Ataxin-1 is a protein with polyglutamine stretches that causes SCA1 through a toxic gain-of-function that involves nuclear aggregation of ATXN1 protein, and it has been described as the inter-cellular propagation of polyglutamine-expanded ATXN1 inclusions.33 Inter-cellular propagation of aggregated protein inclusions along actin-based tunnelling nanotubes has been reported as a mean of pathogenic spread in Alzheimer’s, Parkinson’s and Huntington’s diseases.34 Thus, we hypothesize that ataxin-1 could trigger the seeding propagation of other molecules such as a-syn. This evidence concerns the gene ATXN1 and juvenile Huntington disease.