Two cDNAs sequences (1320 bp and 1180 bp) of the 55-kDa subunit associated with a testis-specific serine/threonine protein phosphatase 1gamma2 (PP1gamma2) were cloned. They were the same up to 1180 bp, suggesting that they may be generated by alternative splicing. Sequence studies showed that the 1320 bp-cDNA is a homolog of the human sds22alpha(1) (thus, named rat sds22alpha(1)). The 1180 bp-cDNA is a new splice-variant since its sequence at the 3' end has not been identified in human sds22 genes (named rat sds22alpha(3)). The 1320 bp-cDNA is ubiquitously expressed in various tissues including the immature testis. However, the expression of 1180 bp-cDNA was only observed in the testis after puberty. This expression pattern matches very well with that of PP1gamma2, suggesting that 1180 bp-cDNA may encode the 55-kDa subunit to associate with PP1gamma2 in rat testis and is involved in spermatogenesis by controlling PP1gamma2 activity.