While most HTT protein interactions that are disease modifiers have been defined in HD model organisms, there are several interactions identified as human genetic HD modifiers from genome-wide association studies, including TCERG1 (Holbert et al, 2001; Kaltenbach et al, 2007; Andresen et al, 2007; Lobanov et al, 2022), MSH3 (Shirasaki et al, 2012; Flower et al, 2019), and more recently MLH1-PMS2 (Lee et al, 2017; Sun et al, 2024) and POLD1 (Ripaud et al, 2014; Consortium et al, 2024). The gene discussed is MLH1; the disease is Huntington disease.