Probes for TUBB3

Gain-of-function mutations in Scn9a, which encodes the peripheral sensory neuron-enriched voltage-gated sodium channel Nav1.7, cause paroxysmal extreme pain disorder (PEPD), inherited erythromelalgia (IEM), and small fiber neuropathy (SFN). Conversely, loss-of-function mutations in the gene are linked to congenital insensitivity to pain (CIP). These mutations are evidence for a link between altered sodium conductance and neuronal excitability leading to somatosensory aberrations, pain, or its loss. Our previous work in young adult mice with the Nav1.7 gain-of-function mutation, I228M, showed the expected DRG neuron hyperexcitability, but unexpectedly the mice had normal mechanical and thermal behavioral sensitivity. We now show that with aging both male and female mice with this mutation unexpectedly develop a profound insensitivity to noxious heat and cold, as well skin lesions that span the body. Electrophysiology demonstrates that, in contrast to young mice, aged I228M mouse DRGs have a profound loss of sodium conductance and changes in activation and slow inactivation dynamics, representing a loss-of-function. Through RNA sequencing we explored how these age-related changes may produce the phenotypic changes and found a striking and specific decrease in C-low threshold mechanoreceptor- (cLTMR) associated gene expression, suggesting a potential contribution of this DRG neuron subtype to Nav1.7 dysfunction phenotypes. A GOF mutation in a voltage-gated channel can therefore produce over a prolonged time, highly complex and unexpected alterations in the nervous system beyond excitability changes.

Sensory neurons of the dorsal root ganglion (DRG) are critical for maintaining tissue homeostasis by sensing and initiating responses to stimuli. While most preclinical studies of DRGs are conducted in rodents, much less is known about the mechanisms of sensory perception in primates. We generated a transcriptome atlas of mouse, guinea pig, cynomolgus monkey, and human DRGs by implementing a common laboratory workflow and multiple data-integration approaches to generate high-resolution cross-species mappings of sensory neuron subtypes. Using our atlas, we identified conserved core modules highlighting subtype-specific biological processes related to inflammatory response. We also identified divergent expression of key genes involved in DRG function, suggesting species-specific adaptations specifically in nociceptors that likely point to divergent function of nociceptors. Among these, we validated that TAFA4, a member of the druggable genome, was expressed in distinct populations of DRG neurons across species, highlighting species-specific programs that are critical for therapeutic development.