Demasculinization of X chromosomes in the Drosophila genus.
X chromosomes evolve differently from autosomes, but general governing principles have not emerged. For example, genes with male-biased expression are under-represented on the X chromosome of D. melanogaster, but are randomly distributed in the genome of Anopheles gambiae. In direct global profiling experiments using species-specific microarrays, we find a nearly identical paucity of genes with male-biased expression on D. melanogaster, D. simulans, D. yakuba, D. ananassae, D. virilis and D. mojavensis X chromosomes. We observe the same under-representation on the neo-X of D. pseudoobscura. It has been suggested that precocious meiotic silencing of the X chromosome accounts for reduced X chromosome male-biased expression in nematodes, mammals and Drosophila. We show that X chromosome genes with male-biased expression are under-represented in somatic cells and in mitotic male germ cells. These data are incompatible with simple X chromosome inactivation models. Using expression profiling and comparative sequence analysis, we show that selective gene extinction on the X chromosome, creation of new genes on autosomes and changed genomic location of existing genes contribute to the unusual X chromosome gene content.
Sturgill
David
D
Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda Maryland 20892, USA. davidsturgill@niddk.nih.gov
Zhang
Yu
Y
Parisi
Michael
M
Oliver
Brian
B
D000818:Animals; D004330:Drosophila / Q000145:classification / Q000235:genetics*; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000235:genetics*; D008297:Male; D008957:Models, Genetic; D012727:Sex Characteristics; D014960:X Chromosome / Q000235:genetics*; D049951:X Chromosome Inactivation