Centrosome Reduction during Mouse Spermiogenesis

The sperm does not contribute the centrosome during murine fertilization. To determine the manner in which a functional centrosome is reduced, we have studied centrosome degeneration during spermiogenesis of mice. The round spermatids display normal centrosomes consisting of a pair of centrioles along with γ-tubulin containing foci. However, they do not seem to organize microtubules. Elongating spermatids display γ-tubulin spots in the neck region, while microtubules are organized from the perinuclear ring as the manchette. Electron microscopic studies using immunogold labeling revealed that γ-tubulin is mainly localized in the centriolar adjunct from which an aster of microtubules emanates. Microtubules repolymerized randomly in the cytoplasm after nocodazole treatment and reversal. γ-Tubulin dissociates from the neck region and is discarded in the residual bodies during spermiation. The distal centriole degenerates during testicular stage of spermiogenesis, while the proximal centriole is lost during epididymal stage. Loss of centrosomal protein and centrioles in mouse sperm further confirm the maternal inheritance of centrosome during murine fertilization.