Testis Specific Serine Kinase 3 (TSSK3)

Using degenerate primers corresponding to 2 highly conserved protein kinase motifs, Visconti et al. (2001) cloned mouse Stk22d by PCR. Using this sequence as query, they identified an EST containing the human homolog of Stk22d, STK22C, and they obtained the full-length cDNA by 3-prime and 5-prime RACE of a testis cDNA library.

The mouse and human proteins contain 268 amino acids and share 100% amino acid homology. Northern blot analysis of 8 human tissues detected transcripts of 1.0 and 1.35 kb only in testis. Transcription of Stk22d in mouse testis began 20 to 24 days after birth. In adult mouse testis, expression was detected in round and condensing spermatids, but not in meiotic pachytene spermatocytes.