Mutant COQ2 in Multiple-System Atrophy

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To the Editor: Tsuji and colleagues (July 18 issue) 1 report that variants in the gene encoding coenzyme Q 2 (COQ2) increase the risk of multiple-system atrophy.They observed homozygous COQ2 variants encoding the substitutions M78V and V343A in a consanguineous Japanese family with multiple-system atrophy subtype P and noted an association between V343A and sporadic multiple-system atrophy (minor-allele frequency [MAF], 4.8% of cases vs. 1.6% of controls; odds ratio, 3.05; 95% confidence interval, 1.65 to 5.85).However, the authors erroneously labeled human COQ2 variability from the fourth ATG start codon in exon 1, which encodes the smallest protein isoform and does not functionally complement the yeast coq2-null mutant.2 On the basis of the National Center for Biotechnology Information (NCBI) Reference Sequence (NM_015697.7),M78V should be labeled COQ2 c.382A→G (p.M128V) and V343A should be labeled c.1178T→C (p.V393A).We sequenced COQ2 in 299 Korean persons with multiple-system atrophy and 365 unaffected Korean persons and observed heterozygous COQ2 c.320G→C (encoding p.S107T) and c.382A→T (encoding p.M128R) in 2 patients with sporadic multiple-system atrophy; COQ2 c.1178T→C (p.V393A) was not associated with multiple-system atrophy (MAF, 2.7% of cases vs. 2.6% of controls).It is a challenge to reconcile recessive linkage of homozygous COQ2 mutations in familial multiple-system atrophy with a heterozygous, presumably dominant-negative association in sporadic multiple-system atrophy.Respectfully, we suggest that Tsuji and colleagues reconsider whether variations in COQ2 represent a risk factor for multiple-system atrophy.Genomic multiplications of the SNCA 6.4-Mb locus telomeric to COQ2 have previously been implicated in parkinsonism and multiple-system atrophy 3 ; copy number analysis of linked loci, or genomewide analysis, should be considered.

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