Parkinson disease is characterized by loss of dopamine neurons in the substantia nigra 1. Similar to other major neurodegenerative disorders, no disease-modifying treatment exists. While most treatment strategies aim to prevent neuronal loss or protect vulnerable neuronal circuits, a potential alternative is to replace lost neurons to reconstruct disrupted circuits 2. Herein we report an efficient single-step conversion of isolated mouse and human astrocytes into functional neurons by depleting the RNA binding protein PTB. Applying this approach to the mouse brain, we demonstrate progressive conversion of astrocytes into new neurons that can innervate into endogenous neural circuits. Astrocytes in different brain regions are found to convert into different neuronal subtypes. Using a chemically induced model of Parkinson’s disease, we show conversion of midbrain astrocytes into dopaminergic neurons whose axons reconstruct the nigro-striatal circuit. Significantly, re-innervation of striatum is accompanied by restoration of dopamine levels and rescue of motor deficits. Similar disease phenotype reversal is also accomplished by converting astrocytes to neurons using antisense oligonucleotides to transiently suppress PTB. These findings identify a potentially powerful and clinically feasible new approach to treating neurodegeneration by replacing lost neurons.