C9orf72 and amyotrophic lateral sclerosis: Given that brain tissue analysis of C9orf72 mRNA expression levels has been limited to the frontal cortex [16, 22], we first sought to explore whether C9orf72 mRNA expression is similarly decreased in the frontal cortex of our cohort of patients, and to evaluate whether a reduction is also observed in the cerebellum, another brain region affected in c9FTD/ALS [34].