Taking Huntington’s disease as an example, the mutant HTT gene encodes the toxic and aggregation-prone mutant huntingtin (mHTT) protein with an expanded polyQ tract translated from the expanded CAG repeats, and the accumulation of the mHTT protein will lead to neuronal cell death due to altered neural circuitry, mitochondrial dysfunction, transcriptional dysregulation, disrupted protein homeostasis, impaired protein degradation, and aberrant activation of stress responses [6,7,8,9,10]. This evidence concerns the gene HTT and juvenile Huntington disease.