A Transgenic Analysis of Mouse Lactate Dehydrogenase c Promoter Activity in the Testis

Transcription of the mouse testis-specific lactate dehydrogenase c (mldhc) gene is limited to cells of the germinal epithelium. Cloning and analysis of the mldhc promoter revealed that a 100-bp core promoter was able to regulate testis-specific transcription in vitro and in transgenic mice. Surprisingly, expression of the reporter in transgenic testes was limited to pachytene spermatocytes, whereas native LDH-C₄ was detected in pachytene and all later germ cells. To locate additional regulatory sequence that could recapitulate the native LDH-C₄ distribution pattern, we investigated the contribution of 5′ and 3′ flanking sequences to the regulation of LDH-C₄ expression. We found that transcription factor YY1 binds to the mldhc promoter, that the mldhc 3′ untranslated sequence does not permit a postmeiotic expression of a β-galactosidase reporter in transgenic mice, and that native mldhc mRNA is predominately meiotic, with only a low level of postmeiotic distribution. Our results suggest that the high level of LDH-C₄ in postmeiotic cells results from mRNA and protein stability.