Retinaldehyde dehydrogenase 2 is down-regulated during duodenal atresia formation in Fgfr2IIIb-/- mice
Peter F Nichol1, John D Tyrrell, Yukio Saijoh
1Department of Surgery, Section of Pediatric Surgery, University of Wisconsin SMPH, Madison, Wisconsin 53792, USA. nichol@surgery.wisc.edu
Background:
Homozygous null mutation of fibroblast growth factor receptor 2 (Fgfr2IIIb) or its ligand fibroblast growth factor 10 (Fgf10) results in duodenal atresia in mice. Mutations of either of these genes in humans cause Matthew-Wood syndrome and associated duodenal stenosis. Recently, mutations in the retinol-binding protein receptor gene STRA6 were reported to be implicated in this syndrome as well. This suggests that the retinoic acid (RA) signaling pathway interacts with the Fgf10-Fgfr2IIIb signaling pathway during duodenal development. Accordingly, we hypothesized that Fgfr2IIIb-/- mouse embryos would exhibit disruptions in expression of Raldh2, the gene for the enzyme that regulates the final step in the conversion of vitamin A to the active form RA, during duodenal atresia formation.
Materials And Methods:
Fgfr2III -/- mice were generated from heterozygous breedings. Embryos were harvested between embryonic day (E) 11.0 to E 13.5 and genotyped by polymerase chain reaction (PCR). Duodenums were dissected out, fixed and photographed. Whole mount and section in situs were performed for Raldh2.
Results:
Fgfr2IIIb-/- embryos demonstrate subtle changes in the duodenal morphology by E11.5 with complete involution of the atretic precursor by E 13.5. Raldh2 appears to be down-regulated as early as E 11.5 in the atretic precursor a full 2 days before this segment disappears.
Conclusions:
In Fgfr2IIIb-/- mouse embryos, a reduction of Raldh2 expression is observed within the region that is forming the atresia. This is the first demonstration of such an event in this model. As in humans, these results implicate disruptions between Fgfr2IIIb receptor function and RA signaling in the formation of this defect and indicate that Fgfr2IIIb-/- mouse embryos are a valid model for the study of the atretic spectrum of defects in human duodenal development.
Insights
Fibroblast growth factor receptor 2 (Fgfr2IIIb) mutations disrupt duodenal development by down-regulating Raldh2 expression. This study validates Fgfr2IIIb-/- mice as a model for studying human duodenal atresia and stenosis.
Area of Science:
- Developmental biology
- Genetics
- Molecular signaling
Background:
- Homozygous null mutations in fibroblast growth factor receptor 2 (Fgfr2IIIb) or fibroblast growth factor 10 (Fgf10) cause duodenal atresia in mice.
- Human mutations in Fgfr2IIIb or Fgf10 lead to Matthew-Wood syndrome and duodenal stenosis.
- Recent findings implicate STRA6 gene mutations in Matthew-Wood syndrome, suggesting retinoic acid (RA) pathway involvement.
Purpose of the Study:
- To investigate the interaction between Fgf10-Fgfr2IIIb and RA signaling pathways in duodenal development.
- To test the hypothesis that Fgfr2IIIb-/- mouse embryos exhibit disrupted Raldh2 expression during duodenal atresia formation.
Main Methods:
- Generation of Fgfr2IIIb-/- mice from heterozygous breedings.
- Harvesting and genotyping of embryos between embryonic day (E) 11.0 to E 13.5.
- Dissection, fixation, and photography of duodenums.
- Whole mount and section in situ hybridization for Raldh2 expression analysis.
Main Results:
- Fgfr2IIIb-/- embryos showed subtle duodenal morphological changes by E11.5, with complete involution of the atretic precursor by E13.5.
- Raldh2 expression was down-regulated as early as E11.5 in the atretic precursor, two days before its disappearance.
- A reduction in Raldh2 expression was observed in the developing atretic region of Fgfr2IIIb-/- mouse embryos.
Conclusions:
- Disruptions in Fgfr2IIIb receptor function and RA signaling are implicated in human duodenal atresia and stenosis.
- Fgfr2IIIb-/- mouse embryos demonstrate reduced Raldh2 expression, supporting the link between these pathways.
- Fgfr2IIIb-/- mouse embryos serve as a valid model for studying human duodenal atretic defects.
