Spermatogenesis revisited. III. The course of spermatogenesis in a male-sterile pink-eyed mutant type in the mouse

Abstract

Male mice homozygous for the recessive p-locus allele ps are sterile. Spermatogenesis is normal through the completion of meiosis, but is abnormal from the Golgi phase of spermiogenesis on. During acrosome formation various abnormalities appear, ranging from atypical Golgiacrosome complexes to multiple acrosome "implantation" sites on the spermatid nuclei. In many developing acrosomal caps the distribution of acrosomal material is irregular. During the nuclear elongation phase, bundles of microtubules oriented parallel to the manchette have been seen lying in cylindrical invaginations of some spermatid nuclei. In later spermatids, chromatin condensation appears to proceed normally but may be unduly delayed in reaching completion. These various perturbations give rise to a wide spectrum of abnormal spermatozoa ranging from spermatozoa with heads of near-normal morphology to highly bizarre heads which have lost their chromatin. Sperm flagellar ultrastructure is normal and all sperm tails; even those devoid of recognizable heads, are highly motile. These findings support the view that the development of the sperm head is under the control of a group of genes distinct from those mediating events involved in flagella development.

PIP: Sterile male mice, homozygous for the recessive p-locus allende p s were used. Wild-type and mutant littermates were sacrificed at 10 spaced intervals over a 6-20 week period after birth. Tissues were removed and prepared for light and electron microscopy. A minimum of 1000 cells for at least 3 animals of each genotype were observed. The course of spermatogenesis appeared to be normal until the completion of meiosis. During the Golgi phase ultrastructural appearances differed. In mutants spermatids with normal appearing ultrastructure were seen, but the Golgi apparatus frequently appeared less well organized and sometimes more than 1 proacrosome was present, or more than 1 specialized site. Other defects were also seen in older spermatids. Head morphology often showed blebbing and many were highly bizarre. Some spermatozoa were undergoing degeneration and phagocytosis. Flagella development and ultrastructure were normal. Dissociated axonemes and midpieces were common, as were flagella without heads. Multinucleated spermatids were frequently present. Sperm motility was high. Headless spermatozoa were most active. Photographic reproductions illustrate the electron microscopic findings. Since flagella did not show any ultrastructural defects it is concluded that the action of the p s mutant allele was confined to the Golgi-nucelus complex. Therefore the development of the sperm head is probably under a group of genes different from those of the flagella.