Publication Date:
2010-07-14
Description:
In birds, as in mammals, one pair of chromosomes differs between the sexes. In birds, males are ZZ and females ZW. In mammals, males are XY and females XX. Like the mammalian XY pair, the avian ZW pair is believed to have evolved from autosomes, with most change occurring in the chromosomes found in only one sex--the W and Y chromosomes. By contrast, the sex chromosomes found in both sexes--the Z and X chromosomes--are assumed to have diverged little from their autosomal progenitors. Here we report findings that challenge this assumption for both the chicken Z chromosome and the human X chromosome. The chicken Z chromosome, which we sequenced essentially to completion, is less gene-dense than chicken autosomes but contains a massive tandem array containing hundreds of duplicated genes expressed in testes. A comprehensive comparison of the chicken Z chromosome with the finished sequence of the human X chromosome demonstrates that each evolved independently from different portions of the ancestral genome. Despite this independence, the chicken Z and human X chromosomes share features that distinguish them from autosomes: the acquisition and amplification of testis-expressed genes, and a low gene density resulting from an expansion of intergenic regions. These features were not present on the autosomes from which the Z and X chromosomes originated but were instead acquired during the evolution of Z and X as sex chromosomes. We conclude that the avian Z and mammalian X chromosomes followed convergent evolutionary trajectories, despite their evolving with opposite (female versus male) systems of heterogamety. More broadly, in birds and mammals, sex chromosome evolution involved not only gene loss in sex-specific chromosomes, but also marked expansion and gene acquisition in sex chromosomes common to males and females.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943333/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉 〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943333/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bellott, Daniel W -- Skaletsky, Helen -- Pyntikova, Tatyana -- Mardis, Elaine R -- Graves, Tina -- Kremitzki, Colin -- Brown, Laura G -- Rozen, Steve -- Warren, Wesley C -- Wilson, Richard K -- Page, David C -- R01 HG000257/HG/NHGRI NIH HHS/ -- R01 HG000257-21/HG/NHGRI NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2010 Jul 29;466(7306):612-6. doi: 10.1038/nature09172. Epub 2010 Jul 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20622855" target="_blank"〉PubMed〈/a〉
Keywords:
Animals
;
Chickens/*genetics
;
Chromosomes, Human, X/*genetics
;
*Evolution, Molecular
;
Female
;
Gene Deletion
;
Genes/*genetics
;
Genome/genetics
;
Humans
;
Male
;
Multigene Family/genetics
;
Sex Characteristics
;
Sex Chromosomes/*genetics
;
Testis/metabolism
Print ISSN:
0028-0836
Electronic ISSN:
1476-4687
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
,
Natural Sciences in General
,
Physics
