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The Wright stuff: reimagining path analysis reveals novel components of the sex determination hierarchy in Drosophila melanogaster.

ABSTRACT: BACKGROUND:The Drosophila sex determination hierarchy is a classic example of a transcriptional regulatory hierarchy, with sex-specific isoforms regulating morphology and behavior. We use a structural equation modeling approach, leveraging natural genetic variation from two studies on Drosophila female head tissues--DSPR collection (596 F1-hybrids from crosses between DSPR sub-populations) and CEGS population (75 F1-hybrids from crosses between DGRP/Winters lines to a reference strain w1118)--to expand understanding of the sex hierarchy gene regulatory network (GRN). This approach is completely generalizable to any natural population, including humans. RESULTS:We expanded the sex hierarchy GRN adding novel links among genes, including a link from fruitless (fru) to Sex-lethal (Sxl) identified in both populations. This link is further supported by the presence of fru binding sites in the Sxl locus. 754 candidate genes were added to the pathway, including the splicing factors male-specific lethal 2 and Rm62 as downstream targets of Sxl which are well-supported links in males. Independent studies of doublesex and transformer mutants support many additions, including evidence for a link between the sex hierarchy and metabolism, via Insulin-like receptor. CONCLUSIONS:The genes added in the CEGS population were enriched for genes with sex-biased splicing and components of the spliceosome. A common goal of molecular biologists is to expand understanding about regulatory interactions among genes. Using natural alleles we can not only identify novel relationships, but using supervised approaches can order genes into a regulatory hierarchy. Combining these results with independent large effect mutation studies, allows clear candidates for detailed molecular follow-up to emerge.

SUBMITTER: Fear JM

PROVIDER: S-EPMC4558766 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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The Wright stuff: reimagining path analysis reveals novel components of the sex determination hierarchy in Drosophila melanogaster.

Fear Justin M JM Arbeitman Michelle N MN Salomon Matthew P MP Dalton Justin E JE Tower John J Nuzhdin Sergey V SV McIntyre Lauren M LM

BMC systems biology 20150904

<h4>Background</h4>The Drosophila sex determination hierarchy is a classic example of a transcriptional regulatory hierarchy, with sex-specific isoforms regulating morphology and behavior. We use a structural equation modeling approach, leveraging natural genetic variation from two studies on Drosophila female head tissues--DSPR collection (596 F1-hybrids from crosses between DSPR sub-populations) and CEGS population (75 F1-hybrids from crosses between DGRP/Winters lines to a reference strain w1 ...[more]

PMID: 26335107

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Project description:The Drosophila sex determination hierarchy consists of a splicing cascade with sex-specific transcription directing somatic sexual dimorphism. Our understanding of this pathway, and many others, is incomplete. Here we pioneer an approach to expand our knowledge of gene regulatory networks (GRNs) by leveraging natural genetic variation. This approach is generalizable to any natural population, including humans. Two studies from Drosophila female head tissue were used – the DSPR collection (alleles from 15 natural variants) and F1-hybrid collection (alleles from heterozygotes of 75 isogenic lines crossed to w1118) – in a structural equation model (SEM) analysis. We expanded the sex hierarchy GRN by adding novel links among genes in the pathway and by adding novel genes to the pathway. A link from fruitless (fru) to Sex-lethal (Sxl) was found in both populations, which is supported by the presence of fru binding sites in the Sxl locus. The splicing factors male-specific lethal 2 and Rm62 were correctly identified as downstream targets of Sxl. There were 754 additional candidate genes for an expanded sex hierarchy GRN. These candidates were enriched for genes with sex-biased splicing and many components of the spliceosome were placed in the GRN. As with other population-genetic analyses, the number of alleles limits the number of observable interactions. Network expansion was only clear in the F1-hybrid population, which has an average of twice as many alleles as the DSPR population. Independent studies of doublesex and transformer mutants support many novel connections, including evidence for a link between the sex hierarchy and metabolism, with the inclusion of Insulin-like receptor in the sex hierarchy GRN. RNA sequencing was performed on mRNA derived from adult male or female heads, for a total of 9 samples. These samples included females that produce the male isoform of dsx [w/+;DsxD/dsxm+r15 (XX)], and two dsx mutants: females [w/+; dsxm+r15/dsxd+r3 (XX)] and males [w;dsxm+r15/dsxd+r3 (XY)]. Two wild type genotypes (Berlin and Canton-S) were sequenced at the same time, but have previously been published as part of GSE50515. There were at least 3 replicates from biological samples.

Project description:BACKGROUND:Drosophila melanogaster undergoes a complete metamorphosis, during which time the larval male and female forms transition into sexually dimorphic, reproductive adult forms. To understand this complex morphogenetic process at a molecular-genetic level, whole genome microarray analyses were performed. RESULTS:The temporal gene expression patterns during metamorphosis were determined for all predicted genes, in both somatic and germline tissues of males and females separately. Temporal changes in transcript abundance for genes of known functions were found to correlate with known developmental processes that occur during metamorphosis. We find that large numbers of genes are sex-differentially expressed in both male and female germline tissues, and relatively few are sex-differentially expressed in somatic tissues. The majority of genes with somatic, sex-differential expression were found to be expressed in a stage-specific manner, suggesting that they mediate discrete developmental events. The Sex-lethal paralog, CG3056, displays somatic, male-biased expression at several time points in metamorphosis. Gene expression downstream of the somatic, sex determination genes transformer and doublesex (dsx) was examined in two-day old pupae, which allowed for the identification of genes regulated as a consequence of the sex determination hierarchy. These include the homeotic gene abdominal A, which is more highly expressed in females as compared to males, as a consequence of dsx. For most genes regulated downstream of dsx during pupal development, the mode of regulation is distinct from that observed for the well-studied direct targets of DSX, Yolk protein 1 and 2. CONCLUSION:The data and analyses presented here provide a comprehensive assessment of gene expression during metamorphosis in each sex, in both somatic and germline tissues. Many of the genes that underlie critical developmental processes during metamorphosis, including sex-specific processes, have been identified. These results provide a framework for further functional studies on the regulation of sex-specific development.

Dataset Information

The Wright stuff: reimagining path analysis reveals novel components of the sex determination hierarchy in Drosophila melanogaster.

Publications

The Wright stuff: reimagining path analysis reveals novel components of the sex determination hierarchy in Drosophila melanogaster.

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