Novel alternatively spliced mRNA (1c) of the protein kinase A RI alpha subunit is implicated in haploid germ cell specific expression

By using 5' RACE on rat testis cDNA we identified three alternatively splic ed mRNAs of the Rl alpha subunit of cAMP-dependent protein kinase that diff ered in their 5' untranslated regions. Two of these 5'-regions showed simil arity with the human Rl alpha exons 1a and 1b, while the third (1c) constit uted a novel mRNA splice variant. Northern blot analysis showed that the 1c mRNA was specifically expressed in testis and only in postmeiotic germ cel ls. In contrast, the Rl alpha 1b and Rl alpha 1a mRNAs were present both in premeiotic germ cells and somatic cells of the testis, and the expression of both Rl alpha 1a and 1b mRNAs were stimulated by cAMP in Sertoli cells. In sperm, the Rl alpha protein was expressed after meiosis, and targeted to various subcellular structures via anchoring proteins. The Rl alpha 1c hap loid-specific mRNA, therefore, may be important for the regulation of Rl al pha expression in sperm. Mol. Reprod. Dev. 59:11-16, 2001. (C) 2001 Wiley-L iss, Inc.