NEFL and amyotrophic lateral sclerosis: This was demonstrated in rodents103 and in retinal ganglion cells.104 NfL is, however, degraded by the calcium protease calpain,105,106 and degradation is influenced by phosphorylation state.106 Protease activity and phosphorylation are important in axonal degradation, but there is no indication as to the proportion of full-length and other NfL species in CSF and blood in ALS.