CRISPR/Cas9- mediated precise genome editing represents one of the most promising approaches to clinical management of a variety of human genetic diseases in the central nervous system (CNS). However, translation of this technology for clinical applications has been limited by several major hurdles, including the lack of safe approaches for efficient, specific delivery of Cas9, sgRNA, and donor DNA simultaneously to the disease location, the limited homology-directed repair (HDR) frequency due to the predominant role of non- homologous end-joining (NHEJ) in DNA repair, and the inability to cross the blood-brain barrier (BBB). To overcome those challenges, we propose to develop novel, simple polymeric NPs that are optimized for delivery of precise genome editing to the brain through both locoregional and systemic administration. As preliminary work, we developed novel chemistry and synthesized a group of terpolymers for gene delivery. We established an array of techniques for locoregional delivery of nanoparticles (NPs) to the brain via convection-enhanced delivery (CED), as well as an effective approach for systemic delivery of NPs to the brain via autocatalytic brain- targeting (ABT). We synthesized grafted terpolymeric NPs that can mediate efficient delivery of genetic materials, including CRISPR/Cas9, to the brain. We discovered leucine-rich repeat-containing protein 31 (LRRC31) that preferentially inhibits NHEJ and significantly enhances the efficiency of CRISPR/Cas9- mediated precise genome editing. Building on those progress, we propose to synthesize grafted polymeric NPs that are optimized for CRISPR/Cas9 delivery, identify LRRC31 motifs responsible for NHEJ inhibition, and evaluate them for direct, locoregional delivery and systemic delivery of precise genome editing to the mouse brain in the UG3 Development Phase, and to develop approaches to scaling up the synthesis of polymers and NPs, and evaluate them in experimental pigs in the UH3 Demonstration Phase. Successful completion of the study will establish a versatile platform for efficient delivery of CRISPR/Cas9- mediated precise genome editing to the brain, which could be potentially translated into clinical applications.