Sex Chromosome Transformation and the Origin of a Male-Specific X Chromosome in the Creeping Vole.
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 () 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 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 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.
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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