Two cDNAs sequences (1320 bp and 1180 bp) of the 55-kDa subunit associated with a testis-specific serine/ threonine protein phosphatase 1 gamma 2 (PP1 gamma 2) 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 sds22 alpha(1), (thus, named rat sds22 alpha(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 sds22 alpha(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 PP1 gamma 2, suggesting that 1180 bp-cDNA may encode the 55-kDa subunit to associate with PP1 gamma 2 in rat testis and is involved in spermatogenesis by controlling PP1 gamma 2 activity,