Mechanisms of Axonopathy in CMT1X

Charcot-Marie-Tooth disease (CMT) is the eponymous designation for inherited disorders characterized exclusively or predominantly by neuropathy. CMT affects approximately one in 2500 individuals worldwide. For the most part, mutations in genes expressed exclusively in Schwann cells, the myelinating cell of the PNS, produce demyelinating CMT. However, disability in all forms of CMT likely arises from axonal loss. Nonetheless, mechanisms of axonal loss in diseases caused by mutations in Schwann cells is not well understood. This is particularly highlighted in CMT1X, caused by mutations of GJB, the gene encoding connexin 32 (Cx32), a gap junction protein expressed in Schwann cells but not elsewhere in the peripheral nervous system. In spite of this Schwann cell localization, CMT1X is characterized by significant axonopathy, especially in its earliest stages. This application is a discovery-based proposal which will integrate data from Schwann cells, other peripheral nerve cells, and spinal motor neurons (Anterior Horn Cells, AHCs) and will provide us with insights into both motor neuron signaling pathways as well as peripheral nerve signaling pathways which are disrupted in in the absence of Cx32. There is currently a paucity of identified targets for ameliorating axonal loss in demyelinating CMT, and our results will likely identify therapeutic targets to preserve axonal function in patients with CMT. Thus, this work will form the basis for future hypothesis driven investigations to treat axonal loss, the underlying cause of morbidity in CMT1X and all forms of CMT. In Aim 1 we ask, “what are the alterations in gene expression that characterize the spinal motor neurons (anterior horn cells, AHCs) of CMT1X mice after onset of axonopathy but prior to demyelination and after onset of demyelination?” We will use the RiboTag approach in conjunction with ChAT-Cre to examine RNA expression from Anterior Horn Cells (AHCs) in the spinal cord of a Cx32 knockout mouse model of CMT1X (Cx32 KO) as well as WT and appropriate controls (ChAT-Cre or RiboTag alone) at two and six months of age. In Aim 2 we ask, “what are the alterations in gene expression that characterize the myelinating Schwann cells of CMT1X mouse nerve after onset of axonopathy but prior to demyelination and after onset of demyelination? To identify cell specific signaling pathways that contribute to the axonopathy of CMT1X we will use single nuclear RNA-seq to examine the transcriptome of the resident cells in the sciatic nerves of WT and Cx32KO at the same timepoints as Aim 1. In Aim 3 we ask, ”how are patterns of gene expression in anterior horn cell and peripheral nerve cell complement affected by an effective treatment of neuropathy in a CMT1X model mouse?” We will utilize cemdomespib to investigate the effects on the patterns of gene expression in AHCs and resident nerve cells from WT and Cx32KO mice using the same approaches outlined in Aims 1 and 2. Thus, this work will form the basis for future hypothesis driven investigations to treat axonal loss, the underlying cause of morbidity in CMT1X and all forms of CMT. Project Number: 1R21NS142944-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Neurological Disorders and Stroke (NINDS) | Principal Investigator: CHARLES ABRAMS | Institution: UNIVERSITY OF ILLINOIS AT CHICAGO, Chicago, IL | Award Amount: $200,413 | Activity Code: R21 | Study Section: Cellular and Molecular Biology of Glia Study Section[CMBG] View on NIH RePORTER: https://reporter.nih.gov/project-details/11304444