The expression pattern of the pyruvate dehydrogenase E1 alpha subunit genes during spermatogenesis in adult mouse

The expression patterns of the testis-specific and somatic forms of the pyruvate dehydrogenase (PDH) E1 alpha subunit genes were examined in adult mouse testis by in situ hybridization with specific cDNA probes and by immunostaining. A considerable increase in the mRNA level of the testis-specific PDH E1 alpha gene was observed in spermatocytes at the pachytene stage. The expression gradually decreased in spermatids as spermiogenesis progressed (especially after step 11) and it was not detectable in residual bodies. Transcripts of the testis-specific PDH E1 alpha gene were not identified in nongerminal Leydig and Sertoli cells. In contrast, the expression of the somatic form of the PDH E1 alpha gene was detected in spermatogonia, Leydig cells, and Sertoli cells at a low level. Transcripts of the somatic form of the PDH E1 alpha gene were not identified in other types of germ cells in adult mouse testis. Immunostaining with a PDH E1 alpha-specific antibody showed that the synthesis of PDH E1 alpha protein was dramatically increased in primary spermatocytes and that PDH E1 alpha protein existed abundantly in pachytene spermatocytes. The amount of PDH E1 alpha protein remained at a high level throughout spermiogenesis; however, it declined remarkably in epididymal spermatozoa. Leydig cells, Sertoli cells, and spermatogonia had low levels of PDH E1 alpha protein. These results suggest that (1) the transcription switch from the somatic form of the PDH E1 alpha gene to the testis-specific PDH E1 alpha gene occurs during the first meiotic prophase of spermatogenesis in adult mouse testis, and (2) PDH E1 alpha protein coded for by the testis-specific PDH E1 alpha gene is involved in the development of spermatogenic cells especially at stages after first meiotic prophase until the end of spermiogenesis in the testis.