Fig. 4

Optimised set of MN-specific hypomethylated genomic regions is not detectable in ALS patient plasma cfDNA. (A) We used a synthetic mix of WGBS reads from non-diseased plasma cfDNA together with spike-in reads from iPSC-derived MN to determine the optimum set of MN-specific regions for detection in ALS patient biosamples. (B) At spike-ins of 1–10% there is a linear relationship between spike-in and predicted MN DNA concentrations for all sets of MN-specific methylation blocks; p < 0.02, adjusted r² > 0.998, Pearson’s product moment correlation coefficient. (C) At spike-ins ≲ 1% it is possible to detect reads derived from MN-specific regions but the detection probability is < 0.5. (D) MN-specific DNA is not detectable within ALS patient plasma