title: Genomic analysis of the relationship between gene expression variation and DNA polymorphism in Drosophila simulans.
abstract: BACKGROUND
  Understanding how DNA sequence polymorphism relates to variation in gene expression is essential to connecting genotypic differences with phenotypic differences among individuals. Addressing this question requires linking population genomic data with gene expression variation.
  
  
  RESULTS
  Using whole genome expression data and recent light shotgun genome sequencing of six Drosophila simulans genotypes, we assessed the relationship between expression variation in males and females and nucleotide polymorphism across thousands of loci. By examining sequence polymorphism in gene features, such as untranslated regions and introns, we find that genes showing greater variation in gene expression between genotypes also have higher levels of sequence polymorphism in many gene features. Accordingly, X-linked genes, which have lower sequence polymorphism levels than autosomal genes, also show less expression variation than autosomal genes. We also find that sex-specifically expressed genes show higher local levels of polymorphism and divergence than both sex-biased and unbiased genes, and that they appear to have simpler regulatory regions.
  
  
  CONCLUSIONS
  The gene-feature-based analyses and the X-to-autosome comparisons suggest that sequence polymorphism in cis-acting elements is an important determinant of expression variation. However, this relationship varies among the different categories of sex-biased expression, and trans factors might contribute more to male-specific gene expression than cis effects. Our analysis of sex-specific gene expression also shows that female-specific genes have been overlooked in analyses that only point to male-biased genes as having unusual patterns of evolution and that studies of sexually dimorphic traits need to recognize that the relationship between genetic and expression variation at these traits is different from the genome as a whole.
authors.affiliation: Division of Cell and Molecular Biology, Imperial College London, London, SW7 2AZ, UK. m.lawniczak@imperial.ac.uk
authors.forename: Mara K N
authors.initials: MK
authors.lastname: Lawniczak
authors.forename: Alisha K
authors.initials: AK
authors.lastname: Holloway
authors.forename: David J
authors.initials: DJ
authors.lastname: Begun
authors.forename: Corbin D
authors.initials: CD
authors.lastname: Jones
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics*; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics*; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D050172:Genes, X-Linked; D023281:Genomics; D005838:Genotype; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D011110:Polymorphism, Genetic; D012737:Sex Factors
chemical_list: D029721:Drosophila Proteins