Base editing of $Ptbp1$ in neurons alleviates symptoms in a mouse model for Parkinson’s disease

Parkinson’s disease (PD) is a multifactorial disease caused by irreversible progressive loss of dopaminergic neurons. Recent studies reported successful conversion of astrocytes into dopaminergic neurons by repressing polypyrimidine tract binding protein 1 (PTBP1), which led to a rescue of motor symptoms in a mouse model for PD. However, the mechanisms underlying this cell type conversion remain underexplored and controversial. Here, we devised a strategy using adenine base editing to effectively knockdown PTBP1 in astrocytes and neurons in a PD mouse model. Using AAV delivery vectors at a dose of 2×108 vg per animal, we found that Ptbp1 editing in neurons, but not astrocytes, of the substantia nigra pars compacta and striatum resulted in the formation of tyrosine hydroxylase (TH)+ cells and the rescue of forelimb akinesia and spontaneous rotations. Phenotypic analysis of TH+ cells indicates that they originated from non-dividing neurons and acquired dopaminergic neuronal markers upon PTBP1 downregulation. While further research is required to fully understand the origin, identity, and function of these newly generated TH+ cells, our study reveals that the downregulation of PTBP1 can reprogram neurons to mitigate symptoms in PD mice.