Sex Chromosome Transformation and the Origin of a Male-Specific X Chromosome in the Creeping Vole.
This work was funded by National Science Foundation IOS 1558109 and start-up funds from the University of California, Riverside (P.C.), National Science Foundation MCB 1616878 (S.W.R.), and National Institutes of Health R44GM134994 (K.J.L.).
Science (new York, N.Y.)
The mammalian sex chromosome system (XX female/XY male) is ancient and highly conserved. The sex chromosome karyotype of the creeping vole (Microtus oregoni) represents a long-standing anomaly, with an X chromosome that is unpaired in females (X0) and exclusively maternally transmitted. We produced a highly contiguous male genome assembly, together with short-read genomes and transcriptomes for both sexes. We show that M. oregoni has lost an independently segregating Y chromosome and that the male-specific sex chromosome is a second X chromosome that is largely homologous to the maternally transmitted X. Both maternally inherited and male-specific sex chromosomes carry fragments of the ancestral Y chromosome. Consequences of this recently transformed sex chromosome system include Y-like degeneration and gene amplification on the male-specific X, expression of ancestral Y-linked genes in females, and X inactivation of the male-specific chromosome in male somatic cells. The genome of M. oregoni elucidates the processes that shape the gene content and dosage of mammalian sex chromosomes and exemplifies a rare case of plasticity in an ancient sex chromosome system.
© 2021 American Association for the Advancement of Science.
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Couger, M. B., Roy, S. W., Anderson, N., Gozashti, L., Pirro, S., Millward, L. S., Kim, M., Kilburn, D., Liu, K. J., Wilson, T. M., Epps, C. W., Dizney, L., Ruedas, L. A., & Campbell, P. (2021). Sex chromosome transformation and the origin of a male-specific X chromosome in the creeping vole. Science, 372(6542), 592–600. https://doi.org/10.1126/science.abg7019