Molecular cloning of cDNA encoding two types of pituitary gonadotropin alpha subunit from the goldfish, Carassius auratus.

Two types of cDNA encoding the alpha subunit of pituitary gonadotropin (GTH) were cloned by polymerase chain reaction (PCR) for goldfish pituitary cDNA library. The goldfish GTH-alpha subunit cDNAs, designated as alpha 1 and alpha 2, encode 117 and 118 amino acids, respectively, including a 23-amino-acid signal peptide. These two types of cDNAs showed high homology in nucleotide and amino acid sequence, but deletion of a triplet nucleotides was present in alpha 1. Deduced amino acid sequences represented differences in four residues between alpha 1 and alpha 2 subunits. Analyses of goldfish genomic DNA revealed that each individual goldfish possesses two distinct genes relevant to GTH-alpha 1 and -alpha 2 subunits. Results of reverse transcriptase-PCR analysis suggest that these two GTH-alpha subunit genes are expressed at different levels without relation to sex and gonadal maturity.