Spermatogenesis involves the processes of germ cell proliferation, meiosis, and maturation. Germ cells at different spermatogenetic developmental stages exist through out the seminiferous tubules. In cross-sections of seminiferous tubules, staging of spermatogenesis is usually performed using PAS-hematoxylin staining, however, most studies also involve immunofluorescence analysis, which can be negatively affected by cell staining. Therefore, finding staging markers compatible with commonly used immunofluorescence techniques could be technically advantageous. In this study rat testis sections were evaluated for immunofluorescence expression profiles of topoisomerase 2α and topoisomerase 2β (Top2α and Top2β). Stage-specific patterns were seen for both proteins. Topoisomerase 2α was present in the nuclei of the spermatocytes from spermatogenesis stages 7 to 14. Alternatively, topoisomerase 2β was present in the nuclei of elongating and condensing spermatids. It was observed initially as 2-4 small foci in spermiogenesis step 2, then as a single focus near the nuclear membrane of round spermatids from spermiogenesis steps 3 to 8. The Top2β foci were distinct from the chromatoid body and proximal to the Golgi apparatus, which is known to be adjacent to the acrosome. Based on these specific findings we propose that the Top2β locates to the acrosome and that Top2α and Top2β immunofluorescence may be useful staging markers.
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