C2 and amyotrophic lateral sclerosis: Similarly, PCA using most the 12 most differentially abundant proteins (C2 CD5, CHI3L1, CHIT1, SLC39 A10, XXYLT1, TGFBR3, SORCS3, HYOU1, MINPP1, CHI3L2, SERPINA3, and PCDH11X) effectively distinguished asymptomatic from symptomatic ALS individuals (Fig. 7b).