The process of a Y-loss event in an XO/XO mammal, the Ryukyu spiny rat
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The Ryukyu spiny rat, Tokudaia osimensis, has an XO/XO sex chromosome constitution, lacking a Y chromosome and the mammalian sex-determining gene SRY. To investigate the Y-loss event, we traced three proto-Y-linked genes, RBMY1A1, EIF2S3Y, and KDM5D, in the genome. The original Y-linked RBMY1A1 was lost as well as SRY, and the remaining RBMY1A1 was a processed pseudogene on autosome. In contrast, EIF2S3Y and KDM5D were conserved in genomes of both sexes as a result of their translocation from the Y chromosome to the X chromosome and/or autosomes. Furthermore, these genes were expressed in gonads and brains of both sexes. Our study indicated a loss of Y-linked genes with important male functions to be necessary for the Y chromosome to disappear. These functions might have been retained through the acquisition of new genes, and therefore, the Y-loss has had no harmful effect on the maintenance of this species.
KeywordsSaline Sodium Citrate Mouse Genome Informatics Mouse cDNA Clone Takara Biomedical H3K4 Demethylase Activity
The authors thank K. Matsubara and C. Nishida-Umehara for their advice on cell culture and chromosome banding; T. Hashimoto, K. Sato, and N. Ishii for their efforts in capturing the animals; and M. Komoto for an additional experiment. This work is supported by Grants-in-aid for Scientific Research (No. 16086201) from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and the Global Environment Research Fund F-3 (for FY) from the Ministry of the Environment, Japan, and a grant from the Inamori Foundation, Japan.
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