The evidence for post-meiotic expression of a testis-specific isoform of a regulatory subunit of calcineurin using a monoclonal antibody

The expression of a regulatory subunit of calcineurin (CaNβ) during rat spermatogenesis was examined in rat testes using a monoclonal antibody Val. Results showed that a testis-specific isoform of CaNβ was expressed only 3 weeks after birth, when meiosis begins, and increased in amount depending on the maturation of spermatogenesis. The matured sperm, which consists of only post-meiotic cells, is most likely to have only the testis-specific isoform of CaNβ. The brain type isoform of CaNβ was not detected in rat sperm. Immunoblot analysis of testes from different rodent species by a monoclonal antibody Val showed that all rodent species examined had their own homologues corresponding to a testis-specific isoform of CaNβ in rats, although they showed distinctively different molecular weights on SDS-PAGE compared to the testis-specific isoform in rats. Each homologue was shown to be specifically expressed in postmeiotic phase of spermatogenesis, as was seen in rats.