Additionally, three humanised mouse models representing AD, tauopathies, and α-synucleinopathies including PD were used to identify neurofilament light chain (NfL) as a marker of neurodegenerative disease progression (Bacioglu et al. 2016), which has recently been translated to patient studies demonstrating serum NfL as a presymptomatic marker of familial AD (Preische et al. 2019). The gene discussed is NEFL; the disease is Parkinson disease.