After permutation testing (p-value < 0.05), average mRNA expression from roughly 20% of all C9orf72-co-expressed genes (n = 2,120 genes) significantly correlated with average cortical thickness in symptomatic C9orf72 HRE carriers, including C9orf72 and 7 out of the 54 ALS/FTD genes: TARDBP, ATXN2, NEFH, SETX, PFN1, VAPB, and UNC13A (Figure 5). Here, C9orf72 is linked to frontotemporal dementia.