FTD-GRN is caused by heterozygous mutations, while individuals homozygous for pathogenic GRN mutations develop neuronal ceroid lipofuscinosis instead of FTD [22, 23], making Grn+/− mice a closer genetic model of human FTD-GRN than Grn−/− mice. This evidence concerns the gene GRN and neuronal ceroid lipofuscinosis.