HTT and juvenile Huntington disease: Huntington’s disease (HD) is an autosomal dominant, inherited neurodegenerative disease, which is mainly due to the excessive expansion of CAG trinucleotide repeats in the huntingtin gene in chromosome 4, leading to the abnormal of polyglutamine near the N-terminal of the HTT (Mizushima and Komatsu, 2011; Dayalu and Albin, 2015; Huang et al., 2018).