Characterization of the gene encoding both growth hormone-releasing hormone (GRF) and pituitary adenylate cyclase-activating polypeptide (PACAP) in the zebrafish.

The purpose of this research was to isolate and characterize the gene encoding growth hormone-releasing hormone (GRF) and pituitary adenylate cyclase-activating polypeptide (PACAP) from the zebrafish. The gene is comprised of five exons with two distinct peptides encoded on separate exons, GRF on exon 4 and PACAP on exon 5. Our evidence indicates that the zebrafish genome contains a single copy of the GRF-PACAP gene. The tissue distribution pattern of the mRNA transcript shows expression in the brain, eye, gastrointestinal tract, ovary and testis; each transcript was sequenced and found to be identical to the gene. This is the first report of GRF-PACAP mRNA expression in the eye of a non-mammalian species. Evidence that a duplication of the PACAP gene gave rise to the vasoactive intestinal peptide (VIP) gene is supported by the high amino acid sequence identity between PACAP in zebrafish and VIP in other fish species.