Therefore, to directly generate iNSCs from PD fibroblasts with the LRRK2 (G2019S) mutation which are stably maintained, it is ideal to genetically treat the mLRRK2 fibroblasts during the process of TD, which may be achieved using a coupled TD and gene-correction approach (Figure 3(b), Step 1b). Here, LRRK2 is linked to Parkinson disease.