Affiliations: Department of Neurology, Columbia University
Medical Center, New York, NY, USA
Note: [] Address for correspondence: Dr. Michio Hirano, Department of
Neurology, Columbia University Medical Center, 1150 St. Nicholas Ave., Russ
Berrie Medical Sciences Pavilion, Room 317, New York, NY 10032, USA. E-mail:
mh29@columbia.edu
Abstract: Coenzyme Q_{10} (CoQ_{10} or
ubiquinone) is a lipid-soluble component of virtually all cell membranes and
has multiple metabolic functions. A major function of
CoQ_{10} is to transport electrons from complexes I and II
to complex III in the respiratory chain which resides in the mitochondrial
inner membrane. Deficiencies of CoQ_{10} (MIM 607426) have
been associated with four major clinical phenotypes: 1) encephalomyopathy
characterized by a triad of recurrent myoglobinuria, brain involvement, and
ragged-red fibers; 2) infantile multisystemic disease typically with prominent
nephropathy and encephalopathy; 3) cerebellar ataxia with marked cerebellar
atrophy; and 4) pure myopathy. Primary CoQ_{10} deficiencies
due to mutations in ubiquinone biosynthetic genes (COQ2, PDSS1, PDSS2,
and ADCK3 [CABC1]) have been identified in patients with the
infantile multisystemic and cerebellar ataxic phenotypes. In contrast,
secondary CoQ_{10} deficiencies, due to mutations in genes
not directly related to ubiquinone biosynthesis (APTX, ETFDH, and
BRAF), have been identified in patients with cerebellar ataxia, pure myopathy,
and cardiofaciocutaneous syndrome. In many patients with
CoQ_{10} deficiencies, the causative molecular genetic
defects remain unknown; therefore, it is likely that mutations in additional
genes will be identified as causes of CoQ_{10}
deficiencies.
Journal: BioFactors, vol. 32, no. 1-4, pp. 113-118, 2008
