Transcriptional Profiling of Cutaneous MRGPRD Free Nerve Endings and C-LTMRs

Cutaneous C-unmyelinated MRGPRD⁺ free nerve endings and C-LTMRs innervating hair follicles convey two opposite aspects of touch sensation: a sensation of pain and a sensation of pleasant touch. The molecular mechanisms underlying these diametrically opposite functions are unknown. Here, we used a mouse model that genetically marks C-LTMRs and MRGPRD⁺ neurons in combination with fluorescent cell surface labeling, flow cytometry, and RNA deep-sequencing technology (RNA-seq). Cluster analysis of RNA-seq profiles of the purified neuronal subsets revealed 486 and 549 genes differentially expressed in MRGPRD-expressing neurons and C-LTMRs, respectively. We validated 48 MRGPD- and 68 C-LTMRs-enriched genes using a triple-staining approach, and the Ca_v3.3 channel, found to be exclusively expressed in C-LTMRs, was validated using electrophysiology. Our study greatly expands the molecular characterization of C-LTMRs and suggests that this particular population of neurons shares some molecular features with Aβ and Aδ low-threshold mechanoreceptors.