Since the hexanucleotide expansion in C9ORF72 is also causative for frontotemporal lobar degeneration (FTLD), accounting for about 25% of familial and 5% of sporadic cases [24], we decided to expand our initial observations in C9-ALS iMNs to cortical neurons differentiated from the same iPSC lines as above using the previously published i3 method [25]. Here, C9 is linked to frontotemporal dementia.