title: Independent specialization of the human and mouse X chromosomes for the male germ line.
abstract: We compared the human and mouse X chromosomes to systematically test Ohno's law, which states that the gene content of X chromosomes is conserved across placental mammals. First, we improved the accuracy of the human X-chromosome reference sequence through single-haplotype sequencing of ampliconic regions. The new sequence closed gaps in the reference sequence, corrected previously misassembled regions and identified new palindromic amplicons. Our subsequent analysis led us to conclude that the evolution of human and mouse X chromosomes was bimodal. In accord with Ohno's law, 94-95% of X-linked single-copy genes are shared by humans and mice; most are expressed in both sexes. Notably, most X-ampliconic genes are exceptions to Ohno's law: only 31% of human and 22% of mouse X-ampliconic genes had orthologs in the other species. X-ampliconic genes are expressed predominantly in testicular germ cells, and many were independently acquired since divergence from the common ancestor of humans and mice, specializing portions of their X chromosomes for sperm production.
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Mueller
authors.forename: Helen
authors.initials: H
authors.lastname: Skaletsky
authors.forename: Laura G
authors.initials: LG
authors.lastname: Brown
authors.forename: Sara
authors.initials: S
authors.lastname: Zaghlul
authors.forename: Susan
authors.initials: S
authors.lastname: Rock
authors.forename: Tina
authors.initials: T
authors.lastname: Graves
authors.forename: Katherine
authors.initials: K
authors.lastname: Auger
authors.forename: Wesley C
authors.initials: WC
authors.lastname: Warren
authors.forename: Richard K
authors.initials: RK
authors.lastname: Wilson
authors.forename: David C
authors.initials: DC
authors.lastname: Page
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D019295:Computational Biology; D019143:Evolution, Molecular; D050172:Genes, X-Linked; D023281:Genomics; D005854:Germ Cells / Q000378:metabolism*; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D014960:X Chromosome / Q000737:chemistry / Q000235:genetics*