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C9orf72 hexanucleotide repeat expansions as the causative mutation for chromosome 9p21-linked amyotrophic lateral sclerosis and frontotemporal dementia.

OBJECTIVE
To further assess the presence of a large hexanucleotide repeat expansion in the first intron of the C9orf72 gene identified as the genetic cause of chromosome 9p21-linked amyotrophic lateral sclerosis and frontotemporal dementia (c9ALS/FTD) in 4 unrelated families with a conclusive linkage to c9ALS/FTD.


DESIGN
A repeat-primed polymerase chain reaction assay.


SETTING
Academic research.


PARTICIPANTS
Affected and unaffected individuals from 4 ALS/FTD families.


MAIN OUTCOME MEASURE
The amplified C9orf72 repeat expansion.


RESULTS
We show that the repeat is expanded in and segregated perfectly with the disease in these 4 pedigrees.


CONCLUSION
Our findings further confirm the C9orf72 hexanucleotide repeat expansion as the causative mutation for c9ALS/FTD and strengthen the hypothesis that ALS and FTD belong to the same disease spectrum.