Expression of the proopiomelanoco regulated and affected by germ cel reproductive system (testis/gene expression/cellular interactions/opioid peptides/paracr

Proopiomelanocortin (POMC), a major pitu- itary product, is also present in the adult mouse testis. We have shown previously that POMC mRNAs are most abundant in a subpopulation of Leydig cells associated with tubules in specific stages of the cycle of the seminiferous epithelium. In the present study, we examined the expression of the gene encoding POMC during testicular development and in other tissues of the male reproductive system. We also analyzed the effects of cellular interactions on POMC gene expression in the testis. Blot- hybridization analysis revealed that POMC transcripts of -800 nucleotides were present in enriched populations of meiotic prophase spermatocytes and in caput epididymis but were absent in cauda epididymis and vas deferens. POMC tran- scripts were present in fetal testis (day 17 of gestation to newborn), could not be detected in prepuberal testis (days 7-8 postpartum), but reappeared in the adult testis. No difference in the size or abundance of POMC transcripts was seen in testes from mouse mutant strains in which spermatogenesis is arrest- ed in early spermiogenesis. In contrast, POMC transcripts were virtually undetectable in testes that are devoid of germ cells. These results emphasize the importance of interactions between germ cells and interstitial cells and the regulation of the POMC gene in the mammalian testis.