Cloning, sequence characterization, and expression patterns of members of the porcine TSSK family

Testis-specific serine kinases (TSSKs) are a family of serine/threonine kinases highly expressed in the testes that are responsible for regulating many spermatogenesis-related protein activities. Mutations in this family have a positive relationship with oligospermia and azoospermia in human and mouse. Here, five members of the TSSK family from a Banna mini-pig inbred line (BMI) were cloned, sequenced, and characterized. The full-length coding sequences of BMI TSSKs varied from 807 (TSSK3) to 1095 bp (TSSK1) and encoded 268 to 364 amino acids with molecular weights in the range 30.11 to 41.34 kDa. Following comparison with TSSK4 genes in other species, BMI TSSK4 was found to contain three alternatively spliced variants, inform1, inform 3, and inform 4. BMI TSSK1 and TSSK2 are co-localized on the Sus scrofa chromosome (SSC) 14, and consist of a single exon; TSSK3, TSSK4, and TSSK6 are on SSC6, SSC7, and SSC2, and consist of two, four, and one exon, respectively. Multiple protein sequence alignment and phylogenetic analysis showed that the regions spanning the S_TKc domains were more conserved between pig and other animals: with TSSK1 and TSSK2 and TSSK3 and TSSK6 displaying the greatest degree of homology across species, and the TSSK4 protein clearly distinct from other members. Multi-tissue RT-PCR showed BMI TSSK1, TSSK3, and TSSK4 were only expressed in the testes and seminal vesicle, TSSK2 was confined to testes only, while TSSK6 was expressed widely in adult tissues but was highest in the testes.