Here we report the cloning and characterization of a novel cDNA named spata 2. SPATA2 is the ortholog of PD1, a human testicular protein which has been suggested to play a role in spermatogenesis. The spata 2 sequence reveals an open reading frame encoding a protein of 511 amino acids. Northern blot analysis with rat mRNA demonstrated two distinct transcripts of 2.2 and 4.0 kb. Tagging recombinant SPATA2 with the green fluorescent protein (GFP) and expressing the chimeric polypeptide in HLtat transfected cells indicated that SPATA2 is located in the nucleus. RT-PCR analysis revealed that spata 2 mRNA is expressed in the testis and to a lesser extent in the brain while skeletal muscle and kidney showed a barely visible signal. The same analysis demonstrated that isolated Sertoli cells express spata 2 mRNA. Treating Sertoli cells with. FSH in vitro induced remarkable changes in the steady-state level of spata 2 mRNA in a time-dependent manner. In developing testis spata 2 transcripts were first detected 10 days post partum and expression levels increased steadily with age. The ability of FSH to stimulate spata 2 mRNA expression as well as its developmental expression suggests that this protein might play a role in regulating spermatogenesis and thus, according to the Gene Nomenclature Committee, we propose the name SPATA2 (Spermatogenesis associated protein 2) for this protein (or gene).