Nav1.7 gain-of-function mutation I228M triggers age-dependent nociceptive insensitivity and C-LTMR dysregulation

Experimental neurology

2023 Mar 30

Wimalasena, NK;Taub, DG;Shim, J;Hakim, S;Kawaguchi, R;Chen, L;El-Rifai, M;Geschwind, D;Dib-Hajj, SD;Waxman, SG;Woolf, CJ;
PMID: 37003485 | DOI: 10.1016/j.expneurol.2023.114393

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.

Diversity amongst trigeminal neurons revealed by high throughput single cell sequencing

PLoS ONE

2017 Sep 28

Nguyen MQ, Wu Y, Bonilla LS, von Buchholtz LJ, Ryba NJP.
PMID: 28957441 | DOI: 10.1371/journal.pone.0185543

The trigeminal ganglion contains somatosensory neurons that detect a range of thermal, mechanical and chemical cues and innervate unique sensory compartments in the head and neck including the eyes, nose, mouth, meninges and vibrissae. We used single-cell sequencing and in situ hybridization to examine the cellular diversity of the trigeminal ganglion in mice, defining thirteen clusters of neurons. We show that clusters are well conserved in dorsal root ganglia suggesting they represent distinct functional classes of somatosensory neurons and not specialization associated with their sensory targets. Notably, functionally important genes (e.g. the mechanosensory channel Piezo2 and the capsaicin gated ion channel Trpv1) segregate into multiple clusters and often are expressed in subsets of cells within a cluster. Therefore, the 13 genetically-defined classes are likely to be physiologically heterogeneous rather than highly parallel (i.e., redundant) lines of sensory input. Our analysis harnesses the power of single-cell sequencing to provide a unique platform for in silico expression profiling that complements other approaches linking gene-expression with function and exposes unexpected diversity in the somatosensory system.

Transcriptional Programming of Human Mechanosensory Neuron Subtypes from Pluripotent Stem Cells.

Cell Rep

2020 Jan 21

Nickolls AR, Lee MM, Espinoza DF, Szczot M, Lam RM, Wang Q, Beers J, Zou J, Nguyen MQ, Solinski HJ, AlJanahi AA, Johnson KR, Ward ME, Chesler AT, B�nnemann CG
PMID: 31968264 | DOI: 10.1016/j.celrep.2019.12.062

Efficient and homogeneous in vitro generation of peripheral sensory neurons may provide a framework for novel drug screening platforms and disease models of touch and pain. We discover that, by overexpressing NGN2 and BRN3A, human pluripotent stem cells can be transcriptionally programmed to differentiate into a surprisingly uniform culture of cold- and mechano-sensing neurons. Although such a neuronal subtype is not found in mice, we identify molecular evidence for its existence in human sensory ganglia. Combining NGN2 and BRN3A programming with neural crest patterning, we produce two additional populations of sensory neurons, including a specialized touch receptor neuron subtype. Finally, we apply this system to model a rare inherited sensory disorder of touch and proprioception caused by inactivating mutations in PIEZO2. Together, these findings establish an approach to specify distinct sensory neuron subtypes in vitro, underscoring the utility of stem cell technology to capture human-specific features of physiology and disease.

Keratinocytes produce IL-17c to protect peripheral nervous systems during human HSV-2 reactivation

J Exp Med.

2017 Jun 29

Peng T, Chanthaphavong RS, Sun S, Trigilio JA, Phasouk K, Jin L, Layton ED, Li AZ, Correnti CE, De van der Schueren W, Vazquez J, O’Day DR, Glass IA, Knipe DM, Wald A, Corey L, Zhu J.
PMID: 28663436 | DOI: 10.1084/jem.20160581

Abstract

Despite frequent herpes simplex virus (HSV) reactivation, peripheral nerve destruction and sensory anesthesia are rare. We discovered that skin biopsies obtained during asymptomatic human HSV-2 reactivation exhibit a higher density of nerve fibers relative to biopsies during virological and clinical quiescence. We evaluated the effects of HSV infection on keratinocytes, the initial target of HSV replication, to better understand this observation. Keratinocytes produced IL-17c during HSV-2 reactivation, and IL-17RE, an IL-17c-specific receptor, was expressed on nerve fibers in human skin and sensory neurons in dorsal root ganglia. In ex vivo experiments, exogenous human IL-17cprovided directional guidance and promoted neurite growth and branching in microfluidic devices. Exogenous murine IL-17c pretreatment reduced apoptosis in HSV-2-infected primary neurons. These results suggest that IL-17c is a neurotrophic cytokine that protects peripheralnerve systems during HSV reactivation. This mechanism could explain the lack of nerve damage from recurrent HSV infection and may provide insight to understanding and treating sensory peripheral neuropathies.

Dual leucine zipper kinase is required for mechanical allodynia and microgliosis after nerve injury.

Elife.

2018 Jul 03

Wlaschin JJ, Gluski JM, Nguyen E, Silberberg H, Thompson JH, Chesler AT, Le Pichon CE.
PMID: 29968565 | DOI: 10.7554/eLife.33910

Neuropathic pain resulting from nerve injury can become persistent and difficult to treat but the molecular signaling responsible for its development remains poorly described. Here, we identify the neuronal stress sensor dual leucine zipper kinase (DLK; Map3k12) as a key molecule controlling the maladaptive pathways that lead to pain following injury. Genetic or pharmacological inhibition of DLK reduces mechanical hypersensitivity in a mouse model of neuropathic pain. Furthermore, DLK inhibition also prevents the spinal cord microgliosis that results from nerve injury and arises distant from the injury site. These striking phenotypes result from the control by DLK of a transcriptional program in somatosensory neurons regulating the expression of numerous genes implicated in pain pathogenesis, including the immune gene Csf1. Thus, activation of DLK is an early event, or even the master regulator, controlling a wide variety of pathways downstream of nerve injury that ultimately lead to chronic pain.

Nppb Neurons Are Sensors of Mast Cell-Induced Itch

Cell Rep

2019 Mar 26

Solinski HJ, Kriegbaum MC, Tseng PY, Earnest TW, Gu X, Barik A, Chesler AT and Hoon MA
PMID: 30917312 | DOI: 10.1016/j.celrep.2019.02.089

Itch is an unpleasant skin sensation that can be triggered by exposure to many chemicals, including those released by mast cells. The natriuretic polypeptide b (Nppb)-expressing class of sensory neurons, when activated, elicits scratching responses in mice, but it is unclear which itch-inducing agents stimulate these cells and the receptors involved. Here, we identify receptors expressed by Nppb neurons and demonstrate the functional importance of these receptors as sensors of endogenous pruritogens released by mast cells. Our search for receptors in Nppb neurons reveals that they express leukotriene, serotonin, and sphingosine-1-phosphate receptors. Targeted cell ablation, calcium imaging of primary sensory neurons, and conditional receptor knockout studies demonstrate that these receptors induce itch by the direct stimulation of Nppb neurons and neurotransmission through the canonical gastrin-releasing peptide (GRP)-dependent spinal cord itch pathway. Together, our results define a molecular and cellular pathway for mast cell-induced itch.

	Description
sense Example: Hs-LAG3-sense	Standard probes for RNA detection are in antisense. Sense probe is reverse complent to the corresponding antisense probe.
Intron# Example: Mm-Htt-intron2	Probe targets the indicated intron in the target gene, commonly used for pre-mRNA detection
Pool/Pan Example: Hs-CD3-pool (Hs-CD3D, Hs-CD3E, Hs-CD3G)	A mixture of multiple probe sets targeting multiple genes or transcripts
No-XSp Example: Hs-PDGFB-No-XMm	Does not cross detect with the species (Sp)
XSp Example: Rn-Pde9a-XMm	designed to cross detect with the species (Sp)
O# Example: Mm-Islr-O1	Alternative design targeting different regions of the same transcript or isoforms
CDS Example: Hs-SLC31A-CDS	Probe targets the protein-coding sequence only
EnEm	Probe targets exons n and m
En-Em	Probe targets region from exon n to exon m
Retired Nomenclature
tvn Example: Hs-LEPR-tv1	Designed to target transcript variant n
ORF Example: Hs-ACVRL1-ORF	Probe targets open reading frame
UTR Example: Hs-HTT-UTR-C3	Probe targets the untranslated region (non-protein-coding region) only
5UTR Example: Hs-GNRHR-5UTR	Probe targets the 5' untranslated region only
3UTR Example: Rn-Npy1r-3UTR	Probe targets the 3' untranslated region only
Pan Example: Pool	A mixture of multiple probe sets targeting multiple genes or transcripts

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