If this localized interaction between 4R tau and alpha-synuclein was deleterious, it could explain why the H1 MAPT haplotype, associated with increased 4R tau (Caffrey et al., 2006; Myers et al., 2007), is a risk factor for Parkinson’s disease (Satake et al., 2009; Simón-Sánchez et al., 2009). The gene discussed is MAPT; the disease is Parkinson disease.