Influence of partial deletion of the Y chromosome on mouse sperm phenotype.

Two congenic strains of mice (control, B10.BR/SgSn; mutant, B10.BR-Ydel/Ms with partial deletion of the Y chromosome) were examined. In control males, 22.6% of spermatozoa had abnormal heads; in mutant males, there were 64.2%, the most common being heads with flat acrosomes. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of mature sperm proteins, followed by acrosin assay and acrosome silver staining, revealed a reduced concentration of acrosin in acrosomal caps in 35.8% of the spermatozoa in mutant males. Electron microscope analysis showed that some of the round, early spermatids in the mutants had normally formed acrosomal caps but lacked the proacrosomal granule and had no, or only scarce, acrosomal material. These observations indicate that formation of the acrosomal cap is controlled separately from the synthesis of the acrosomal material and suggest that some factors linked on the Y chromosome are involved in the control of acrosome development.