Figure 4. Ret and Gfra2 null mice display different central projection and cell survival deficits at E18.5.

(A–H) SC sections and whole mount L4/L5 DRGs of Tdt labeled RA mechanoreceptor from E18.5 Ret^CreERT/+;Rosa^Tdt control (A–B), Ret^{CreERT/CreERT};Rosa^Tdt mutant (C–D), Gfra2^GFP/+;Ret^CreERT/+;Rosa^Tdt control (E–F), and Gfra2^GFP/GFP;Ret^CreERT/+;Rosa^Tdt mutant (G–H) embryos. (I) Quantification of Tdt⁺ pixels in dSC, which is displayed as a percentage normalized to dSC Tdt⁺ pixels of the within litter controls. (J) Quantification of the number of Tdt⁺ DRG neurons per whole-mount L4/L5 DRG, which is displayed as a percentage normalized to Tdt⁺ neurons of the within litter controls. Ret mutants have significant decreases in RA mechanosensory axons innervating the dSC and in the number of Tdt⁺ RA mechanoreceptors, suggesting that Ret mutants have deficits in both the growth of third order central projections and the survival of RA mechanoreceptors at E18.5. In contrast, Gfra2 nulls have only minor deficits in RA mechanosensory central projection growth and the survival or RA mechanoreceptors, suggesting that an additional GFRa2 independent but RET-dependent mechanism functions in these processes. Scale bar = 50 μm. Error bars represent SEM. * = p < 0.05, *** = p < 0.001. Source data are provided in Figure 4—source data 1.

DOI: http://dx.doi.org/10.7554/eLife.06828.013

Figure 4—figure supplement 1. Gfra2 null RA mechanoreceptors retain phospho-S6 expression.

(A–B) Anti-GFP (green) and anti-phospho-S6 (red) staining of P0 Gfra2^GFP/+ control (A) and Gfra2^GFP/GFP null (B) DRG sections. (C) Quantification of percentage of GFP⁺ neurons which express phospho-S6 shows no significant change in proportion of phospho-S6⁺ RA mechanoreceptors (92.53 ± 1.55% of Gfra2^GFP/+ GFP⁺ DRG neurons express phospho-S6, 93.66 ± 0.14% of Gfra2^GFPGFP+ GFP⁺ DRG neurons express phospho-S6, p = 0.51). Therefore, active RTK signaling seems to still occur in Gfra2 null RA mechanoreceptors.

DOI: http://dx.doi.org/10.7554/eLife.06828.015