PTBP1 and Parkinson disease: Given that Ptbp1 is also expressed in other midbrain cell types (La Manno et al., 2016; Arenas, 2020), such as endothelial and pericyte cells, ependymal cells and microglia, therefore, there is an intriguing question whether these cells can also been converted into dopaminergic neurons by PTB depletion in animal models of PD.