Energy metabolism and mitochondrial defects in X-linked Charcot-Marie-Tooth (CMTX6) iPSC-derived motor neurons with...

Area of Science:

• Neuroscience
• Genetics
• Cell Biology

Background:

• Charcot-Marie-Tooth (CMT) encompasses genetically diverse peripheral neuropathies.
• X-linked CMT (CMTX6) is linked to a specific mutation (p.R158H) in the pyruvate dehydrogenase kinase 3 (PDK3) gene.
• This mutation leads to PDK3 hyperactivity, PDC hyperphosphorylation, reduced activity, and impaired ATP production.

Purpose of the Study:

• To generate and characterize induced pluripotent stem cells (iPSCs) from CMTX6 patients.
• To validate the role of the PDK3 mutation in disease pathogenesis using iPSCs and patient-derived motor neurons.
• To establish a cellular model for screening potential CMTX6 therapeutics.

Main Methods:

• Reprogramming CMTX6 fibroblasts into iPSCs (iPSC^CMTX6) and creating isogenic controls (iPSC^isogenic).
• Genetic correction of the p.R158H mutation in iPSCs.
• Differentiation of iPSCs into patient-derived motor neurons (MN^CMTX6).
• Assessment of PDC phosphorylation, energy metabolism, mitochondrial function, and mitochondrial trafficking in MN^CMTX6.
• Treatment of MN^CMTX6 with a PDK inhibitor.

Main Results:

• Genetic correction of the p.R158H mutation in iPSCs fully reversed the CMTX6 cellular phenotype.
• MN^CMTX6 exhibited hyperphosphorylated PDC, impaired energy metabolism, and mitochondrial deficits, including slower trafficking.
• PDK inhibitor treatment normalized PDC phosphorylation and ameliorated functional deficits in MN^CMTX6.

Conclusions:

• The p.R158H mutation in PDK3 is causative for CMTX6, leading to mitochondrial dysfunction via PDC hyperphosphorylation.
• Patient-derived iPSCs and motor neurons accurately model CMTX6.
• This cellular model is suitable for identifying therapeutic compounds targeting PDK activity for CMTX6 treatment.