TARDBP and mild neurocognitive disorder: An alternative explanation of the role of C9ORF72 could be that the expansion acts as a risk factor for FTLD and MND, though does not drive the (TDP-43) pathological process directly, acting more as a ‘gatekeeper’ to disease, rendering the brain susceptible to the ‘development’ of all sporadic forms of FTLD-TDP, and sporadic forms of MND associated with TDP-43.