RDH10 is Necessary for Initial Vagal Neural Crest Cell Contribution to Embryonic Gastrointestinal Tract Development

Abstract

Retinol dehydrogenase 10 (RDH10) catalyzes the first oxidative step in the metabolism of vitamin A to its active form retinoic acid (RA). Insufficient or excess RA can result in various congenital abnormalities, such as Hirschsprung disease (HSCR). In HSCR, neurons are absent from variable lengths of the gastrointestinal tract due to a failure of neural crest cell (NCC) colonization or development, leading to megacolon and/or the failure to pass meconium. Enteric neurons are derived from neural crest cells (NCC); hence HSCR is associated with incomplete NCC development or colonization of the GI tract. We investigated our hypothesis that RDH10 is necessary for proper NCC contribution to the enteric nervous system (ENS). The mouse point mutant Rdh10trex/trex exhibits decreased retinoid signaling and colonic aganglionosis. Organ explant culture and in utero retinal supplementation experiments define a temporal requirement for RA in ENS development between E7.5-E9.5. Tamoxifen-inducible temporal deletion of RDH10 at E6.5-E7.5 confirms this early retinal role, while later RDH10 deletion suggests retinal independence for continued enteric NCC colonization. Removing RDH10 from NCCs shows no gross or ENS-specific neuronal defects, suggesting that RDH10 is not intrinsically required in enteric NCCs for proper colonization of the gut, but rather is necessary as a paracrine signal in the vagal NCC microenvironment. We investigated signaling cascades that are known to play a role in gut microenvironment maintenance that may be altered in these RDH10 mutants using both a targeted expression analysis approach as well as RNA-sequencing. Candidates include GDNF and its signaling family members such as RET and GFRα1, as well as extracellular matrix proteins. Novel models of HSCR, such as Rdh10trex/trex will improve our understanding of RA contribution to intestinal development and may lead to innovative non-surgical treatment approaches to reduce the morbidity and mortality of this common congenital disease.