SUPT4H1 and juvenile Huntington disease: Interestingly, here, we found that the transcriptional regulator Spt4 appears not to impact the toxicity of the expanded CAG repeat in the ATXN2 transgene, although it has been shown to be important for transcription of pathogenic CAG-repeats in Huntington’s disease transgenes and the GGGGCC repeat of ALS/FTD (45,46,50).