Project description:The acute phase response (APR) is the first line of defense of the vertebrate immune system against pathogens. Mounting an immune response is believed to be energetically costly but direct measures of metabolic rate during immune challenges contradict this assumption. The energetic cost of APR for birds is higher than for rodents, suggesting that this response is less expensive for mammals. However, the particularly large increase in metabolic rate after APR activation for a piscivorous bat (Myotis vivesi) suggests that immune response might be unusually costly for bats. Here we quantified the energetic cost and body mass change associated with APR for the nectarivorous Pallas's long-tongued bat (Glossophaga soricina). Activation of the APR resulted in a short-term decrease in body mass and an increase in resting metabolic rate (RMR) with a total energy cost of only 2% of the total energy expenditure estimated for G. soricina. This increase in RMR was far from the large increase measured for piscivorous bats; rather, it was similar to the highest values reported for birds. Overall, our results suggest that the costs of APR for bats may vary interspecifically. Measurement of the energy cost of vertebrate immune response is limited to a few species and further work is warranted to evaluate its significance for an animal's energy budget.
Project description:Thomas Hunt Morgan and colleagues identified variation in gene copy number in Drosophila in the 1920s and 1930s and linked such variation to phenotypic differences [Bridges, C. B. (1936) Science 83, 210]. Yet the extent of variation in the number of chromosomes, chromosomal regions, or gene copies, and the importance of this variation within species, remain poorly understood. Here, we focus on copy-number variation in Drosophila melanogaster. We characterize copy-number polymorphism (CNP) across genomic regions, and we contrast patterns to infer the evolutionary processes acting on this variation. Copy-number variation in D. melanogaster is non-randomly distributed, presumably due to a mutational bias produced by tandem repeats or other mechanisms. Comparisons of coding and noncoding CNPs, however, reveal a strong effect of purifying selection in the removal of structural variation from functionally constrained regions. Most patterns of CNP in D. melanogaster suggest that negative selection and mutational biases are the primary agents responsible for shaping structural variation. Keywords: comparative genomic hybridization
Project description:Chromatin accessibility is a hallmark of active regulatory function in the genome and variation of chromatin accessibility across individuals has been shown to contribute to complex traits and disease susceptibility. However, the mechanisms responsible for chromatin variation among different individuals and how this variation contributes to phenotypic diversity remain poorly understood. We examined chromatin accessibility variation in liver tissue from seven strains of adult mice that have phenotypic diversity in response to a high-fat/high-sucrose diet. Remarkably, nearly 40% of the loci with the greatest degree of chromatin variability across the strains are associated with transposable elements (TEs), with evolutionarily younger TEs being particularly enriched for regions of chromatin variation. We found that evolutionary younger and older TEs have differential chromatin accessibility profiles and are enriched for binding sites of different transcription factors, indicating the role of TEs in the evolution of regulatory networks in the liver. We also demonstrate that TE polymorphisms and epigenetic regulation of TEs contribute to regulatory variation across different strains through providing binding sites for liver transcription factors. Intriguingly, variable chromatin loci that are associated with liver metabolism are primarily TE-associated. We demonstrate that TEs contribute to regulatory variation in liver and have downstream effects on metabolism. Our data reveal TEs as a novel and important contributor to regulatory and phenotypic variation in the liver and suggest that regulatory variation at TEs is a major contributor to phenotypic variation in populations. Examination of chromatin accessibility with FAIRE-seq in livers of male mice (A/J, AKR/J, BALB/cJ, C57BL/6J, C3H/HeJ, CBA/J, DBA/2J, BXH2/TyJ, and BXH19/TyJ) fed a high-fat, high-sucrose diet.