Systems genetics analysis of body weight and energy metabolism traits in Drosophila melanogaster

<p>Abstract</p> <p>Background</p> <p>Obesity and phenotypic traits associated with this condition exhibit significant heritability in natural populations of most organisms. While a number of genes and genetic pathways have been implicated to play a role in obesity associated traits, the genetic architecture that underlies the natural variation in these traits is largely unknown. Here, we used 40 wild-derived inbred lines of <it>Drosophila melanogaster </it>to quantify genetic variation in body weight, the content of three major metabolites (glycogen, triacylglycerol, and glycerol) associated with obesity, and metabolic rate in young flies. We chose these lines because they were previously screened for variation in whole-genome transcript abundance and in several adult life-history traits, including longevity, resistance to starvation stress, chill-coma recovery, mating behavior, and competitive fitness. This enabled us not only to identify candidate genes and transcriptional networks that might explain variation for energy metabolism traits, but also to investigate the genetic interrelationships among energy metabolism, behavioral, and life-history traits that have evolved in natural populations.</p> <p>Results</p> <p>We found significant genetically based variation in all traits. Using a genome-wide association screen for single feature polymorphisms and quantitative trait transcripts, we identified 337, 211, 237, 553, and 152 novel candidate genes associated with body weight, glycogen content, triacylglycerol storage, glycerol levels, and metabolic rate, respectively. Weighted gene co-expression analyses grouped transcripts associated with each trait in significant modules of co-expressed genes and we interpreted these modules in terms of their gene enrichment based on Gene Ontology analysis. Comparison of gene co-expression modules for traits in this study with previously determined modules for life-history traits identified significant modular pleiotropy between glycogen content, body weight, competitive fitness, and starvation resistance.</p> <p>Conclusions</p> <p>Combining a large phenotypic dataset with information on variation in genome wide transcriptional profiles has provided insight into the complex genetic architecture underlying natural variation in traits that have been associated with obesity. Our findings suggest that understanding the maintenance of genetic variation in metabolic traits in natural populations may require that we understand more fully the degree to which these traits are genetically correlated with other traits, especially those directly affecting fitness.</p

A Conserved Role for Syndecan Family Members in the Regulation of Whole-Body Energy Metabolism

Syndecans are a family of type-I transmembrane proteins that are involved in cell-matrix adhesion, migration, neuronal development, and inflammation. Previous quantitative genetic studies pinpointed Drosophila Syndecan (dSdc) as a positional candidate gene affecting variation in fat storage between two Drosophila melanogaster strains. Here, we first used quantitative complementation tests with dSdc mutants to confirm that natural variation in this gene affects variability in Drosophila fat storage. Next, we examined the effects of a viable dSdc mutant on Drosophila whole-body energy metabolism and associated traits. We observed that young flies homozygous for the dSdc mutation had reduced fat storage and slept longer than homozygous wild-type flies. They also displayed significantly reduced metabolic rate, lower expression of spargel (the Drosophila homologue of PGC-1), and reduced mitochondrial respiration. Compared to control flies, dSdc mutants had lower expression of brain insulin-like peptides, were less fecund, more sensitive to starvation, and had reduced life span. Finally, we tested for association between single nucleotide polymorphisms (SNPs) in the human SDC4 gene and variation in body composition, metabolism, glucose homeostasis, and sleep traits in a cohort of healthy early pubertal children. We found that SNP rs4599 was significantly associated with resting energy expenditure (P = 0.001 after Bonferroni correction) and nominally associated with fasting glucose levels (P = 0.01) and sleep duration (P = 0.044). On average, children homozygous for the minor allele had lower levels of glucose, higher resting energy expenditure, and slept shorter than children homozygous for the common allele. We also observed that SNP rs1981429 was nominally associated with lean tissue mass (P = 0.035) and intra-abdominal fat (P = 0.049), and SNP rs2267871 with insulin sensitivity (P = 0.037). Collectively, our results in Drosophila and humans argue that syndecan family members play a key role in the regulation of body metabolism

Foraging Assay for DRYAD

Foraging rates of different Ddc genotype

Dopamine data for DRYAD

These data are dopamine levels for the different Ddc genotypes

Laboratory Encapsulation ability for DRYAD

Encapsulation ability of different Ddc genotypes exposed to Leptopilina and Aphaereta wasp

Laboratory Attack Rate Data for DRYAD

Attack rate of Leptopilina and Aphaereta on different Ddc genotype

Field Attack Rate Data for DRYAD

These data are for the attack rates of wasps on the different Ddc genotypes in the field

feeding rate for DRYAD

These data are for feeding rates of different Ddc genotype

Review of the genus Leptopilina (Hymenoptera, Cynipoidea, Figitidae, Eucoilinae) from the Eastern United States, including three newly described species

The genus Leptopilina has historically been a poorly understood group. However, some species of Leptopilina are among the best-known model organisms for studying host-parasitoid interactions. As there is no identification system for Leptopilina in any part of the United States, we review species that were collected throughout their range in Eastern North America and those commonly used in laboratories. We provide a key for seven species, L. boulardi, L. heterotoma, L. clavipes, L. victoriae, L. decemflagella sp. n., L. maia sp. n. and L. leipsi sp. n., the last three of which are newly described here. This study is the first of its kind for Leptopilina species in North America, as our review and key were developed by examining a large number of specimens collected across broad chronological and geographic scales. This allowed us to account for the phenotypic variation within species, and helped us discover diagnostic characters. The geographic distribution and taxonomic information from this review provides a solid foundation for future research on Leptopilina