Neural crest requires Impdh 2 for development of the enteric nervous system, great vessels, and craniofacial skeleton

Abstract

Mutations that impair the proliferation of enteric neural crest-derived cells (ENCDC) cause Hirschsprung disease, a potentially lethal birth defect where the enteric nervous system (ENS) is absent from distal bowel. Inosine 5′ monophosphate dehydrogenase (IMPDH) activity is essential for de novo GMP synthesis, and chemical inhibition of IMPDH induces Hirschsprung disease-like pathology in mouse models by reducing ENCDC proliferation. Two IMPDH isoforms are ubiquitously expressed in the embryo, but only IMPDH2 is required for life. To further understand the role of IMPDH2 in ENS and neural crest development, we characterized a conditional Impdh2 mutant mouse. Deletion of Impdh2 in the early neural crest using the Wnt1-Cre transgene produced defects in multiple neural crest derivatives including highly penetrant intestinal aganglionosis, agenesis of the craniofacial skeleton, and cardiac outflow tract and great vessel malformations. Analysis using a Rosa26 reporter mouse suggested that some or all of the remaining ENS in Impdh2 conditional-knockout animals was derived from cells that escaped Wnt1-Cre mediated DNA recombination. These data suggest that IMPDH2 mediated guanine nucleotide synthesis is essential for normal development of the ENS and other neural crest derivatives.

Loss of Tbx3 in murine neural crest reduces enteric glia and causes cleft palate, but does not influence heart development or bowel transit

“…For this study, we investigated the role of Tbx3, a transcription factor that is highly expressed in developing ENS relative to other cells of the bowel. We demonstrated that Wnt1-Cre efficiently depleted TBX3 from ENCDC, as expected since prior studies show Wnt1-Cre induces almost complete recombination in the ENS lineage (Lake et al, 2016). We found that Tbx3 is not required within ENCDCs for prenatal bowel colonization by ENS precursors, that Tbx3 fl/fl; Wnt1-Cre mice had a normal density of enteric neurons at P0, and that transit of FITC-dextran though the upper gastrointestinal tract occurred at a normal rate despite a reduced number of enteric glia.…”

“…For this study, Wnt1-Cre; Rosa26EYFP reporter mice were employed for fluorescence-activated cell sorting to separate EYFP expressing ENCDC from other cells of the bowel wall. This is a commonly used mouse line that expresses EYFP in essentially all ENCDC (>99.9%), but not in other cells of the bowel wall (Lake et al, 2016). As expected, we identified many differentially expressed genes encoding transcription factors, as well as other proteins (Figure 1).…”

“…To further understand the role of Tbx3 in ENS development, we generated conditional Tbx3 fl/fl; Wnt1-Cre mutant mice. In this mouse line, Wnt1-Cre induces DNA recombination to inactivate Tbx3 in essentially all enteric nervous system precursors and their mature progeny (collectively called enteric neural crest-derived cells (ENCDC)) (Frank et al, 2013; Lake et al, 2016). Wnt1-Cre also inactivates Tbx3 in other neural crest-derived tissue including great vessels of the heart and craniofacial bones (Jiang et al, 2002; Lee et al, 2004).…”

Animal Models of Hirschsprung's Disease: State of the Art in Translating Experimental Research to the Bedside

“…21 Furthermore, Lake et al reported that inhibiting inosine 5′ monophosphate dehydrogenase 2 (Impdh2) produced defects in multiple neural crest derivatives, including intestinal aganglionosis, agenesis of the craniofacial skeleton, and cardiac outflow tract with malformations of major vessels. 19,22…”

Mouse models of Hirschsprung disease and other developmental disorders of the enteric nervous system: Old and new players

“…MPA blocks the rate-limiting step of de novo guanine nucleotide synthesis by inhibiting inosine 5’ monophosphate dehydrogenase (IMPDH), a ubiquitous metabolic enzyme whose expression is relatively enriched in ENCCs. To further explore the role for this basic metabolic pathway, Lake et al recently deleted Impdh2 using a conditional allele crossed with the Wnt1-Cre transgene, and observed defects in multiple neural crest derivatives, including highly penetrant intestinal aganglionosis, agenesis of the craniofacial skeleton, and cardiac outflow tract with great vessel malformations (Lake et al, 2016). ENS defects in mutants lacking Impdh2 within the neural crest are clearly visible from E13.5 and demonstrate a critical role for de novo guanine nucleotide biosynthesis in ENS development.…”