. RESULTS: Whole-genome transcript profiles contained a statistically powerful genetic signature of normal aging. Nearly 23% of the genome changed in transcript representation with age. Caloric restriction was accompanied by a slowing of the progression of normal, age-related changes in transcript levels. Many genes, including those associated with stress response and oogenesis, showed age-dependent transcript representation. Caloric restriction resulted in the downregulation of genes primarily involved in cell growth, metabolism, and reproduction. We found no evidence that age-dependent changes in transcription level were confined to genes localized to specific regions of the genome and found no support for widespread disregulation of gene expression with age. CONCLUSIONS: Aging is characterized by highly dynamic changes in the expression of many genes, which provides a powerful molecular description of the normal aging process. Caloric restriction extends life span by slowing down the rate of normal aging. Transcription levels of genes from a wide variety of biological functions and processes are impacted by age and dietary conditions.

Aging↗
PubMedDate not supplied

Issues in evolutionary medicine.

This paper illustrates the utility of applying evolutionary thought to medical issues with three examples: selection arenas, aging, and tradeoffs. First, the human female reproductive tract functions as a selection arena at two levels: in the ovaries, where atresia reduces the number of oocytes by more than 99.99% before any are ovulated, and in the uterus, where early embryos homozygous for immune genes are spontaneously aborted. These selective filters early in life have implications both for eugenics and for the anti-abortion movement. Second, the evolutionary theory of aging predicts that intrinsic mortality should reflect extrinsic mortality: if life for adults is risky, then it does not pay to invest in maintenance at the expense of reproduction. This idea is well confirmed, at least in populations where density effects are not important. While only organisms that reproduce asymmetrically should age, even bacteria reproduce asymmetrically, and they do age, suggesting that all organisms reproduce asymmetrically and therefore age. Third, tradeoffs are central to theories of phenotypic design, but the mechanisms that cause them remain obscure. A method is suggested to get at the mechanisms of tradeoffs by examining conflicts among functions over gene expression. It could be applied in humans to the tradeoff between reproductive performance and disease resistance.

Aging↗