Progressive gene dose-dependent disruption of the methamphetamine-sensitive circadian oscillator-driven rhythms in a knock-in mouse model of Huntington's disease
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Ouk, K., Aungier, J., & Morton, J. (2016). Progressive gene dose-dependent disruption of the methamphetamine-sensitive circadian oscillator-driven rhythms in a knock-in mouse model of Huntington's disease. Experimental Neurology, 286 69-82. https://doi.org/10.1016/j.expneurol.2016.09.007
Huntington's disease (HD) is a progressive genetic neurodegenerative disorder characterised by motor and cognitive deficits, as well as sleep and circadian abnormalities. In the R6/2 mouse, a fragment model of HD, rest-activity rhythms controlled by the suprachiasmatic nucleus disintegrate completely by 4 months of age. Rhythms driven by a second circadian oscillator, the methamphetamine-sensitive circadian oscillator (MASCO), are disrupted even earlier, and cannot be induced after 2 months of age. Here, we studied the effect of the HD mutation on the expression of MASCO-driven rhythms in a more slowly developing, genetically relevant mouse model of HD, the Q175 ‘knock-in’ mouse. We induced expression of MASCO output by administering low dose methamphetamine (0.005%) chronically via the drinking water. We measured locomotor activity in constant darkness in wild-type and Q175 mice at 2 (presymptomatic), 6 (early symptomatic), and 12 (symptomatic) months of age. At 2 months, all mice expressed MASCO-driven rhythms, regardless of genotype. At older ages, however, there was a progressive gene dose-dependent deficit in MASCO output in Q175 mice. At 6 months of age, these rhythms could be observed in only 45% of heterozygous and 15% of homozygous mice. By 1 year of age, 90% of homozygous mice had an impaired MASCO output. There was also an age-dependent disruption of MASCO output seen in wild-type mice. The fact that the progressive deficit in MASCO-driven rhythms in Q175 mice is HD gene dose-dependent suggests that, whatever its role in humans, abnormalities in MASCO output may contribute to the HD circadian phenotype.
transgenic mice, dopamine, sleep, preconditioning
This work was supported by a grant from CHDI Foundation, Inc. (USA).
External DOI: https://doi.org/10.1016/j.expneurol.2016.09.007
This record's URL: https://www.repository.cam.ac.uk/handle/1810/261069
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