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

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 ß-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.

Spatial and temporal expression profiles of urocortin 3 mRNA in the brain of the chicken (Gallus gallus).

Urocortin 3 (UCN3) is a neuropeptide believed to regulate stress-coping responses by binding to type 2 corticotropin-releasing hormone receptors. Here, we report the cloning and brain distribution of UCN3 mRNA in a sauropsid-the chicken, Gallus gallus. Mature chicken UCN3 is predicted to be a 40-amino acid peptide showing high sequence similarity to human (93%), mouse (93%), and Xenopus (88%) UCN3. During the last third of embryonic development, UCN3 mRNA levels changed differentially in the various brain parts. In all brain parts, UCN3 mRNA levels tended to increase toward hatching, except for caudal brainstem, where a gradual decrease was observed during the last week of embryonic development. In cerebellum, a rapid increase in gene expression occurred between embryonic days 17 and 19. Using in situ hybridization, UCN3 mRNA was found to be expressed predominantly in the hypothalamus, pons, and medulla of posthatch chick brains, but not in some areas that are among the main expression sites in rodents, such as the brain areas where in mammals the median preoptic nucleus and the medial amygdala are located. This suggests that the roles of UCN3 in chicken, and perhaps sauropsids in general, are not all identical to those in rodents.