C9orf72 and amyotrophic lateral sclerosis: Recognition of a hexanucleotide repeat expansion (HRE) in the C9orf72 gene as the most common cause of the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) has opened avenues for understanding the molecular mechanisms of a number of neurological diseases [1, 2].