Charcot–Marie–tooth disease causing mutation (p.R158H) in pyruvate dehydrogenase kinase 3 (PDK3) affects synaptic transmission, ATP production and causes neurodegeneration in a CMTX6C. elegansmodel

Abstract

Charcot–Marie-Tooth (CMT) is a commonly inherited, non-fatal neurodegenerative disorder that affects sensory and motor neurons in patients. More than 90 genes are known to cause axonal and demyelinating forms of CMT. The p.R158H mutation in the pyruvate dehydrogenase kinase 3 (PDK3) gene is the genetic cause for an X linked form of axonal CMT (CMTX6). In vitro studies using patient fibroblasts and iPSC-derived motor neurons have shown that this mutation causes deficits in energy metabolism and mitochondrial function. Animal models that recapitulate pathogenic in vivo events in patients are crucial for investigating mechanisms of axonal degeneration and developing therapies for CMT. We have developed a C. elegans model of CMTX6 by knocking-in the p.R158H mutation in pdhk-2, the ortholog of PDK3. In addition, we have developed animal models overexpressing the wild type and mutant form of human PDK3 specifically in the GABAergic motor neurons of C. elegans. CMTX6 mutants generated in this study exhibit synaptic transmission deficits, locomotion defects and show signs of progressive neurodegeneration. Furthermore, the CMTX6 in vivo models display energy deficits that recapitulate the phenotype observed in patient fibroblasts and iPSC-derived motor neurons. Our CMTX6 animals represent the first in vivo model for this form of CMT and have provided novel insights into the cellular function and metabolic pathways perturbed by the p.R158H mutation, all the while closely replicating the clinical presentation observed in CMTX6 patients.

Novel gene-intergenic fusion involving ubiquitin E3 ligase UBE3C causes distal hereditary motor neuropathy: A new mechanism for motor neuron degeneration

“…81 Using this method, we have previously successfully identified synaptic transmission deficits in a CMT model of C. elegans. 82 UBE3C-IF animals displayed resistance to aldicarb induced paralysis when compared to control animals (Fig. 8A).…”

Novel gene–intergenic fusion involving ubiquitin E3 ligase UBE3C causes distal hereditary motor neuropathy

“… 84 Using this method, we have previously successfully identified synaptic transmission deficits in a CMT model of C. elegans. 85 UBE3C-IF animals displayed resistance to aldicarb-induced paralysis when compared to control animals ( Fig. 7A ).…”

Therapeutic Potential of Vitamins in Charcot-Marie-Tooth Disease with the Compromised Status of the Vitamin-Dependent Processes

“…Metabolic characteristics of fibroblasts and iPSC-derived motor neurons of the patients reveal failures in energy production and mitochondrial function. In vivo models where the R158H-substituted PDK3 ortholog, known as PDHK2 in C. elegans, is knocked-in, or the wild-type and mutated PDK3 are overexpressed in the GABA-ergic motor neurons, recapitulate deficits in mitochondrial function and synaptic neurotransmission, observed in the cellular studies [13]. Besides, the models reveal such characteristics of CMT disease as the locomotion defects and signs of progressive neurodegeneration.…”

“…Approximately 1000 mutations in 90 different genes are known to cause CMT disease, with most of the mutations affecting cytoskeleton or axonal trafficking [13,14]. Genetic impairments in the mitochondrial proteins represent the most direct pathway to mitochondrial insufficiency associated with CMT disease.…”