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 retin ol-induced cDNAs from rat testis, vitamin A-deficient (VAD) rats were treated with retinol for 4 h and mRNA isolated from their testes was u sed to construct a subtractive cDNA library. One cDNA isolated from th is library contained a sequence for triosephosphate isomerase (TPI). N orthern blot analysis showed that the TPI cDNA hybridized with two tra nscripts in testis. A 1.4-kb transcript, which is the sole transcript found in most tissues, was expressed in the somatic cells of testis, w hereas a novel 1.5-kb transcript was detected only in haploid spermati ds. However, only the level of the shorter transcript increased with r etinol treatment of the testis or of cultured Sertoli cells. Furthermo re, screening of an adult rat testis cDNA library with the TPI cDNA yi elded a cDNA putatively corresponding to the 1.5-kb transcript. Sequen ce analyses of the two TPI cDNAs revealed a 100-bp deletion in one cDN A that may be due to use of an alternative polyadenylation signal. The se results suggest independent processing mechanisms for TPI expressio n in the somatic cells and the haploid germ cells of testis.