Realizing the gains and losses in C9ORF72 ALS/FTD

At the heart of C9ORF72-related amyotrophic lateral sclerosis and frontotemporal dementia (ALS /FTD) research lies the mechanistic question of whether disease is caused by toxic gain of function related to the repeat expansion, loss of endogenous C9ORF72 expression, or both. New findings provide insights to this question.