Molecular cloning of proopiomelanocortin cDNA from an elasmobranch, the stingray, Dasyatis akajei

Recently we have characterized a new MSH (named delta-MSH) which joins the group of MSHs (alpha, beta, gamma) in dogfish proopiomelanocortin (POMC). T he present study has confirmed the presence of delta-MSH in POMC of another member of the elasmobranchian order, the stingray, Dasyatis akajei, by cDN A cloning from pituitary mRNAs. Overlapping partial cDNA clones correspondi ng to stingray POMC were amplified by PCR from single-strand cDNA prepared from pituitary poly (A)(+) RNA. Excluding the poly A tail, stingray POMC cD NA consists of 1077 base pairs (bp). It contains a 912-bp open reading fram e encoding a signal peptide of 24 amino acids (aa) and a POMC of 280 aa. ga mma-MSH, alpha-MSH, ACTH, delta-MSH, beta-MSH, and beta-endorphin are locat ed at POMC (50-61), (115-127), (115-153), (182-193), (226-242), and (245-28 0), respectively. The stingray POMC is smaller than that of the dogfish POM C (294 aa) mainly due to the absence of a sequence of 11 consecutive aa bet ween delta-MSH and beta-MSH. delta-MSH has been found only in the elasmobra nchs and, therefore, delta-MSH might have evolved after the divergence of c hondrichthians from the ancestral vertebrate lineage and before divergence of sharks and rays. (C) 2000 Academic Press.