Fig 2: TH expression in the GG. A, Fluorescence in situ hybridization labeling of GG sections from adult C57Bl/6 mice using probes to Phox2b (green) and Th (blue) revealed neurons that express high levels of Th (yellow arrow) and low levels of Th (white arrow). B, Immunofluorescence labeling of adult GG from Th-CreER; RosaRFP mice using antibodies to TUJ1 (green), PHOX2B (blue), and RFP (magenta) identifies a population of PHOX2B+ neurons that also express RFP (Th). C, Immunofluorescence labeling of Th-WT; RosaRFP mice, as in B, confirms the specificity of the RFP immunoreactions. Immunofluorescence labeling of nodose/petrosal/jugular ganglion complexes from Th-CreER; RosaRFP mice using the same antibodies in B demonstrated the presence of Th+/PHOX2B+ oral sensory neurons in petrosal ganglia as well, shown in Extended Data Figure 1-1. D, Serial sections of GG evaluated with both methods were counted and quantified to determine what percentage of Phox2b+ neurons coexpressed Th. Only high Th-expressing neurons are graphed in D for the in situ hybridization. The p value is p = 0.0027. E, Serial sections of GG were quantified to determine the number of Th-expressing neurons that did not express Phox2b. Error bars represent mean ± SEM, and n = 3–4 mice were analyzed by each method. The p value is p = 0.2797. Scale bar in A is 100 µm, and the scale bar in B is 100 µm and applies to all panels in C. ** denotes p < 0.01, and ns is not statistically significant.

Fig 3: Fibers from Th+ oral sensory neurons enter the rostral portion of the NTS. A, Th-CreER; RosaRFP mice were administered tamoxifen and allowed to recover for three weeks before the brainstem was isolated. Coronal serial sections through the NTS were immunolabeled with antibodies to TUJ1 (green) and RFP (magenta). The white arrows indicate the solitary tract that is lateral to the NTS (indicated with yellow arrows). Successive sections are displayed progressing from top row to bottom row so that the progression of the solitary tract to the NTS can be appreciated. Scale bar: 100 µm. B, Th-CreER; Phox2b-FLPO; RC::FLTG mice were administered tamoxifen and allowed to recover for three weeks. Coronal serial sections were immunolabeled with antibodies to TUJ1 (blue) and eGFP (green). The white arrows indicate the solitary tract and yellow arrows denote the NTS. The bottom row is a higher power image of the row above it. The scale bars are 100 µm. The scale bar in the first row in A applies to all panels in A, and the scale bar in B applies to all panels in B. Four independent mice of each genotype were analyzed in A and B.

Fig 4: Geniculate ganglion neurons are not lost in either Phox2b-Cre; p75fx/fx or P0-Cre; p75fx/fx mice. (A) Geniculate ganglia from P0-Cre; p75fx/fx mice, P0-WT; p75fx/fx mice, Phox2b-Cre; p75fx/fx mice and Phox2b-WT; p75fx/fx mice were isolated and immunolabeled for Tuj1. (B) The total number of geniculate neurons was quantified from these images by counting Tuj1 + neurons when p75 was deleted specifically in Phox2b + oral sensory neurons (Phox2b-Cre; p75fx/fx) or in neural crest-derived cells (P0-Cre; p75fx/fx), and their wild type littermates, at 6–8 weeks of age. These data indicate that the total number of geniculate neurons does not change in either Phox2b-Cre; p75fx/fx or P0-Cre; p75fx/fx mice. (C) The somal diameters of geniculate neurons from Phox2b-Cre; p75fx/fx, Phox2b-WT; p75fx/fx, P0-Cre; p75fx/fx and P0-WT; p75fx/fx mice were measured. There were no differences in the average somal diameters among any of these groups. The data in this figure are represented as the mean ± SEM; n = 3–5 for each group.

Fig 5: Neural deletion of p75 results in a moderate loss of fungiform taste buds. The tongues from 9–12-month-old Phox2b-Cre; p75fx/fx and Phox2b-WT; p75fx/fx mice were serially sectioned, H&E stained and the number of taste buds within fungiform papillae counted. While the majority of fungiform papillae contained taste buds with normal morphology (A), some had abnormal, shrunken taste buds or none at all (B). (C) Quantification of the number of taste buds revealed a reduction in Phox2b-Cre; p75fx/fx mice compared to Phox2b-WT; p75fx/fx mice. (D) Numbers of fungiform papillae were unchanged between genotypes. (E) The number of taste buds in 2–3-month-old Phox2b-Cre; p75fx/fx mice was reduced as compared to Phox2b-WT; p75fx/fx mice. Sample sizes are 3–6 mice per group and data are graphed as the mean ± SEM. * is p < 0.05. Scale bar in (B) is 25 µm.