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Reduced-penetrance Huntington's disease-causing alleles with 39 CAG trinucleotide repeats could be a genetic factor
Kang-Yang Jih1,2,3, Kuan-Lin Lai1,3,4, Kon-Ping Lin1,3
1Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan, ROC.
Insights
A rare HTT gene expansion (40+ CAG repeats) is linked to ALS. In a Taiwanese cohort, one patient with 39 repeats showed ALS susceptibility, suggesting a potential genetic factor.
Area of Science:
- Neurogenetics
- Molecular Biology
Background:
- Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease.
- Expanded Huntingtin (HTT) alleles (≥40 CAG repeats) are a rare cause of frontotemporal dementia and ALS spectrum disorders.
Background:
Expanded HTT alleles with 40 or more CAG repeats were recently found to be a rare cause of frontotemporal dementia and amyotrophic lateral sclerosis (ALS) spectrum diseases. The aim of this study was to investigate the role of HTT repeat expansions in a Taiwanese cohort with ALS.
Methods:
We analyzed the numbers of CAG repeats in exon 1 of HTT in a cohort of 410 Taiwanese patients with ALS and 1514 control individuals by utilizing polymerase chain reaction and amplicon fragment length analysis.
Results:
Only one of the 410 ALS patients carried a reduced-penetrance HD-causing allele with 39 CAG repeats, and none had an expanded HTT CAG repeats ≥40. The patient presented with rapidly progressive bulbar-onset ALS with disease onset at the age of 64 years. He had neither chorea nor cognitive impairment. He had a family history of chorea, but no other family member manifested with ALS. None of the 1514 control individuals carried an HTT expanded allele with CAG repeats larger than 37 repeats.
Conclusion:
The HTT allele with 39 CAG repeats could be a genetic factor linked to ALS susceptibility.
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