Key Features and Values
- Reliable and reproducible method for high-resolution genotyping of hexanucleotide repeat expansions in the C9orf72 gene
The AmplideX PCR/CE C9orf72 Kit (RUO) is used to PCR-amplify the C9orf72 hexanucleotide fragment from purified genomic DNA using a three-primer G4C2-Repeat Primed (RP)-PCR configuration, followed by fragment sizing on an Applied Biosystems Genetic Analyzer. The PCR reagents include gene-specific and G4C2 repeat primers, diluent, a polymerase mix and buffer for amplification of the (G4C2)n repeat region in the C9orf72 gene, and a ROX 1000 Size Ladder for sizing by CE. The size of the PCR products are converted to the number of G4C2 repeats using size and mobility conversion factors.
Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are neurodegenerative disorders that are now believed to be part of the same clinical continuum of diseases. FTD is a progressive dementia syndrome associated with atrophy of the frontal and anterior temporal lobes, which may result in changes in personality, decision-making skills, impulse-control, behavior, and language but leave memory and perception relatively unaffected. In people under 65 years of age, it is the second most common form of dementia after Alzheimer disease. ALS is characterized by a loss of upper (i.e., brain) and lower (i.e., brainstem and spinal cord) motor neurons, which leads to progressive weakness of the voluntary muscles. Clinical studies have shown that approximately 15% of patients with FTD also have ALS. In addition, while approximately 15% of patients with ALS have FTD, up to 50% of patients with ALS also exhibit frontal lobe impairment but do not meet strict criteria for FTD.
At the molecular level, an expansion of a hexanucleotide repeat element (G4C2) in intron 1 of the Chromosome 9 open reading frame 72 gene (C9orf72; NM_001256054.2) has been linked to FTD and ALS. Unaffected individuals have <20 hexanucleotide repeats, while affected individuals have >30 repeats and often >1,000 repeats. The range of 20-30 repeats is considered to be an intermediate range with no clinical evidence of disease manifestation. The expansion appears in approximately 25% of familial FTD patients and 20-67% of familial ALS patients depending on the population studied, making this the most prevalent genetic mutation in both diseases. The expansion also appears in approximately 6% of sporadic FTD patients and 7% of sporadic ALS patients. In addition, intermediate repeat lengths (20-30 repeats) have been reported to be a significant risk factor for Parkinson Disease (PD).