Two salmon gonadotropin-releasing hormone genes and their differential expressions in the goldfish Carassius auratus

A complementary DNA (cDNA) encoding salmon type gonadotropin-releasing horm one (sGnRH) has already been isolated and characterized in the goldfish Car assius auratus. In the present study, we isolated and characterized a secon d sGnRH cDNA which was different from the reported sGnRH cDNA from the brai n of goldfish by rapid amplification of cDNA ends. This cDNA included an op en reading frame of 282 bp encoding the 94 amino acid residues of sGnRH pre cursor. Amino acids identity between the second sGnRH precursor and the pre viously reported sGnRH precursor was 86.2%. Genomic Southern blot analysis showed that the goldfish harbors these two distinct sGnRH genes in its geno me. Expressions of the two sGnRH genes were observed in the brain, pituitar y, and gonad of goldfish by reverse transcription-polymerase chain reaction analysis. Moreover, the levels of two sGnRH mRNA in these tissues were dif ferent depending on sex and maturity of the fish. The differential expressi ons of two sGnRH genes suggest the existence of the differential regulatory mechanism of the two sGnRH genes and the multiple physiological functions of sGnRH.