Figure 6.
Proposed model of the developmental relationship between the different sensory neuron subtypes. At E11.5, TRP-negative cells (gray) acquire TRPV1 (red) until the peak at E14.5, after which some cells will downregulate TRPV1. These cells give rise to the TRPV1−, IB4+ cells and some of the TRPV1−, IB4− cells. Before birth, at E18.5, the cells expressing TRPM8 (green and brown) are specified from within the TRPV1-positive population. Some cells subsequently downregulate TRPV1, giving rise to two populations of TRPM8-positive neurons (with or without TRPV1; brown and green, respectively). Within the IB4-negative population, the TRPA1-positive cells derive from TRPV1-positive neurons perinatally, whereas within the IB4-positive population, the TRPA1-expressing cells arise >2 weeks later. Some of the TRPA1- and TRPV1-coexpressing cells (orange) will also downregulate TRPV1, giving rise to TRPA1-only neurons (yellow). A1, TRPA1; M8, TRPM8; neg, negative.