The follicle-stimulating hormone β-subunit gene of the common brushtail possum (Trichosurus vulpecula): analysis of cDNA sequence and expression

Reverse transcription–PCR has been used to obtain a cDNA sequence from the follicle-stimulating hormone (FSH) β-subunit gene of the Australian brushtail possum (Trichosurus vulpecula). Comparisons of the possum FSHβ-mRNA coding region nucleotide sequence with that of six eutherian mammal homologues reveals a mean percent identity of 77·3% and 76·8% at the nucleotide and predicted amino acid-sequence levels respectively. Furthermore, the predicted amino acid sequence of the possum FSHβ mature protein shows evolutionary conservation of twelve cysteine residues and two potential N-linked glycosylation sites. The protein lacks the CAGY motif present in most reported glycoprotein β-subunit sequences. The translation termination codon and consensus polyadenylation sequence overlap, a feature observed in other mammalian FSHβ genes. Northern hybridization of total RNA from adult female possum pituitary revealed three hybridizing transcripts of approximately 2·8, 1·2 and 0·5 kb which may arise from utilizing alternative polyadenylation signals. In situ hybridization localized the FSHβ transcripts to a sub-population of anterior pituitary cells interpreted as being gonadotropes. In summary the results indicate considerable evolutionary conservation of the structure of the FSH b-subunit gene between the marsupial and eutherian mammalian lineages.