Haploinsufficiency of COQ4 causes coenzyme Q10 deficiency.


BACKGROUND COQ4 encodes a protein that organises the multienzyme complex for the synthesis of coenzyme Q(10) (CoQ(10)). A 3.9 Mb deletion of chromosome 9q34.13 was identified in a 3-year-old boy with mental retardation, encephalomyopathy and dysmorphic features. Because the deletion encompassed COQ4, the patient was screened for CoQ(10) deficiency. METHODS A complete molecular and biochemical characterisation of the patient's fibroblasts and of a yeast model were performed. RESULTS The study found reduced COQ4 expression (48% of controls), CoQ(10) content and biosynthetic rate (44% and 43% of controls), and activities of respiratory chain complex II+III. Cells displayed a growth defect that was corrected by the addition of CoQ(10) to the culture medium. Knockdown of COQ4 in HeLa cells also resulted in a reduction of CoQ(10.) Diploid yeast haploinsufficient for COQ4 displayed similar CoQ deficiency. Haploinsufficency of other genes involved in CoQ(10) biosynthesis does not cause CoQ deficiency, underscoring the critical role of COQ4. Oral CoQ(10) supplementation resulted in a significant improvement of neuromuscular symptoms, which reappeared after supplementation was temporarily discontinued. CONCLUSION Mutations of COQ4 should be searched for in patients with CoQ(10) deficiency and encephalomyopathy; patients with genomic rearrangements involving COQ4 should be screened for CoQ(10) deficiency, as they could benefit from supplementation.

DOI: 10.1136/jmedgenet-2011-100394

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@article{Salviati2012HaploinsufficiencyOC, title={Haploinsufficiency of COQ4 causes coenzyme Q10 deficiency.}, author={Leonardo Salviati and Eva Trevisson and Maria Angeles Rodriguez Hernandez and Alberto Casarin and Vanessa Pertegato and Mara Doimo and Matteo Cassina and Caterina Agosto and Mar{\'i}a Andrea Desbats and Geppo Sartori and Sabrina Sacconi and Luigi Memo and Orsetta Zuffardi and Rafael Artuch and Catarina M Quinzii and Salvatore Dimauro and Michio Hirano and Carlos Santos-Oca{\~n}a and Pl{\'a}cido Navas}, journal={Journal of medical genetics}, year={2012}, volume={49 3}, pages={187-91} }