Huntington's disease (HD) is one of the few neurodegenerative diseases with a known genetic cause, knowledge that has enabled the creation of animal models using genetic manipulations that aim to recapitulate HD pathology. The study of behavioral and neuropathological phenotypes of these HD models, however, has been plagued by inconsistent results across laboratories stemming from the lack of standardized husbandry and testing conditions, in addition to the intrinsic differences between the models. We have compared different HD models using standardized conditions to identify the most robust phenotypic differences, best suited for preclinical therapeutic efficacy studies. With a battery of tests of sensory-motor function, such as the open field and prepulse inhibition tests, we replicate previous results showing a strong and progressive behavioral deficit in the R6/2 line with an average of 129 CAG repeats in a mixed CBA/J and C57BL/6J background. We present the first behavioral characterization of a new model, an R6/2 line with an average of 248 CAG repeats in a pure C57BL/6J background, which also showed a progressive and robust phenotype. The BACHD in a FVB/N background showed robust and progressive behavioral phenotype, while the YAC128 full-length model on either an FVB/N or a C57BL/6J background generally showed milder deficits. Finally, the Hdh Q111 knock-in mouse on a CD1 background showed very mild deficits. This first extensive standardized cross-characterization of several HD animal models under standardized conditions highlights several behavioral outcomes, such as hypoactivity, amenable to standardized preclinical therapeutic drug screening.

Previous studies of the effects of coenzyme Q10 and minocycline on mouse models of Huntington's disease have produced conflicting results regarding their efficacy in behavioral tests. Using our recently published best practices for husbandry and testing for mouse models of Huntington's disease, we report that neither coenzyme Q10 nor minocycline had significant beneficial effects on measures of motor function, general health (open field, rotarod, grip strength, rearing-climbing, body weight and survival) in the R6/2 mouse model. The higher doses of minocycline, on the contrary, reduced survival. We were thus unable to confirm the previously reported benefits for these two drugs, and we discuss potential reasons for these discrepancies, such as the effects of husbandry and nutrition.

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