Cloning, expression, and tissue localisation of prolactin in adult sea bream (Sparus aurata)

A major action of prolactin (PRL) in teleost fish is the maintenance of hyd romineral balance in euryhaline species in fresh water. The function of PRL in marine teleosts is less certain and unlike euryhaline teleosts, such as tilapia and salmon, there is relatively little information about protein o r gene structure. Associated with studies to determine potential functions of PRL, pituitary prolactin cDNA has been cloned and sequenced from sea bre am (Sparus aurata), a marine teleost. The sequence obtained spanned 1349 bp and contained an open reading frame encoding a protein of 212 amino acids composed of a putative signal peptide of 24 residues and a mature protein o f 188 amino acids. N-terminal sequencing of the native protein confirmed un ambiguously the cleavage site, Ala(24), Val(25), predicted from alignments of the sea bream PRL cDNA with that of other teleosts. The presence of only one form of PRL in sea bream was supported by identification using Norther n blots of only a single transcript of 1.35 kb. Reverse transcription and p olymerase chain reaction techniques coupled with Southern blot analysis res ulted in the detection of PRL in the pituitary but also in the intestine, l iver, ovary, and testes. (C) 1999 Academic Press.