Genetic Rescue of Mitochondrial and Skeletal Muscle Impairment in an Induced Pluripotent Stem Cells Model of Coenzyme Q10 Deficiency

Coenzyme Q(10) (CoQ(10)) plays a crucial role in mitochondria as an electron carrier within the mitochondrial respiratory chain (MRC) and is an essential antioxidant. Mutations in genes responsible for CoQ(10) biosynthesis (COQ genes) cause primary CoQ(10) deficiency, a rare and heterogeneous mitochondrial disorder with no clear genotype-phenotype association, mainly affecting tissues with high-energy demand including brain and skeletal muscle (SkM). Here, we report a four-year-old girl diagnosed with minor mental retardation and lethal rhabdomyolysis harboring a heterozygous mutation (c. 483G > C (E161D)) in COQ4. The patient's fibroblasts showed a decrease in [CoQ(10)], CoQ(10) biosynthesis, MRC activity affecting complexes I/II+III, and respiration defects. Bona fide induced pluripotent stem cell (iPSCs) lines carrying the COQ4 mutation (CQ4-iPSCs) were generated, characterized and genetically edited using the CRISPRCas9 system (CQ4 ed -iPSCs). Extensive differentiation and metabolic assays of control-iPSCs, CQ4iPSCs and CQ4 ed -iPSCs demonstrated a genotype association, reproducing the disease phenotype. The COQ4 mutation in iPSC was associated with CoQ(10) deficiency, metabolic dysfunction, and respiration defects. iPSC differentiation into SkM was compromised, and the resulting SkM also displayed respiration defects. Remarkably, iPSC differentiation in dopaminergic or motor neurons was unaffected. This study offers an unprecedented iPSC model recapitulating CoQ(10) deficiency-associated functional and metabolic phenotypes caused by COQ4 mutation. 0