ATP7A and Parkinson disease: On the other hand, a comparative study on healthy-donor iPSC-derived neurons carrying either the H1/H1 or the H2/H2 MAPT haplotype did not reveal major haplotype-specific differences in tau expression but it showed significantly higher levels of conformationally altered MC1-positive insoluble tau in neurons carrying the H2/H2 haplotype, while neurons with the H1/H1 haplotype demonstrated an increased expression of alpha-synuclein that accumulates in neurons in PD (Strauss et al., 2021).