CMT2E is caused by dominant or recessive mutations in the Nefl gene which codes for the neurofilament protein L protein (NFL). This proposal takes advantage of mouse models of dominant and recessive CMT2E, one a heterozygous “knockin” of the N98S mutation and the other a homozygous “knockout” for the null mutation.
The mouse model of dominant CMT2E exhibits neurofilament accumulations in the cell soma and proximal axons and an absence of neurofilaments distally in axons of the peripheral nerves, whereas the mouse model of recessive CMT2E lacks neurofilaments throughout. Thus, we hypothesize that the mechanisms of dominant and recessive CMT2E disease converge on an absence of neurofilaments in myelinated axons of peripheral nerves, leading to reduced axon caliber and consequent impairment of nerve conduction. In recessive CMT2E, this arises because neurofilaments do not form in the absence of NFL. In dominant CMT2E, this could arise due to a defect in neurofilament assembly and/or transport.
The primary goal of this proposal is to evaluate a knockdown-and-replace gene therapy strategy for restoring neurofilaments to diseased neurons in dominant CMT2E, in which patients have one normal NFL allele and one mutant allele. We propose to knock down both the normal and mutant NFL using RNA interference and simultaneously rescue with normal NFL. The advantage of this approach is that it should be applicable to all CMT2E mutations, increasing the potential impact. The project involves a collaboration between the Brown, Burghes, Meyer and Arnold labs at Ohio State University which have complementary expertise in neurofilament biology, mouse genetics, gene therapy, viral vectors, neurodegenerative disease and electrophysiological assessments of neuromuscular function. We are currently screening lead candidates for RNAs that reduce NFL expression and testing an adeno-associated viral strategy to deliver NFL to neurons, with the ultimate goal to combine both into a single viral vector.
Stone, E.J., Kolb, S.J. & Brown, A. (2021). A review and analysis of the clinical literature on Charcot-Marie-Tooth disease caused by mutations in neurofilament protein L. Cytoskeleton, 78:97-110
Published: May 22, 2023