HTT and Huntington disease: At the molecular level, the pathogenesis of HD is driven by toxicity from the full-length amplified Huntington protein and N-terminal Huntington fragments that are susceptible to hydrolysis-related misfolding, with abnormal HTT intron splicing and the somatic amplification of HTT gene CAG repeats further exacerbating these issues (Tabrizi et al., 2022).