TY - JOUR T1 - Differential sperm motility mediates the sex ratio drive shaping mouse sex chromosome evolution JF - bioRxiv DO - 10.1101/649707 SP - 649707 AU - CC Rathje AU - EEP Johnson AU - D Drage AU - C Patinioti AU - G Silvestri AU - NA Affara AU - C Ialy-Radio AU - J Cocquet AU - BM Skinner AU - PJI Ellis Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/05/24/649707.abstract N2 - Summary The search for morphological or physiological differences between X- and Y-bearing mammalian sperm has provoked controversy for decades. Many potential differences have been proposed, but none validated, while accumulating understanding of syncytial sperm development has cast doubt on whether such differences are possible even in principle. We present the first ever mammalian experimental model to trace a direct link from a measurable physiological difference between X- and Y-bearing sperm to the resulting skewed sex ratio. We show that in mice with deletions on chromosome Yq, birth sex ratio distortion is due to a relatively greater motility of X-bearing sperm, and not to any aspect of sperm/egg interaction. Moreover, the morphological distortion caused by Yq deletion is more severe in Y-bearing sperm, providing a potential hydrodynamic basis for the altered motility. This reinforces a growing body of work indicating that sperm haploid selection is an important and underappreciated evolutionary force. ER -