CHRNA4 and Huntington disease: RVG29 (YTIWMPENPRPGTPCDIFTNSRGKRASNG), a rabies virus glycoprotein (RVG)-derived peptide containing 29 amino acids,186 is the most representative ligand peptide for nAchR.187–189 RVG29 modification enables nanoparticles to efficiently cross the BBB and recognize neurons, applying to various CNS disorders, such as major depressive disorder (MDD),190 Alzheimer’s disease (AD),191,192 PD,193,194 Huntington’s disease (HD)195 and cerebral ischemia (CI).196