LRRK2 and Parkinson disease: When the investigators used adenovirus to insert the LRRK2 G2019S mutation into wild-type hESCs, they found that NSCs from the mutant hESCs – but not NSCs from the wild-type hESCs – displayed the same nuclear and differentiation defects as the PD iPSCs, thereby establishing the necessity and sufficiency of the G2019S mutation for the disease phenotypes.