Abstract
Background: The hexanucleotide repeat expansion in intron 1 of the C9orf72 gene is recognized as the most common genetic cause of frontotemporal dementia (FTD). There are overlapping clinical and pathological characteristics between FTD and Parkinsonism syndrome, and some FTD patients may present with Parkinsonism. The aim of this study was to analyze the hexanucleotide repeat numbers of C9orf72 gene in a mixed Taiwanese cohort with FTD, Parkinsonism syndrome, Parkinson’s disease (PD), and Alzheimer’s dementia (AD).Method: The number of hexanucleotide repeats was estimated in a total of 482 patients with mixed neurodegenerative disorders and 485 control subjects, using a two-step repeat-primed polymerase chain reaction-based genotyping strategy. The individual groups of patients included patients with Parkinsonism syndrome (n = 95), familial PD (n = 109), young-onset PD (n = 201), FTD (n = 9), sporadic AD (n = 61), and early-onset AD (n = 7).Results: We did not identify any pathogenic repeats (>30 repeats) of C9orf72 in either the patients or control subjects. However, we found one young-onset PD patient and one control subject that each had an intermediate number of repeats (25 and 21 repeats, respectively). The clinical phenotype of the young-onset PD in this patient was similar to typical idiopathic PD without additional features, and the patient responded well to levodopa treatment.Conclusion: The repeat expansion in C9orf72 is not a common cause of PD, Parkinsonism syndrome, or dementia in our population. Further studies are needed to investigate the clinical and biological significance of intermediate repeats in C9orf72.
Highlights
A massive expansion of the GGGGCC hexanucleotide repeat in the intron between non-coding exons 1a and 1b of the chromosome 9 open reading frame 72 (C9orf72) gene was recently found to be a major genetic cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) [1, 2]
We found one young-onset Parkinson’s disease (PD) patient and one control subject that each had an intermediate number of repeats (25 and 21 repeats, respectively).The clinical phenotype of the young-onset PD in this patient was similar to typical idiopathic PD without additional features, and the patient responded well to levodopa treatment
Given the clinical and pathological overlaps between FTD, Parkinsonism syndrome, PD, and Alzheimer’s dementia (AD), the aim of this study was to determine whether the abnormal C9orf72 hexanucleotide repeat expansions found in FTD patients is associated with these other neurodegenerative disorders in a Taiwanese population
Summary
A massive expansion of the GGGGCC hexanucleotide repeat in the intron between non-coding exons 1a and 1b of the chromosome 9 open reading frame 72 (C9orf72) gene was recently found to be a major genetic cause of familial frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) [1, 2]. In addition to FTD and ALS, other features in patients carrying the C9orf mutation can include isolated Parkinsonian movement disorder, memory impairment, and signs of cerebellar dysfunction [4] These symptoms tend to accumulate and phenotypes may converge with disease progression. Given the clinical and pathological overlaps between FTD, Parkinsonism syndrome, PD, and Alzheimer’s dementia (AD), the aim of this study was to determine whether the abnormal C9orf hexanucleotide repeat expansions found in FTD patients is associated with these other neurodegenerative disorders in a Taiwanese population. There are overlapping clinical and pathological characteristics between FTD and Parkinsonism syndrome, and some FTD patients may present with Parkinsonism.The aim of this study was to analyze the hexanucleotide repeat numbers of C9orf gene in a mixed Taiwanese cohort with FTD, Parkinsonism syndrome, Parkinson’s disease (PD), and Alzheimer’s dementia (AD)
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