Expression analysis of the regenerating gene (Reg) family members Reg-IIIβ and Reg-IIIγ in the mouse during development

The regenerating gene/regenerating islet-derived (Reg) family is a group of small secretory proteins. Within this family, Reg type-III (Reg-III) consists of: Reg-III alpha, -beta, -gamma, and -delta. To elucidate the physiological relevance of Reg-III, we examined the localization and ontogeny of Reg-III beta and Reg-III gamma in mice at different time points spanning from embryonic day 13.5 to 7 weeks old, using in situ hybridization and immunohistochemistry. Our results showed that Reg-III beta was expressed in specific subsets of primary sensory neurons and motor neurons, and that expression was transient during the embryonic and perinatal periods. Reg-III beta expression was also observed in absorptive epithelial cells of the intestine. In contrast, Reg-III gamma expression was mainly observed in epithelial cells of the airways and intestine, but not in the nervous system, and expression levels showed a gradually increasing pattern along with development. In the airways Reg-III gamma was expressed in goblet and Clara-like cells, whereas in the intestine Reg-III gamma was expressed in the absorptive epithelial cells and Paneth cells, and was found to be expressed in development before these organs had been exposed to the outside world. The present findings imply that Reg-III beta and Reg-III gamma expression is regulated along divergent pathways. Furthermore, we also suggest that expression of Reg-III gamma in the airway and intestinal epithelia may occur to protect these organs from exposure to antigens or other factors (e.g., microbes) in the outer world, whereas the transient expression of Reg-III beta in the nervous system may be associated with the development of the peripheral nervous system including such processes as myelination. J. Comp. Neurol., 2012;520:479494. (C) 2011 Wiley Periodicals, Inc.