Nucleotide (cDNA) sequence encoding the horse gonadotrophin α-subunit
ABSTRACT Several cDNA clones corresponding to mRNA for the α-subunit of the horse (Equus caballus) pituitary and placental (chorionic) gonadotrophic hormones have been isolated and sequenced. Polyadenylated mRNA was purified from horse pituitary glands (the source of FSH and LH) and horse placental tissues (the source of chorionic gonadotrophin; CG). The mRNA preparations were characterized by in-vitro translation and Northern hybridization techniques using human and ovine gonadotrophin cDNA clones as probes. Complementary DNA libraries were created from the pituitary and placental mRNAs and a human CG α-subunit probe was used to isolate several horse α-subunit cDNA clones. The α-subunit nucleotide sequence from both sources of tissue was identical, thereby indicating that in the horse (as in man) the same gonadotrophin α-subunit gene is expressed in the pituitary and placenta. Our results are consistent with transcription of a single α-subunit gene for all the glycoprotein hormones in the horse, and we suggest that the reported differences between the horse CG and FSH α-subunit amino acid sequences determined by conventional peptide sequencing methods arose due to errors in the FSH α-subunit sequence. Comparison of the deduced amino acid sequence of the horse α-subunit with that of other α-subunit sequences indicated a number of significant differences which may be related to the unusual receptor-binding properties of the equine gonadotrophins. J. Endocr. (1987) 115, 341–346