title: High expression of the mammalian X chromosome in brain.
abstract: Divergence between the sex chromosomes has led to loss and differentiation of Y-linked genes and haplo-insufficiency for X-linked genes in males. A mechanism of dosage compensation, for which we recently found evidence in mammals, evolved to restore a balanced expression of the genome by doubling the transcriptional output from the X chromosome. X inactivation would then serve to avoid hyper-transcription of X-linked genes in females by silencing one X chromosome. We also found that, compared to the rest of the genome, the X chromosome contains an excess of genes highly expressed in brain tissues. The exceptionally important role of the X chromosome in brain function, evident from the prevalence of X-linked forms of mental retardation, is discussed in view of sex chromosome regulation and evolution and sexual reproduction.
authors.affiliation: Department of Pathology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Di Kim
authors.initials: DK
authors.lastname: Nguyen
authors.forename: Christine M
authors.initials: CM
authors.lastname: Disteche
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology* / Q000254:growth & development / Q000378:metabolism; D001923:Brain Chemistry / Q000235:genetics*; D004303:Dosage Compensation, Genetic / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D040181:Genetic Diseases, X-Linked / Q000235:genetics; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics*; D012733:Sex Differentiation / Q000235:genetics; D014960:X Chromosome / Q000235:genetics*; D049951:X Chromosome Inactivation / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics