Fig. 1

Differential expression of TRKC in PSNs prior to the cell death period. a Scheme of our working hypothesis. b, c Temporal fate mapping of TRKC PSNs by 4-OHT induction. TrkC^CreER mice allow temporary activation of CreER in the TRKC⁺ cells 2 h after 4-OHT injection^21,22. Immunostaining for PV, RFP and RUNX3 on E17.5 DRG sections (c) and graph showing distribution of PV⁺/RUNX3⁺ PSNs among the TOM⁺ cells (n = 4). Scale bar: 20 μm. d Quantification of PSNs at C5 and C7. ***P < 0.001, one-way analysis of variance (ANOVA) with Sidak’s multiple comparisons test (n = 2–3). The window of PSNs cell death is shown. e TRKC expression in E11.5 ISL1⁺ (and RUNX3⁺, whose staining is not shown for more visibility) DRG neurons. Scale bar: 50 μm. f TRKC levels in PSNs of e illustrated by color coding; dark blue indicates the lower and red the higher TRKC levels. From here, all observations are done at brachial levels (C5–8). g Distribution of TRKC levels in PSNs from e. h Distribution of TRKC levels in PSNs in E11.5 DRG neurons (from g). The data exhibit a Poisson-like distribution (one representative animal), with the mean used to define the two different categories of TRKC intensity (TRKC^High and TRKC^Low). i Projection of seven images of RUNX3⁺/TRKC⁺ PSNs from one brachial DRG; dots indicate TRKC-labeled neurons and color codes reveal TRKC intensity as shown in h. j Projection image of smFISH for pan Ntrk3 and Ntrk3 full length (FL) transcripts in E11.5 DRG, visualized at high magnification in (1) and (2) (images show full projection); right panel shows color coding of Ntrk3 FL levels in red; the brighter, the higher levels. k Distribution of the number of Ntrk3 FL molecules in E11.5 DRG neurons by smFISH, normalized to pan Ntrk3 (Ntrk3 FL represent 68% of all Ntrk3 transcripts). l TrkC^CreER;R26^tdTOM mice were injected at E9.75 with 4-OHT and analyzed at E11.5 (n = 3). m, n Frequency distribution (m) and pie chart (n) of TOM⁺/TRKC⁺ neurons from l according to their level of TRKC intensity. Source data are available as a Source Data file