Molecular cloning and tissue distribution of Crh and Pomc mRNA in the fat-tailed dunnart (Sminthopsis crassicaudata), an Australian marsupial

Abstract

Like all vertebrates, marsupials respond to stressors with the activation of the hypothalamo-pituitary-adrenal axis. However, peptides operating at the higher regulatory levels of this hormonal system, i.e. corticotropin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH), have not been investigated in marsupials. Here we report the molecular cloning of the precursor cDNAs of CRH (prepro-CRH) and of ACTH (proopiomelanocortin; POMC) in an Australian marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata). Dunnart POMC and prepro-CRH are predicted to be peptides of 399 and 200 amino acids, respectively. While the ACTH and β-endorphin sequences within the POMC sequence are highly conserved, the POMC sequence shows some unique features in this species, and perhaps all Australian marsupials, including the loss of a γ-melanotropin sequence and duplications of the ACTH sequence. Mature dunnart CRH is identical to CRH in human, mouse, rat and chicken. Pomc and Crh mRNA is mainly expressed in dunnart pituitary gland and brain, respectively, but both are also present in a range of peripheral tissues.