Subtler phenotypes in later-onset disorders such as Parkinson's disease (PD) have also been revealed by correction of disease-causing variants; Reinhardt et al. demonstrated that cellular phenotypes such as neurite outgrowth, abnormal autophagy, and tau and α-synuclein accumulation were LRRK2-dependent in familial PD (Reinhardt et al., 2013). Here, MAPT is linked to Parkinson disease.