C9orf72 and frontotemporal dementia: Nevertheless, it is intriguing to note that in addition to the association of RAB39B with aSyn and Aβ, as observed here and elsewhere (14, 35), the protein has also been implicated in huntingtin protein homeostasis (39) and has a clear functional dependency on C9orf72, which is associated with ALS and FTD (9, 26, 37).