DPP6 and amyotrophic lateral sclerosis: While some of the most differentially abundant proteins were known ALS biomarkers (including CHIT1, CHI3L1, CHI3L2, FABP5, and UCHL1) [36, 37, 41], novel putative biomarkers were also identified (TMEM198, DPP6, C1QB, MERTK, WARS) as well as two ER related proteins (HYOU1 and XXYLT1).