Cloning, characterization, and tissue distribution of prolactin receptor in the sea bream (Sparus aurata)

The prolactin receptor (PRLR) was cloned and its tissue distribution charac terized in adults of the protandrous hermaphrodite marine teleost, the sea bream (Sparus aurata). An homologous cDNA probe for sea bream PRLR (sbPRLR) was obtained by RT-PCR using gill mRNA. This probe was used to screen inte stine and kidney cDNA libraries from which two overlapping clones (1100 and 2425 bp, respectively) were obtained. These clones had 100% sequence ident ity in the overlapping region (893 bp) and were used to deduce the complete amino acid sequence of sbPRLR. The receptor spans 2640 bp and encodes a pr otein of 537 amino acids. Features characteristic of PRLR, two pairs of cys teines, WS box, hydrophobic transmembrane domain, box 1 and box 2, were ide ntified and showed a high degree of sequence identity to PRLRs from other v ertebrate species. SbPRLR is 29 and 32% identical to tilapia (Oreochromis n iloticus) and goldfish (Carassius auratus) PRLRs, respectively. In the sea bream two PRLR transcripts of 2.8 and 3.2 kb were detected in the intestine , kidney, and gills and a single transcript of 2.8 kb was detected in skin and pituitary by Northern blot. Spermiating gonads (more than 95% male tiss ue; gonado-somatic index of 0.6) contained, in addition to the 2.8-kb trans cript, three more transcripts of 1.9, 1.3, and 1.1 kb. RT-PCR, which is a f ar more sensitive method than Northern blot, detected PRLR mRNA in gills, i ntestine, brain, pituitary, kidney, liver, gonads, spleen, head-kidney, hea rt, muscle, and bone. Immunohistochemistry using specific polyclonal antibo dies raised against an oligopeptide from the extracellular domain of sbPRLR detected PRLR in several epithelial tissues of juvenile sea bream, includi ng the anterior gut, renal tubule, choroid membrane of the third ventricle, saccus vasculosus, branchial chloride cells, and branchial cartilage, (C) 2001 Academic Press.