Given the report that C9orf72:SMCR8 is also a GAP for RAB8A and RAB11A20, the question as to what are the physiological substrates of C9orf72:SMCR8 has become important in C9ORF72, ALS, and FTD research39,40. This evidence concerns the gene SMCR8 and frontotemporal dementia.