Base editing of Ptbp1 in neurons alleviates symptoms in a mouse model of Parkinsons disease

Parkinsons disease (PD) is a multifactorial disease caused by irreversible progressive loss of dopaminergic neurons (DANs). Recent studies reported successful conversion of astrocytes into DANs by repressing polypyrimidine tract binding protein 1 (PTBP1), which led to a rescue of motor symptoms in a chemically-induced mouse model of PD. However, several studies have challenged the validity of this cell type conversion since its publication. Here, we devised an adenine base editing strategy to downregulate PTBP1 in astrocytes and neurons in a chemically-induced PD mouse model. Using a combined approach of immunofluorescence and behavioral experiments, we found that PTBP1 downregulation in neurons, but not astrocytes, of the substantia nigra pars compacta and striatum resulted in the expression of tyrosine hydroxylase in non-dividing neurons and the rescue of forelimb akinesia and spontaneous rotations. Phenotypic analysis using multiplexed iterative imaging indicated that the majority of TH-positive cells in the striatum also expressed the dopaminergic marker DAT and pan-neuronal marker NEUN, further corroborating the dopaminergic and neuronal identity of these cells. Moreover, co-expression of TH, DAT, and NEUN was mostly identified in mature GABAergic neurons, including medium spiny neurons and interneurons. Further research is needed to decipher the functions of these cells as well as provide detailed mechanistic insights underlying the expression of the observed markers and rescue of spontaneous motor behaviors.