Importantly, accumulation of neurofilament light proteins (NFL) in the cerebrospinal fluid (CSF) which marks neuronal damage, is higher in AD patients that carry the APOE ε4 allele, but only if they do not carry the short poly-T variant of TOM40 associated with late onset AD, suggesting that this mitochondrial protein may be protective against the dose effect of APOE ε4 [47]. Here, APOE is linked to Alzheimer disease.