MELANOTROPIN AND CORTICOTROPIN ARE ENCODED ON 2 DISTINCT GENES IN THELAMPREY, THE EARLIEST EVOLVED EXTANT VERTEBRATE

In the lamprey, which is a member of the oldest extant class of verteb rates, the agnathans, melanotropins (MSH) and corticotropin (ACTH) wer e found to be encoded on two distinct genes. In all other vertebrates, a single precursor gene, proopiomelanocortin (POMC), encodes MSH and ACTH, as well as beta-endorphin (END). Two different cDNAs were cloned from a lamprey pituitary lambda gt11 cDNA library using antisera agai nst lamprey MSH-B and ACTH(1-16). One cDNA encoded MSH-B, MSH-A and be ta-END, while the other cDNA encoded nasohypophysial factor (NHF), ACT H and a different beta-END, but not MSH-A and MSH-B. Northern blot ana lysis demonstrated that in the adult lamprey pituitary, genes for MSH and ACTH are expressed in the pars intermedia (PI) and pars distalis ( PD), respectively. (C) 1995 Academic Press, Inc.