HTT and Huntington disease: We also were able to obtain Hdh3xFlag140Q/3xFlag140Q homozygotes from heterozygous intercrosses, but future studies comparing both the behavior and neuropathology in Hdh140Q/140Q and Hdh3xFlag140Q/3xFlag140Q mice are needed to determine to what extent an N-terminal tag on mutant htt could affect HD mouse model phenotypes.