Huntington's disease and mitochondrial DNA deletions: event or regular mechanism for mutant huntingtin protein and CAG repeats expansion?!
The mitochondrial DNA (mtDNA) may play an essential role in the pathogenesis of the respiratory chain complex activities in neurodegenerative disorders such as Huntington's disease (HD). Research studies were conducted to determine the possible levels of mitochondrial defect (deletion) in HD patients and consideration of interaction between the expanded Huntingtin gene as a nuclear gene and mitochondria as a cytoplasmic organelle. To determine mtDNA damage, we investigated deletions based in four areas of mitochondrial DNA, in a group of 60 Iranian patients clinically diagnosed with HD and 70 healthy controls. A total of 41 patients out of 60 had CAG expansion (group A). About 19 patients did not show expansion but had the clinical symptoms of HD (group B). MtDNA deletions were classified into four groups according to size; 9 kb, 7.5 kb, 7 kb, and 5 kb. We found one of the four-mtDNA deletions in at least 90% of samples. Multiple deletions have also been observed in 63% of HD patients. None of the normal control (group C) showed mtDNA deletions. The sizes or locations of the deletions did not show a clear correlation with expanded CAG repeat and age in our samples. The study presented evidence that HD patients had higher frequencies of mtDNA deletions in lymphocytes in comparison to the controls. It is thus proposed that CAG repeats instability and mutant Htt are causative factor in mtDNA damage.
Banoei
Mohammad Mehdi
MM
Department of Medical Genetics, National Institute of Genetic Engineering and Biotechnology, PO Box 14155-6343, Tehran, Iran.
Houshmand
Massoud
M
Panahi
Mehdi Shafa Shariat
MS
Shariati
Parvin
P
Rostami
Maryam
M
Manshadi
Masoumeh Dehghan
MD
Majidizadeh
Tayebeh
T
D000328:Adult; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics*; D008297:Male; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009687:Nuclear Proteins / Q000235:genetics*; D010641:Phenotype; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
D004272:DNA, Mitochondrial; C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins