Mutations of GEMIN5 are associated with coenzyme Q 10 deficiency: long-term follow-up after treatment.

GEMIN5 exerts key biological functions regulating pre-mRNAs intron removal to generate mature mRNAs. A series of patients were reported harboring mutations in GEMIN5. No treatments are currently available for this disease. We treated two of these patients with oral Coenzyme Q 10 (CoQ 10 ), which resulted in neurological improvements, although MRI abnormalities remained. Whole Exome Sequencing demonstrated compound heterozygosity at the GEMIN5 gene in both cases: Case one: p.Lys742* and p.Arg1016Cys; Case two: p.Arg1016Cys and p.Ser411Hisfs*6. Functional studies in fibroblasts revealed a decrease in CoQ 10 biosynthesis compared to controls. Supplementation with exogenous CoQ 10 restored it to control intracellular CoQ 10 levels. Mitochondrial function was compromised, as indicated by the decrease in oxygen consumption, restored by CoQ 10 supplementation. Transcriptomic analysis of GEMIN5 patients compared with controls showed general repression of genes involved in CoQ 10 biosynthesis. In the rigor mortis defective flies, CoQ 10 levels were decreased, and CoQ 10 supplementation led to an improvement in the adult climbing assay performance, a reduction in the number of motionless flies, and partial restoration of survival. Overall, we report the association between GEMIN5 dysfunction and CoQ 10 deficiency for the first time. This association opens the possibility of oral CoQ 10 therapy, which is safe and has no observed side effects after long-term therapy.