Sequence analysis in Bos taurus reveals pervasiveness of X–Y arms races in mammalian lineages

Sequence analysis in Bos taurus reveals pervasiveness of X–Y arms races in mammalian lineages

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J. F. Hughes, H. Skaletsky, T. Pyntikova, N. Koutseva, T. Raudsepp, L. G. Brown, D. W. Bellott, T.-J. Cho, S. Dugan-Rocha, Z. Khan, C. Kremitzki, C. Fronick, T. A. Graves-Lindsay, L. Fulton, W. C. Warren, R. K. Wilson, E. Owens, J. E. Womack, W. J. Murphy,  Genome Research,  2020.

Studies of Y Chromosome evolution have focused primarily on gene decay, a consequence of suppression of crossing-over with the X Chromosome. Here, we provide evidence that suppression of X–Y crossing-over unleashed a second dynamic: selfish X–Y arms races that reshaped the sex chromosomes in mammals as different as cattle, mice, and men. Using super-resolution sequencing, we explore the Y Chromosome of Bos taurus (bull) and find it to be dominated by massive, lineage-specific amplification of testis-expressed gene families, making it the most gene-dense Y Chromosome sequenced to date. As in mice, an X-linked homolog of a bull Y-amplified gene has become testis-specific and amplified. This evolutionary convergence implies that lineage-specific X–Y coevolution through gene amplification, and the selfish forces underlying this phenomenon, were dominatingly powerful among diverse mammalian lineages. Together with Y gene decay, X–Y arms races molded mammalian sex chromosomes and influenced the course of mammalian evolution.