title: Comparative mapping of Z-orthologous genes in vertebrates: implications for the evolution of avian sex chromosomes.
abstract: Sex chromosomes of birds and mammals are highly differentiated and share several cytological features. However, comparative gene mapping reveals extensive conserved synteny between the chicken Z sex chromosome and human chromosome 9 but not the human X sex chromosome, implying an independent origin of avian and mammalian sex chromosomes. To better understand the evolution of the avian Z chromosome we analysed the synteny of chicken Z-linked genes in zebrafish, which is the best-mapped teleost genome so far. Existing zebrafish maps do not support the existence of an ancestral Z linkage group in the zebrafish genome, whereas mammalian X-linked genes show at least some degree of synteny conservation. This is consistent with in situ hybridisation mapping data in the freshwater pufferfish, Tetraodon nigroviridis where mammalian X-linked genes show a much higher degree of conserved synteny than human chromosome 9 or the avian Z chromosome. Collectively, these data argue in favour of a more recent evolution of the avian Z chromosome, compared with the mammalian X.
authors.affiliation: Department of Human Genetics, Würzburg, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Nanda
authors.forename: T
authors.initials: T
authors.lastname: Haaf
authors.forename: M
authors.initials: M
authors.lastname: Schartl
authors.forename: M
authors.initials: M
authors.lastname: Schmid
authors.forename: D W
authors.initials: DW
authors.lastname: Burt
mesh_terms: D000818:Animals; D002645:Chickens; D002874:Chromosome Mapping; D019143:Evolution, Molecular; D006801:Humans; D012730:Sex Chromosomes / Q000235:genetics*; D026801:Synteny; D014714:Vertebrates / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics