CHIT1 and amyotrophic lateral sclerosis: We also did not observe pathological changes with chitotriosidase (CHIT1), a protein recently implicated in ALS pathogenesis.28 These results are consistent with our CSF filtration findings, as all of these proteins are smaller than 300 kDa and are therefore present in the 300 kDa filtrate which had no effect upon intrathecal administration in mice.