MT-ND2 and amyotrophic lateral sclerosis: For apparent deletions involving ND4 (Figure 4A), samples with high deletion abundances (i.e, ND4/ND2 ratios < 0.2) were distributed in CTL samples across ~2 orders of magnitude of ND2 levels, but were both much more abundant and distributed across ~5 orders of magnitude of ND2 levels in the ALS population.