Nuclear localization of huntingtin during spermatogenesis.

Huntingtin is a ubiquitous cytoplasmic protein. Mutant huntingtin causes Huntington's disease and its intranuclear inclusion is associated with cytotoxicity. Nuclear localization of normal huntingtin is detected in the oocyte up to 2.5 days post coitum. Therefore, huntingtin is expected to reside in the nucleus even before fertilization. The present study determined normal huntingtin distribution during spermatogenesis. Testicles from an adult male Sprague-Dawley rat were stained with anti-huntingtin antibody and nuclear counterstaining was performed with 4',6-diamidino-2-phenylindole. Concerning nuclear localization, huntingtin was detected in the spermatids, whereas predominant cytoplasmic localization of it was evident in the spermatogonia. Between the primary and secondary spermatocytes, huntingtin appeared to be delocalized in the nuclei when meiosis occurred. The findings provide evidence that normal huntingtin is transported to the nuclear compartment during the meiotic stage of spermatogenesis.