Cytoplasmic liberation of protein gene product 9.5 during the seasonal regulation of spermatogenesis in the monkey (Macaca fuscata)

Primate spermatogenesis is distinguished by yet unidentified mechanisms to regulate its spermatogenetic activity. In contrast to the well documented h ormonal regulators, the cellular events responsible for the regulation of t he spermatogenesis has not been addressed. By using PGP 9.5-immunohistochem istry, our previous study demonstrated that the monkey spermatogonia are di vided into two distinct sub-populations, i.e. cytoplasmic PGP 9.5-positive and cytoplasmic PGP 9.5-negative spermatogonia. By comparing the cytoplasmi c expression of PGP 9.5 between the breeding and nonbreeding seasons of the Japanese monkey (Macaca fuscata) in association with PCNA labeling, the pr esent study demonstrates that the cytoplasmic PGP 9.5-positive Ap spermatog onia significantly increases when the spermatogenetic activity declines in the nonbreeding season. An ultrastructural subcellular localization of PGP 9.5 suggests that the increase of the cytoplasmic PGP 9.5 expression is due to a liberation of PGP 9.5 molecule from the nucleus into the cytoplasm. T he results provide a theoretical basis by which PGP 9.5 serves as a novel m arker for spermatogonial subtypes, which will have further implications for future studies on spermatogenesis. The analysis using this novel marker su ggests that the Ap spermatogonia is a key stage to regulate the amount of t he sperm produced in response to the hormonal regulators, and the cytoplasm ic liberation of PGP 9.5 may serve as a pivotal phenomenon that enables the fully restorable, transient suppression of spermatogenesis in primate.