Using the 12 most differentially abundant proteins (CHI3L1, TMEM198, CHIT1, CHI3L2, HYOU1, XXYLT1, DPP6, C1QB, FABP5, MERTK, UCHL1, and WARS), PCA effectively distinguished ALS from controls (Fig. 7a). The gene discussed is MERTK; the disease is amyotrophic lateral sclerosis.