The size of large repeating arrays of G4C2 in the chromosome 9 open reading frame 72 (C9orf72) is correlated with age of onset of C9 amyotrophic lateral sclerosis (C9ALS).
Why this matters
C9ALS is characterized by a hexanucleotide (G4C2) repeat expansion in C9orf72 and is the largest genetic subgroup identified in ALS, responsible for 39% of familial and 7% of non-familial or singleton amyotrophic lateral sclerosis (SALS).
The same mutation also causes frontotemporal lobar degeneration (FTLD).
These data will inform future clinical trial design by providing an evidence-based account of the natural history and pathology of C9ALS.