HTT and Huntington disease: Focusing on these novel genes with no pre-existing links in the literature, the two methods both implicate the HTT gene, which is known to be the causative gene for the neurodegenerative disorder Huntington disease, MeSHOP comparison ranks the XRCC3 gene highly, a DNA repair gene that could be involved in apoptosis and neuronal cell death (both of which are mechanisms associated with AD in the literature).