Transcriptional expression of a testis-specific variant of the mouse pyruvate dehydrogenase E1 alpha subunit

An isogene of the E1 alpha subunit of the mouse pyruvate dehydrogenase complex was shown in a previous study to map to chromosome 19. Here we demonstrate using Northern blot analysis that this gene is expressed in a testis-specific fashion. Two testis-specific E1 alpha transcripts were detected: (1) a 2.0-kb transcript that is abundant in pachytene cells but also detectable during earlier stages of spermatogenesis, and (2) a shorter 1.7-kb transcript detectable only in round spermatids. Analysis of both transcripts following RNase H digestion revealed that the smaller message is not derived from the shortening of the poly(A) tail and most likely results from the alternate use of two polyadenylation signals. Finally, analysis of polysomes isolated from 20- and 80-day-old mouse testes demonstrated that the 2.0-kb transcript is associated with the polysomal fraction, suggesting that this message is transcribed and actively translated at the same time. We conclude from these results that expression of the testis-specific E1 alpha is initially expressed during the meiotic prophase stage of spermatogenesis and not under any apparent post-transcriptional regulation.