PIWIL1 and Parkinson disease: However, as a proof-of-principle, PIWIL1 (PIWI-like protein 1) overexpression from a viral vector was sufficient to repress LINE-1 induced neurodegeneration of midbrain dopaminergic neurons during oxidative stress and in the En1± heterozygous mouse model of PD (Blaudin de Thé et al., 2018).