Transcriptional profiling at whole population and single cell levels reveals somatosensory neuron molecular diversity

Abstract

The somatosensory nervous system is critical for the organism's ability to respond to mechanical, thermal, and nociceptive stimuli. Somatosensory neurons are functionally and anatomically diverse but their molecular profiles are not well-defined. Here, we used transcriptional profiling to analyze the detailed molecular signatures of dorsal root ganglion (DRG) sensory neurons. We used two mouse reporter lines and surface IB4 labeling to purify three major non-overlapping classes of neurons: + cells, encompassing the majority of nociceptive, pruriceptive, and proprioceptive neurons. These neurons displayed distinct expression patterns of ion channels, transcription factors, and GPCRs. Highly parallel qRT-PCR analysis of 334 single neurons selected by membership of the three populations demonstrated further diversity, with unbiased clustering analysis identifying six distinct subgroups. These data significantly increase our knowledge of the molecular identities of known DRG populations and uncover potentially novel subsets, revealing the complexity and diversity of those neurons underlying somatosensation.

Somatosensory neuron types identified by high-coverage single-cell RNA-sequencing and functional heterogeneity

“…We suggest a new catalog of DRG neuron types, including 6 types and 10 subtypes of small neurons, and 4 types and 4 subtypes of large neurons with single or combined markers. In addition to the well-known neuron types (C1, C3, C4, C5, C9 and C10), our present data indicate that Nppb-marked C2 is an independent neuron type, consistent with other recent proposals [25,34]. Neuron types C6, C7 and C8, and all corresponding subtypes have not been previously reported.…”

“…The transcriptional profiles of TRPV1 lineage and Na v 1.8 channel-expressing DRG neurons have been examined by RNA-seq [23,24]. By single-cell PCR, Chiu et al identified six subgroups of DRG neurons [25]. Single-cell RNA-seq enables a better understanding of a cell's transcriptome [26][27][28][29][30][31][32][33].…”

Evolutionary Specialization of Tactile Perception in Vertebrates

“…For example, in mouse DRG, rapidly adapting LTMRs account for ϳ6% of all DRG neurons (45), yet this type of afferent innervates several classes of mechanoreceptive end-organs: Pacinian corpuscles, Meissner corpuscles, and lanceolate endings surrounding guard and awl/auchene hairs. Recent studies utilizing microarray-based and single-cell PCR-based transcriptomic approaches further highlight the functional heterogeneity of rodent DRG neurons, which remain the main experimental model in sensory physiology (13,76). These considerations catalyze the need to turn investigators' attention to tactile specialists who possess an increased proportion of LTMRs in their sensory ganglia.…”

TRPV1 antagonists in the treatment of osteoarthritis pain

“…In DRG neurones TRPV1 is coexpressed with proteinase-activated receptor 2 [23] and cannabinoid CB1 receptors [24] that have pro-and anti-nociceptive roles in joints respectively [25,26]. A recent transcriptional profiling study of DRG neurones [27] demonstrated that TRPV1 is expressed in distinct subsets of neurones one of which expresses high levels of TrKA and Nav1.8 as well as significant levels of aquaporin 1 and Kv8.1 thought to function as thermosensitive C-fibers. At the level of the dorsal horn of the spinal cord, TRPV1 is localized in both presynaptic afferent neurones where it is coexpressed with the neuropeptide CGRP, and in postsynaptic neurones as well as glia in lamina I and II [10, 28,29].…”