Effects of the gene Wh on reproduction in the Syrian hamster, Mesocricetus auratus.

The gene Wh, causing anophthalmia in the Syrian hamster, Mesocricetus auratus, is a highly pleiotropic gene, which has profound effects upon eye development, pigmentation, and reproduction. Since male hamsters homozygous for this gene are usually sterile, the objective of this study was to determine whether the testes of mutant hamsters differed from the normal phenotype. Accordingly, the testicular tissue from ten normal, ten heterozygous, and ten homozygous mutant animals in the AN/As-Wh strain were compared at the gross, light, and electron microscopic level. Testicular tissue from several mutant animals approached the normal phenotype, due to variable expression of the gene. However, most testes from homozygous mutant hamsters were hypoplastic and aspermic. Abnormalities were observed in Leydig cells, Sertoli cells, and in the developing germ cells. Seminiferous tubules contained germinal epithelium arrested in the early spermatid stage of spermiogenesis, possibly due to premature failure of the Golgi apparatus and subsequent dysgenesis of the acrosome. Since the primary action of the gene is unknown, it was postulated that the gene either acts directly to alter pituitary function, or that the abnormalities in reproduction are due to a failure of eye development and subsequent lack of function of the visual pathway.