title: Avian W and mammalian Y chromosomes convergently retained dosage-sensitive regulators.
abstract: After birds diverged from mammals, different ancestral autosomes evolved into sex chromosomes in each lineage. In birds, females are ZW and males are ZZ, but in mammals females are XX and males are XY. We sequenced the chicken W chromosome, compared its gene content with our reconstruction of the ancestral autosomes, and followed the evolutionary trajectory of ancestral W-linked genes across birds. Avian W chromosomes evolved in parallel with mammalian Y chromosomes, preserving ancestral genes through selection to maintain the dosage of broadly expressed regulators of key cellular processes. We propose that, like the human Y chromosome, the chicken W chromosome is essential for embryonic viability of the heterogametic sex. Unlike other sequenced sex chromosomes, the chicken W chromosome did not acquire and amplify genes specifically expressed in reproductive tissues. We speculate that the pressures that drive the acquisition of reproduction-related genes on sex chromosomes may be specific to the male germ line.
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.|Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Bellott
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.|Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Helen
authors.initials: H
authors.lastname: Skaletsky
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Ting-Jan
authors.initials: TJ
authors.lastname: Cho
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.|Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Brown
authors.affiliation: McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Devin
authors.initials: D
authors.lastname: Locke
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA.|Cornell Laboratory of Ornithology, Ithaca, New York, USA.|Department of Evolution and Ecology, University of California, Davis, Davis, California, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Chen
authors.affiliation: Saint Petersburg State University, Saint Petersburg, Russian Federation.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Galkina
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Pyntikova
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: Natalia
authors.initials: N
authors.lastname: Koutseva
authors.affiliation: McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Tina
authors.initials: T
authors.lastname: Graves
authors.affiliation: McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Colin
authors.initials: C
authors.lastname: Kremitzki
authors.affiliation: McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Wesley C
authors.initials: WC
authors.lastname: Warren
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA.|Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York, USA.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Clark
authors.affiliation: Saint Petersburg State University, Saint Petersburg, Russian Federation.
authors.forename: Elena
authors.initials: E
authors.lastname: Gaginskaya
authors.affiliation: McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Wilson
authors.affiliation: Whitehead Institute, Cambridge, Massachusetts, USA.|Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.|Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts, USA.
authors.forename: David C
authors.identifier: http://orcid.org/0000-0001-5489-6453
authors.initials: DC
authors.lastname: Page
mesh_terms: D000818:Animals; D001717:Birds / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D018628:Gene Dosage / Q000235:genetics*; D006801:Humans; D008297:Male; D008322:Mammals / Q000235:genetics*; D019849:Sex Determination Processes / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics*
chemical_list: D014157:Transcription Factors