GRN haploinsufficiency is thought to underlie GRN-associated FTD pathogenesis, with heterozygous GRN mutations resulting in a loss-of-function, owing to (1) mutant mRNA clearance by nonsense-mediated decay, (2) prevention of mRNA translation due to missense or splice site mutations of the initiator methionine codon and (3) production of non-functional and unstable protein (81, 86). The gene discussed is GRN; the disease is frontotemporal dementia.