Male Reproductive Tract

Testis-Specific Expression of Rat Mitochondrial Glycerol-3-Phosphate Dehydrogenase in Haploid Male Germ Cells

Abstract

Mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) is regulated by multiple promoters in a tissue-specific manner. Here, we characterized the testis-specific promoter C of the mGPDH gene and investigated the cellular localization of mGPDH within the testis. Electrophoretic mobility shift experiments identified a cAMP-response element (CRE) site at -57, that was active in the testis. An in vitro translated cAMP-response element modulator (CREM) protein was able to bind this CRE site and an anti-CREM antibody interfered with this complex. Ectopic expression of the testis-specific transcriptional activator CREMtau and protein kinase A in human hepatocarcinoma HepG2 cells activated a promoter C-driven luciferase construct in transient transfection experiments. Furthermore, mGPDH expression was undetectable in testis of CREM-deficient mice. The cellular localization of mGPDH expression and translation in adult rat testis was determined by in situ hybridization and immunohistochemistry techniques. mGPDH transcripts were detected solely in post-meiotic germ cells. Expression of mGPDH was restricted from round spermatids to early elongating spermatids. mGPDH protein was detected delayed in post-meiotic germ cells, restricted from late elongating spermatids to mature spermatids. Our results indicate that rat mGPDH is expressed by a testis-specific promoter from haploid male germ cells in a stage-specific manner.