Rescue of proliferation defects in dorsal root ganglia precursors of βcat-Sig embryos. (A, E, I) Illustration of a transverse section at E9, E10.5, and E12.5, respectively, displaying cells contributing to the DRG in red. Green box represents caption area for subfigures B-D, F-H and J-L, respectively. (B-D, F-H, J-L) Immunofluorescent staining for Sox10 and detection of EdU from a one-hour pulse. Dashed lines frame cells of the R26R reporter fate mapped in vivo, which were detected by an immunofluorescent co-staining for β-gal on the corresponding sections. (B-D, B’-D’) No difference in the amount of Sox10- and EdU- double positive cells is apparent between the three types of embryos at E9. Arrows: Sox10 and EdU co-expressing cells. (F-H, F’-H’) At E10.5, both mutant animals display reduced incorporation of EdU in Sox10-positive DRG progenitors. (J-L, J’-L’) However, Sox10-positive cells of βcat-Sig R26R embryos recover the ability to incorporate EdU at E12.5, while Sox10-positive cells of βcat-Null R26R embryos of the same age do not. Arrows: Sox10 and EdU co-expressing cells, Arrowheads: Sox10-positive EdU-negative cells. (M) Quantification of the average numbers of R26R-positive cells contributing to the DRG at E9, E10.5 and E12.5 reveals no significant differences between mutant and control animals at E9 and E10.5. However, at E12.5 there is a statistically significant decrease of cells populating the DRG in both mutant animals. The decrease is significantly stronger in βcat-Null R26R embryos than in βcat-Sig R26R embryos. (N) Percentages of EdU-positive cells in the Sox10-positive population display a significant reduction of EdU incorporation in βcat-Null R26R animals at E10.5 and E12.5. Whereas βcat-Sig R26R animals exhibit similar statistically significant reduction as βcat-Null R26R animals at E10.5, they recover the ability to incorporate EdU by E12.5. NT, neural tube; * indicates P <0.05; Scale bars: 25 μm. DRG, dorsal root ganglia; E, embryonic day; EdU, 5-ethynyl-2′-deoxyuridine.