Neuronal Expression of Familial Parkinson's Disease A53T α-Synuclein Causes Early Motor Impairment, Reduced Anxiety and Potential Sleep Disturbances in Mice
Affiliations: Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, USA | Molecular Neuropsychiatry Research Branch, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, USA | Laboratory of Clinical Investigation, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, MD, USA
Note: [] Correspondence to: Sarah M. Rothman, PhD, Laboratory of Neurosciences, National Institute on Aging Intramural Research Program, National Institutes of Health, 251 Bayview Blvd, Baltimore, MD 21224, USA. Tel.: +1 908 740 7390; E-mail: srothman02@gmail.com
Abstract: Background: Mutations in the human α-synuclein gene lead to early-onset Parkinson's disease (PD); however, phenotypes of α-synuclein mutant mice vary depending upon the promoter driving transgene expression. Objective: The goal of this study was to characterize behavior and neurochemical alterations in mice expressing mutant (A53T) human α-synuclein, controlled by a neuron-specific Thy-1 promoter. Our data provide important additional phenotypic and biochemical characterization of a previously generated model of PD. Methods: A53T (SNCA) and wild type (WT) littermate mice were evaluated for motor function (rotarod and stride length) and anxiety (elevated plus maze and open field) every 2 weeks. At 24 weeks mice were evaluated in a Comprehensive Lab Animal Monitoring System (CLAMS). A separate cohort of mice were euthanized at 12, 24 and 36 weeks for immunoblot analysis of α-synuclein, dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the striatum, and hypothalamic serotonin and metabolites were measured. Results: SNCA mice display significant motor deficits at 14–18 weeks of age compared to WT mice, which progress over time. CLAMS analysis revealed an increase in activity during the dark phase and a reduction in overall estimated sleep time for SNCA mice compared to WT consistent with clinical reports of sleep abnormalities in PD. A transient change in the levels of DAT appeared at 12 weeks in the striatum and serotonin levels were also altered in the hypothalamus at this time point. Conclusions: This PD model displays consistent and clinically relevant motor and sleep phenotypes. Anxiety phenotypes are consistent with other α-synuclein based PD models yet incongruous with typical clinical symptoms. Early increases in serotonin levels potentially explain reductions in anxiety behaviors and sleep.
