Mouse homologues of the human AZF candidate gene RBM are expressed in spermatogonia and spermatids, and map to a Y chromosome deletion interval associated with a high incidence of sperm abnormalities

An RNA-binding motif (RBM) gene family has been identified on the human Ychromosome that maps to the same deletion interval as the 'azoospermiafactor' (AZF). We have identified the homologous gene family (Rbm) on themouse Y with a view to investigating the proposal that this gene familyplays a role in spermatogenesis. At least 25 and probably >50 copies ofRbm are present on the mouse Y chromosome short arm located between Sry andthe centromere. As in the human, a role in spermatogenesis is indicated bya germ cell-specific pattern of expression in the testis, but there aredistinct differences in the pattern of expression between the two species.Mice carrying the deletion Yd1, that maps to the proximal Y short arm, arefemale due to a position effect resulting in non-expression of Sry ;sex-reversing such mice with an Sry transgene produces males with a highincidence of abnormal sperm, making this the third deletion interval on themouse Y that affects some aspect of spermatogenesis. Most of the copies ofRbm map to this deletion interval, and the Yd1males have markedly reducedRbm expression, suggesting that RBM deficiency may be responsible for, orcontribute to, the abnormal sperm development. In man, deletion of thefunctional copies of RBM is associated with meiotic arrest rather thansperm anomalies; however, the different effects of deletion are consistentwith the differences in expression between the two species.