A novel mitochondrial DNA mutation and a mutation in the Notch3 gene in a patient with myopathy and CADASIL

Abstract

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is characterized by cerebral symptoms, but peripheral nerve or muscle involvement has not been reported. We describe a patient who had a stereotypic clinical presentation of CADASIL and, in addition, myopathy with ragged-red fibers, suggesting a mitochondrial disorder. Therefore we determined the nucleotide sequence in the entire coding region of the patient's mtDNA by conformation-sensitive gel electrophoresis and sequencing. Sequence of the exon 4 in the Notch3 gene was determined in a similar fashion. We found that the patient had myopathy with ragged-red fibers, and ultrastructural examination revealed mitochondrial aberrations. CADASIL was due to an R133C mutation in Notch3; in addition, we found a novel mutation 5650G>A in the tRNAAla gene in mtDNA. The mutation was heteroplasmic, with the proportions of the mutant genome being 99% in muscle, 96% in the buccal epithelium, 95% in the skin, and 65% in the blood. The absence of the mutation in a maternal cousin four times removed indicated that it was new in the pedigree. We suggest that the mtDNA mutation is pathogenic, as it was associated with a relevant clinical phenotype, it was not found among controls, and it altered a structurally important segment in the amino acid acceptor stem in the tRNAAla. Furthermore, its absence in nine patients from five families with R133C suggests that its relationship with the Notch3 mutation is coincidental.

Role of mitochondrial dysfunction in cancer progression

“…32 The G5650A transition was reported at a high level of heteroplasmy in the muscle and blood of a patient with a stereotypic clinical presentation of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and myopathy with ragged-red fibers. 31 The mtDNA mutation was also found in a family with a predominantly proximal myopathy and was associated with a large number of cytochrome c oxidase-deficient fibers and a marked decrease in the activities of both Complex I and Complex IV. 23 The 7472insC was identified in a gastric cancer patient 27 and was a ''C'' nucleotide insertion in the mononucleotide repeat of a poly-C sequence at np 7466-7472 in mtDNA, which could alter the structure of the TcC loop in the clover leaf secondary structure of tRNA Ser(UCN) .…”

“…20 Clinically, the two mutations have been previously reported to be associated with distinct mitochondrial disorders. 23,31,32 The T1659C transition was found at a very high level of heteroplasmy in the blood, and skeletal muscle from a young girl with learning difficulties, hemiplegia, and a movement disorder, as well as an increased lactate level in the cerebrospinal fluid. 32 The G5650A transition was reported at a high level of heteroplasmy in the muscle and blood of a patient with a stereotypic clinical presentation of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and myopathy with ragged-red fibers.…”

Mitochondrial tRNA mutations may be infrequent in hepatocellular carcinoma patients

“…Of these, T1659C, G5650A, and C15975T have been reported to be associated with mitochondrial diseases and may be classified as "definitely pathogenic" (Finnilä et al, 2001;Blakely et al, 2004;McFarland et al, 2008;Da Pozzo et al, 2009). At the molecular level, these mutations decrease the stability and aminoacylation ability of the corresponding tRNAs.…”

“…Moreover, the tRNA Ala G5650A mutation has been reported in a patient suffering cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (Finnilä et al, 2001;McFarland et al, 2008). This sequence variation occurs at the site of tRNA Ala recognized by mitochondrial alanyl-tRNA synthetase, which serves a vital function in tRNA Ala aminoacylation, an essential prerequisite for protein translation (Park and Schimmel, 1988).…”

Mitochondrial tRNA Mutations: Clinical and Functional Perturbations

“…171 This mutation has also observed as heteroplasmic in patients with CADASIL, a cerebral autosomal dominant arteriopathy with subcortical infracts and leukoencephalopathy. 172 Some of the CADASIL patients also shared an R133C mutation in Noch3 gene, although in nine patients C5650T was the only mutation. 173 Exercise intolerance and myoglobinuria.…”