Molecular cloning and nucleotide sequence analysis of the putative cDNA for the precursor molecule of the chicken LH-beta subunit.

A cDNA expression library was constructed from poly(A)+ RNA of broiler chicken adenohypophyses using lambda gt11 as a vector. After screening with a rabbit antiserum against chicken LH, a cDNA clone (L12) containing a 436 bp insert was obtained. Using a subclone of L12 in pUC19 (pL12) as the hybridization probe, another cDNA clone (LF127) with a 533 bp insert was isolated. The LF127 contained the full-length cDNA encoding the putative chicken LH-beta subunit precursor molecule. Hybridization of the pL12 cDNA insert to adenohypophysial RNA showed that chicken and Japanese quail adenohypophyses contained RNA species of about 0.8 and 1.0 kb respectively. The amount of this RNA species was ten times higher in adult male quails kept under long days at room temperature than in those kept under short days at 7 degrees C. In situ hybridization experiments showed the exclusive distribution of the signal in the LH cells of the adenohypophysis. The similarity of the nucleotide sequence of the apoprotein-coding region of LH-beta cDNA of the chicken to that of mammals is lower than that among mammals. The deduced amino acid sequence of the chicken LH-beta subunit supports the hypothesis that the number of proline residues increases in the LH-beta subunit the closer phylogenetically the vertebrate is to mammals.