Fig. 7

Knockout of C9orf72 seems to negatively affect lysosome number, but does not affect lysosome morphology. a Fluorescent microscopy images of 40-day-old C9 KO and isogenic control MNs labeled with SiR-Lysosome, a dye that selectively labels Cathepsin D-positive lysosomes. Scale bar = 50 µm. b, c Quantification of the SiR-Lysosome puncta number (b) and fluorescent intensity per cell (c) from the images shown in (a); each dot represents one confocal image that was analyzed (n = 60 for all conditions in (b) and n = 80 for all conditions in (c)). d Representative TEM images from 40-day old MNs used to quantify the size of lysosomes/late endosome (indicated by black arrowheads). Mitochondria (M), Golgi complex (GC), Nucleus (N) and the endoplasmic reticulum (ER) are marked on the images. e, f Relative frequency distribution (e) and quantification (f) of the lysosomal circumference measured from TEM images as shown in (d); each dot represents a lysosome that was measured (CTRL, n = 692; C9 KO, n = 765). Data represent mean ± SEM; data are pooled from three-four independent differentiations. Statistical significance was assessed by unpaired t-test (b, c) or Mann–Whitney U test (e); *p < 0.05, **p < 0.01