These misfolded proteins include amyloid-β protein (Aβ) and tau in Alzheimer’s disease (AD); α-synuclein and synphilin 1 in Parkinson’s disease (PD); polyglutamine (polyQ)-expanded huntingtin in Huntington’s disease; transactive response DNA binding protein 43 (TDP-43) and copper-zinc superoxide dismutase 1 in motor neuron disease (MND); and tau, TDP-43 and fused in sarcoma in frontotemporal lobar degeneration (FTLD). Here, HTT is linked to Parkinson disease.