Three-dimensional reconstruction of intestinal tracts from control and Fgfr2IIIb mutant embryos aged E9.5-E12.5. Note that for E9.5-E10.5 the epithelial cells from the entirety of the intestinal tract are present, whereas only the cecum to distal colon are visualized in the E11.5-E12.5 reconstructions. Pan-epithelial apoptosis is present in both the control and null embryos at E9.5 (A and A’). At E10.5, there is a decrease in apoptosis globally, but a greater decrease in the distal colon of the null embryo (B and B’). By E11.5, apoptosis is largely absent outside of the developing cecal region (C and C’). At E12.5, little to no apoptosis is seen (D and D’). Note the shortened intestinal tract in D’, indicative of the distal colonic atresia and loss of the distal colon. Abbreviations: Prox= proximal, Dist= distal, SI= small intestine, Co = colon