A frog with three sex chromosomes that co-mingle together in nature: Xenopus tropicalis has a degenerate W and a Y that evolved from a Z chromosome

Autoři: Benjamin L. S. Furman aff001;  Caroline M. S. Cauret aff001;  Martin Knytl aff001;  Xue-Ying Song aff001;  Tharindu Premachandra aff001;  Caleb Ofori-Boateng aff004;  Danielle C. Jordan aff005;  Marko E. Horb aff005;  Ben J. Evans aff001
Působiště autorů: Department of Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada aff001;  Department of Zoology, University of British Columbia, 6270 University Blvd Vancouver, British Columbia, V6T 1Z4 Canada aff002;  Department of Cell Biology, Charles University, 7 Vinicna Street, Prague, 12843, Czech Republic aff003;  CSIR-Forestry Research Institute of Ghana, Kumasi, Ghana aff004;  Eugene Bell Center for Regenerative Biology and Tissue Engineering and National Resource, Marine Biological Laboratory, 7 MBL St, Woods Hole, MA 02543 USA aff005
Vyšlo v časopise: A frog with three sex chromosomes that co-mingle together in nature: Xenopus tropicalis has a degenerate W and a Y that evolved from a Z chromosome. PLoS Genet 16(11): e1009121. doi:10.1371/journal.pgen.1009121
Kategorie: Research Article
doi: 10.1371/journal.pgen.1009121


In many species, sexual differentiation is a vital prelude to reproduction, and disruption of this process can have severe fitness effects, including sterility. It is thus interesting that genetic systems governing sexual differentiation vary among—and even within—species. To understand these systems more, we investigated a rare example of a frog with three sex chromosomes: the Western clawed frog, Xenopus tropicalis. We demonstrate that natural populations from the western and eastern edges of Ghana have a young Y chromosome, and that a male-determining factor on this Y chromosome is in a very similar genomic location as a previously known female-determining factor on the W chromosome. Nucleotide polymorphism of expressed transcripts suggests genetic degeneration on the W chromosome, emergence of a new Y chromosome from an ancestral Z chromosome, and natural co-mingling of the W, Z, and Y chromosomes in the same population. Compared to the rest of the genome, a small sex-associated portion of the sex chromosomes has a 50-fold enrichment of transcripts with male-biased expression during early gonadal differentiation. Additionally, X. tropicalis has sex-differences in the rates and genomic locations of recombination events during gametogenesis that are similar to at least two other Xenopus species, which suggests that sex differences in recombination are genus-wide. These findings are consistent with theoretical expectations associated with recombination suppression on sex chromosomes, demonstrate that several characteristics of old and established sex chromosomes (e.g., nucleotide divergence, sex biased expression) can arise well before sex chromosomes become cytogenetically distinguished, and show how these characteristics can have lingering consequences that are carried forward through sex chromosome turnovers.

Klíčová slova:

Genomics – Ghana – Sex chromosomes – Single nucleotide polymorphisms – X chromosomes – Y chromosomes – W chromosomes – Z chromosomes


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