title: Population and sex differences in Drosophila melanogaster brain gene expression.
abstract: BACKGROUND
  Changes in gene regulation are thought to be crucial for the adaptation of organisms to their environment. Transcriptome analyses can be used to identify candidate genes for ecological adaptation, but can be complicated by variation in gene expression between tissues, sexes, or individuals. Here we use high-throughput RNA sequencing of a single Drosophila melanogaster tissue to detect brain-specific differences in gene expression between the sexes and between two populations, one from the ancestral species range in sub-Saharan Africa and one from the recently colonized species range in Europe.
  
  
  RESULTS
  Relatively few genes (<100) displayed sexually dimorphic expression in the brain, but there was an enrichment of sex-biased genes, especially male-biased genes, on the X chromosome. Over 340 genes differed in brain expression between flies from the African and European populations, with the inter-population divergence being highly correlated between males and females. The differentially expressed genes included those involved in stress response, olfaction, and detoxification. Expression differences were associated with transposable element insertions at two genes implicated in insecticide resistance (Cyp6g1 and CHKov1).
  
  
  CONCLUSIONS
  Analysis of the brain transcriptome revealed many genes differing in expression between populations that were not detected in previous studies using whole flies. There was little evidence for sex-specific regulatory adaptation in the brain, as most expression differences between populations were observed in both males and females. The enrichment of genes with sexually dimorphic expression on the X chromosome is consistent with dosage compensation mechanisms affecting sex-biased expression in somatic tissues.
authors.affiliation: Department of Biology II, University of Munich (LMU), Grosshaderner Str. 2, Planegg-Martinsried 82152, Germany.
authors.forename: Ana
authors.initials: A
authors.lastname: Catalán
authors.forename: Stephan
authors.initials: S
authors.lastname: Hutter
authors.forename: John
authors.initials: J
authors.lastname: Parsch
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004251:DNA Transposable Elements; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000145:classification / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D017344:Genes, Insect; D059014:High-Throughput Nucleotide Sequencing; D007305:Insecticide Resistance / Q000235:genetics; D008297:Male; D016254:Mutagenesis, Insertional; D009426:Netherlands; D010802:Phylogeny; D058974:Phylogeography; D012727:Sex Characteristics; D012903:Smell / Q000235:genetics; D013312:Stress, Physiological; D059467:Transcriptome; D015030:Zimbabwe
chemical_list: D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D003577:Cytochrome P-450 Enzyme System; C446928:Cyp6g1 protein, Drosophila