Despite the pronounced myelin loss, mature oligodendrocyte (ASPA-positive) cell density [33, 39] was not reduced in frontal white matter of FTD-GRN cases, and was 60% higher in FTD-C9orf72 compared to control cases (F = 6.15, p = 0.021) (Fig. 4G-H). Here, C9orf72 is linked to frontotemporal dementia.