The clinical heterogeneity of coenzyme Q10 deficiency results from genotypic differences in the Coq9 gene

Authors
Luna-Sánchez M, Díaz-Casado E, Barca E, Tejada MÁ, Montilla-García Á, Cobos EJ, Escames G, Acuña-Castroviejo D, Quinzii CM, López LC

Lab
Departamento de Fisiología, Facultad de Medicina, Universidad de Granada, Granada, Spain Centro de Investigación Biomédica, Instituto de Biotecnología, Parque Tecnológico de Ciencias de la Salud, Granada, Spain.

Journal
EMBO Mol Med.

Abstract
Primary coenzyme Q10 (CoQ10) deficiency is due to mutations in genes involved in CoQ biosynthesis. The disease has been associated with five major phenotypes, but a genotype-phenotype correlation is unclear. Here, we compare two mouse models with a genetic modification in Coq9 gene (Coq9(Q95X) and Coq9(R239X)), and their responses to 2,4-dihydroxybenzoic acid (2,4-diHB). Coq9(R239X) mice manifest severe widespread CoQ deficiency associated with fatal encephalomyopathy and respond to 2,4-diHB increasing CoQ levels. In contrast, Coq9(Q95X) mice exhibit mild CoQ deficiency manifesting with reduction in CI+III activity and mitochondrial respiration in skeletal muscle, and late-onset mild mitochondrial myopathy, which does not respond to 2,4-diHB. We show that these differences are due to the levels of COQ biosynthetic proteins, suggesting that the presence of a truncated version of COQ9 protein in Coq9(R239X) mice destabilizes the CoQ multiprotein complex. Our study points out the importance of the multiprotein complex for CoQ biosynthesis in mammals, which may provide new insights to understand the genotype-phenotype heterogeneity associated with human CoQ deficiency and may have a potential impact on the treatment of this mitochondrial disorder.

BIOSEB Instruments Used:
Spontaneous activity wheels (BIO-ACTIVW-M)