Avian galanin: cloning of complementary DNAs and characterization of transcripts in different tissues

Avian galanin was first isolated from the chicken intestine, and subsequently from the quail oviduct. Avian galanin is a 29-residue peptide including an amidated threonine at the C-terminus and differs at several positions from the C-terminal part of mammalian galanins. In contrast to extensive mammalian studies, no information is available on the structure of precursor molecule of avian galanin. In this study, therefore, we conducted complementary DNA (cDNA) cloning of the avian galanin gene from quail brain RNA using degenerated 3'RACE and 5'RACE techniques. A cloned cDNA for avian galanin contained an open reading frame consisting of 117 amino acids which had overall amino acid homology of 63%, 60%, 54%, 58%, and 62% with bovine, human, mouse, porcine, and rat galanins, respectively. Another cDNA containing a 69-nucleotide insertion, which gave an additional 23 amino acids to mature avian galanin, was also cloned, suggesting the presence of two transcripts by alternative splicing. Northern blot analysis revealed that avian galanin mRNA was expressed, as a shorter transcript, in the quail brain, ovary, and intestine, unlike the liver and oviduct. A larger mRNA of avian galanin may be further expressed only in the ovary.