Fig. 6

Retinoic acid signaling regulates induction of RUNX3 expression in PSNs. a Section of the brachial region of an HHst23 chicken embryo showing expression of the RA-synthesizing enzyme RALDH2 at the time of physiological induction of RUNX3. Scale bar: 50 μm. b RUNX3 expression is induced in the presence of RA (500 ng/ml) in a subset of ISL1⁺ DRG neurons from HHst23 embryos within 12 h of treatment. Scale bar: 50 μm. c Concentration-dependent response of RA treatment on RUNX3 levels (n = 3). d Immunohistochemistry for ISL1, TRKC and RUNX3 on brachial DRG sections from E11.5 WT and Raldh2^−/− mice. Scale bar: 20 μm. e Quantification of d, showing no difference in the number of ISL1 or TRKC positive neurons in Raldh2^−/− mice (n = 3, unpaired Student’s t-test). f Quantification of RUNX3 expression in TRKC⁺ neurons of d shows an overall decrease in intensity (^*P < 0.05, unpaired Student’s t-test) and a significant F test (F = 0.0009) indicating a larger spreading of the variance between Raldh2^+/+ and Raldh2^−/− mice (n = 3). g Quantification of TRKC expression in d shows significant decrease in its level of intensity per cell in the Raldh2^−/− compared to Raldh2^+/+ mice (^***P < 0.001, unpaired Student’s t-test). h Quantification of TRKC⁺/RUNX3⁺ DRG neurons on sections from E12.5 Raldh2^+/+ and Raldh2^−/− mice shows a twofold decrease in the number of PSNs in the mutants (^**P < 0.01, unpaired Student’s t-test, n = 4). i Number of PSNs is also largely decreased at E13.5 in the Raldh1/2/3^cKO (R^cKO) mutant mice compared to the control mice Raldh1/2/3 (Cre^−/−) (n = 3,^*P < 0.05, unpaired Student’s t-test). j Proposed model for the selection of the TRKC DRG neurons during development, in which neurons, soon after being generated, feature different functional molecular signatures that are predictive of their survival or death during the cell death period (E12–E12.5). Source data are available as a Source Data file