Figure 3. Central projection growth deficit of Gfra2 null RA mechanoreceptors at E15.5.

(A–I) E15.5 Gfra2^GFP/+;Ret^CreERT/+;Rosa^Tdt DRG sections stained with anti-RET (A–C), anti-NTRK1 (D–F), and anti-GFP (G–I). (J) Quantification of percentage of Tdt⁺ DRG neurons which co-express RET (96.16 ± 0.28%), NTRK1 (6.56 ± 0.18%), and GFP driven from the Gfra2 locus (86.48 ± 0.55%). The expression profile of Tdt⁺ neurons confirms that this genetic labeling strategy specifically labels RA mechanoreceptors. (K–L) Visualization of Tdt⁺ RA mechanosensory central projections in dSC of E15.5 Gfra2^GFP/+; Ret^CreERT/+; Rosa^Tdt control (K) and Gfra2^GFP/GFP; Ret^CreERT/+; Rosa^Tdt mutant (L) SC sections. (M) Quantification of Tdt⁺ pixels in dSC, which is displayed as a percentage normalized to dSC Tdt⁺ pixels of the within litter controls. Gfra2 mutant mice have 55.13 ± 2.82% of control staining (p < 0.001). Note that although Gfra2 null RA mechanoreceptors still have a central projection deficit at E15.5, the reduction at this stage is less severe than the deficit observed at E13.5. (N) Quantification of number of Tdt⁺ neurons per DRG section, which is displayed as a percentage normalized to Tdt⁺ neurons of the within litter controls. Gfra2 mutant mice have 79.52 ± 8.39% of control cell number (p = 0.06), which suggests that the survival of RA mechanoreceptors is not dependent on cis signaling at this stage. Scale bars = 100 μm (A–I), 50 μm (K–L). Error bars represent SEM. n.s. = p > 0.05, *** = p < 0.001. Source data are provided in Figure 3—source data 1.

DOI: http://dx.doi.org/10.7554/eLife.06828.010

Figure 3—figure supplement 1. Generation of tandem Ret^CreERT;Rosa^Tdt allele.

The Ret and Rosa loci are located ∼5 megabases apart on mouse chromosome 6. Ret^CreERT/+ mice were crossed to Rosa^Tdt/Tdt mice to generate Ret^CreERT/+;Rosa^Tdt/+ mice, which were crossed back to Rosa^Tdt/Tdt mice. Occasionally, an interchromosomal recombination event occurred between the Ret and Rosa loci, which caused Ret^CreERT and Rosa^Tdt to be located on the same chromosome. Recombinants were identified by genotyping for the Ret^CreERT allele and the homozygous presence of the Rosa^Tdt allele. The chromosome containing both Ret^CreERT and Rosa^Tdt alleles is called the tandem Ret^CreERT;Rosa^Tdt allele and maintained by mating with Rosa^Tdt/Tdt mice.

DOI: http://dx.doi.org/10.7554/eLife.06828.012