Expression of triosephosphate isomerase transcripts in rat testis: evidence for retinol regulation and a novel germ cell transcript.

Vitamin A is essential for mammalian spermatogenesis. To isolate retinol-induced cDNAs from rat testis, vitamin A-deficient (VAD) rats were treated with retinol for 4 h and mRNA isolated from their testes was used to construct a subtractive cDNA library. One cDNA isolated from this library contained a sequence for triosephosphate isomerase (TPI). Northern blot analysis showed that the TPI cDNA hybridized with two transcripts in testis. A 1.4-kb transcript, which is the sole transcript found in most tissues, was expressed in the somatic cells of testis, whereas a novel 1.5-kb transcript was detected only in haploid spermatids. However, only the level of the shorter transcript increased with retinol treatment of the testis or of cultured Sertoli cells. Furthermore, screening of an adult rat testis cDNA library with the TPI cDNA yielded a cDNA putatively corresponding to the 1.5-kb transcript. Sequence analyses of the two TPI cDNAs revealed a 100-bp deletion in one cDNA that may be due to use of an alternative polyadenylation signal. These results suggest independent processing mechanisms for TPI expression in the somatic cells and the haploid germ cells of testis.