We recently identified mutations in the fukutin related protein (FKRP) gene in patients with congenital muscular dystrophy type 1C (MDC1C) and limb girdle muscular dystrophy type 2I (LGMD2I). The sarcolemma of these patients typically displays an immunocytochemical reduction of alpha-dystroglycan. In this report we extend these observations and report a clear correlation between the residual expression of alpha-dystroglycan and the phenotype. Three broad categories were identified. Patients at the severe end of the clinical spectrum (MDC1C) were compound heterozygote between a null allele and a missense mutation or carried two missense mutations and displayed a profound depletion of alpha-dystroglycan. Patients with LGMD with a Duchenne-like severity typically had a moderate reduction in alpha-dystroglycan and were compound heterozygotes between a common C826A (Leu276Ileu) FKRP mutation and either a missense or a nonsense mutation. Individuals with the milder form of LGMD2I were almost invariably homozygous for the Leu276Ile FKRP mutation and showed a variable but subtle alteration in alpha-dystroglycan immunolabeling. Our data therefore suggest a correlation between a reduction in alpha-dystroglycan, the mutation and the clinical phenotype in MDC1C and LGMD2I which supports the hypothesis that dystroglycan plays a central role in the pathogenesis of these disorders.

We evaluated coenzyme Q 10 (CoQ) levels in patients studied under suspicion of mitochondrial DNA depletion syndromes (MDS) (n=39). CoQ levels were quantified by HPLC, and the percentage of mtDNA depletion by quantitative real-time PCR. A high percentage of MDS patients presented with CoQ deficiency as compared to other mitochondrial patients (Mann-Whitney-U test: p= 0.001). Our findings suggest that MDS are frequently associated with CoQ deficiency, as a possible secondary consequence of disease pathophysiology. Assessment of muscle CoQ status seems advisable in MDS patients since the possibility of CoQ supplementation may then be considered as a candidate therapy. KeywordsMitochondrial DNA depletion syndrome; coenzyme Q 10 deficiency; mitochondrial disorders. AbbreviationsCoenzyme Q 10 (CoQ); mitochondrial DNA depletion syndromes (MDS); high pressure liquid chromatography (HPLC); mitochondrial DNA (mtDNA); mitochondrial respiratory chain (MRC); citrate synthase (CS);

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