CHARACTERIZATION OF THE CHICKEN PREPROGONADOTROPHIN-RELEASING HORMONE-I GENE

Partial cDNA clones for chicken gonadotrophin-releasing hormone (GnRH) -I were isolated by reverse transcription-polymerase chain reaction us ing total RNA from the hypothalami of domestic chickens. Primers for a mplification were based on the nucleotide sequence of the mammalian Gn RH genes. These amplified clones were used to screen a genomic library from which a series of overlapping clones was isolated. A 6.3 kb EcoR I fragment containing all the exons and 3.0 kb of the 5' upstream regi on was sequenced. The exon-intron structure of the gene was found to b e of a similar configuration to those of the mammalian and osteichthye s GnRH genes analysed so far. Individual domains of the predicted prep ropeptide are similar to those of mammalian GnRH prepropeptides, compr ising a 23 amino acid signal peptide, the decapeptide hormone and a Gl y-Lys-Arg cleavage site, followed by a 56 amino acid GnRH-associated p eptide. The nucleotide sequence coding for the decapeptide hormone tra nslates into the amino sequence for chicken GnRH-I. The prepropeptide has approximately 50% identity with mammalian prepropeptides and 25% i dentity with the teleost prepropeptides.