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

Abstract

Reverse transcription-PCR has been used to obtain a cDNA sequence fromthe follicle-stimulating hormone (FSH) β-subunit gene of the Australianbrushtail possum (Trichosurus vulpecula). Comparisons ofthe possum FSHβ-mRNA coding region nucleotide sequence with that of sixeutherian mammal homologues reveals a mean percent identity of77·3% and 76·8% at the nucleotide and predictedamino acid-sequence levels respectively. Furthermore, the predicted amino acidsequence of the possum FSHβ mature protein shows evolutionary conservationof twelve cysteine residues and two potential N-linkedglycosylation sites. The protein lacks the CAGY motif present in most reportedglycoprotein β-subunit sequences. The translation termination codon andconsensus polyadenylation sequence overlap, a feature observed in othermammalian FSHβ genes. Northern hybridization of total RNA from adultfemale possum pituitary revealed three hybridizing transcripts ofapproximately 2·8, 1·2 and 0·5 kb which may arise fromutilizing alternative polyadenylation signals. In situhybridization localized the FSHβ transcripts to a sub-population ofanterior pituitary cells interpreted as being gonadotropes. In summary theresults indicate considerable evolutionary conservation of the structure ofthe FSH b-subunit gene between the marsupial and eutherian mammalian lineages.