Sequence and expression analyses of cholecystokinin (CCK) precursor cDNA in the Japanese flounder (Paralichthys olivaceus)

A cholecystokinin (CCK) precursor cDNA was identified from the brain of Jap anese flounder (Paralichthys olivaceus). The full open reading frame was ob tained by a combination of 3' and 5' RACE amplifications and encodes the 13 6 amino acid precursor. The Japanese flounder CCK-8 amino acid sequence was shown to be Asp-Tyr-Leu-Gly-Trp-Met-Asp-Phe, in which the methionine in th e third position of mammalian and amphibian CCK-8 was replaced with leucine , similar to what has been shown in the goldfish. By RT-PCR, expression of CCK precursor mRNA was detected from the brain, stomach and proximal intest ine. Whole mount in situ hybridization detected CCK mRNA in scattered cells in the proximal intestine epithelium as well as cerebrum of brain, suggest ing the central nervous system and digestive system express the same CCK pr ecursor mRNA.