These screens have been carried out in experimental models of frontotemporal dementia (FTD) (i.e., expressing hexanucleotide repeat expansion in the C9ORF72 gene), the second most common dementia after AD [125] that exhibit alterations in the repressive marks H3K9me3, H3K9me27 and DNA methylation in neurons and astrocytes [126,127,128,129]. The gene discussed is C9orf72; the disease is frontotemporal dementia.