cDNA sequence analysis, gene expression and protein localisation of the inhibin alpha-subunit of Australian brushtail possum (Trichosurus vulpecula)

Abstract

An inhibin -subunit cDNA sequence from the Australian brushtail possum (Trichosurus vulpecula) has been identified and analysed. The cDNA includes an open reading frame encoding a predicted precursor protein of 361 amino acids. The predicted protein sequence includes four possible proteolytic cleavage sites, 12 evolutionarily conserved cysteine residues and three potential N-linked glycosylation sites. The mature -subunit is the carboxyl terminal fragment ( C) consisting of 131 amino acids. The full-length precursor protein shows a mean identity with eutherian homologues of 69·8%. The homology is not evenly distributed, with the putative C fragment showing the highest level (79·7%). Using Northern hybridisation, an -subunit transcript of approximately 1·6 kb was detected in adult possum ovary. Using in situ hybridisation and immunocytochemistry, inhibin -subunit was localised exclusively to the granulosa cell layers of follicles. Hybridisation and immunostaining for the inhibin -subunit were first observed in granulosa cells of primary follicles and the expression continued throughout all stages of follicular growth. Inhibin -subunit mRNA and protein were also detected in cells of the corpus luteum. In summary, results indicate considerable conservation of the structure and possible function of the inhibin -subunit protein since the divergence of the marsupial and eutherian mammalian lineages. The expression data suggest that, in the adult possum, inhibin may have a role in ovarian follicular growth from the primary stage of development.

Activin, Inhibin, and Follistatin in Zebrafish Ovary: Expression and Role in Oocyte Maturation1

“…Molecular cloning and immunological studies in a variety of animals reveal that these forms of activin may be also present in other lower vertebrates. However, cDNA for ␣ subunit has been cloned from only several mammals [9][10][11][12][13][14], and chickens [15], but not from lower vertebrates.…”