Novel Vasopressin Gene-Related Transcripts in Rat Testis

Abstract

Although the arginine vasopressin (AVP) gene is predominantly expressed in specific hypothalamic neurons, immunoreactive AVP (irAVP) has also been identified in peripheral tissues, including testis. To determine whether hypothalamic and testicular ir-AVPs derive from the same or different transcripts, we examined testicular AVP gene-related transcripts by Northern blot analysis, polymerase chain reaction (PCR), and RNase mapping. We show that the testis contains three distinct AVP gene-related transcripts of 0.67, 0.83, and 2.0 kilobases (kb) which differ in size from the 0.81-kb hypothalamic AVP mRNA. As demonstrated by deadenylation, this size heterogeneity is not due to differences in the length of the poly(A) tails. By the use of exon-specific probes we determined that the 0.67- and the 0.83-kb transcripts contain exons B and C, but not A. In contrast, the 2-kb transcript is the only testicular transcript that contains an exon A-related sequence. By application of the PCR technique, we confirm the existence of testicular transcripts in which exons B and C are spliced together, but exon A is excluded. Our findings indicate that the 0.67- and 0.83-kb mRNA results from a differential splicing event that excludes exon A and that the 2-kb mRNA probably originates from the expression of an AVP-related gene. Since the nonapeptide AVP is encoded by exon A, testicular irAVP cannot arise from the translation of any of the exon B- and C-containing transcripts, and any mRNA that has so far been identified by AVP exon C probes is unrelated to the biosynthesis of AVP-immunoreactive products.(ABSTRACT TRUNCATED AT 250 WORDS)