Cloning and chromosomal localization of a gene encoding a novel serine/threonine kinase belonging to the subfamily of testis-specific kinases

Using reverse transcription-polymerase chain reaction (RT-PCR) with degener ate oligonucleotides corresponding to two highly conserved motifs within th e protein kinase family of catalytic domains, we isolated a PCR fragment en coding a novel member of the testis-specific serine/threonine kinases (STK) from mouse male mixed germ cell mRNA. This PCR fragment recognized a 1020- bp transcript in male germ cells by northern blot analysis and was used to clone a full-length cDNA from a mouse mixed germ cell cDNA library. This cD NA has an open reading frame of 804 bases encoding a protein of 268 amino a cids. This novel gene is almost identical to Stk22c, encoding a recently de scribed testis-specific protein kinase, except for base-pair deletions that result in a shift in the coding region and an alteration of 22 amino acids (residues 109-131). Due to its homology with Stk22c, we have called this p rotein kinase gene Stk22d. Northern blot analysis revealed that this protei n kinase is developmentally expressed in testicular germ cells and is not p resent in brain, ovary, kidney, liver, or early embryonic cells. We then cl oned the human homologue of this protein kinase gene (STK22C) and found it to be expressed exclusively in the testis. Fluorescence in situ hybridizati on with both the human and mouse cDNA clones revealed syntenic localization on chromosomes 1p34-p35 and 4E1, respectively.