Research Divisions: Brain Research and Integrated Neurophysiology
Research Interests: Investigating how epigenetic factors influence neuronal function.
Keywords: Epigenetics, Rett Syndrome, Methyl DNA-Binding Factors, Behavior, Neurodegeneration.
We are interested in determining how epigenetic factors regulate the development, the maturation, and the overall function of the central nervous system. The importance of epigenetics to these events has been under-appreciated, but the discovery that the pediatric neurological disorder Rett syndrome is caused by mutations of the epigenetic factor MeCP2 has highlighted the importance of this system in brain development. The following are three investigative themes ongoing in our group.
Correcting the Rett Phenotype. Rett syndrome is a disorder in which synaptic development stalls. One key issue is whether this condition is irremediable, or could be corrected by the restoration of MeCP2 function to the mutant neurons. We have generated a transgenic mouse in which MeCP2 can be conditionally induced within the brain, and will use this mouse to test whether the reintroduction of normal MeCP2 improves the Rett-like condition of the mutant mice. If successful, this would provide proof of principle that Rett syndrome is amenable to gene therapy treatment. In related studies, we have shown that synaptic plasticity is impaired in the MeCP2-deficient hippocampus, and that this impairment correlates with diminished expression levels of the NR2A subunit of the NMDA receptor. This subunit is critical for synaptic maturation, and for the genesis of hippocampal synaptic plasticity. Using a series of pharmacological and NR2A reintroduction strategies, we will determine whether enhancing NR2A function improves synaptic maturation, synaptic plasticity, and/or the impaired behavior of MeCP2-deficient mouse.Epigenetics and Mental Retardation. By coincidence, our transgenic mice turn out to be an animal model for a recently described mental retardation syndrome boys that results from a duplication of the MeCP2 gene. Little is known about how the over-representation of MeCP2 affects neuronal function. Using our transgenic line, we will identify molecular changes contributing to this novel condition, and then attempt to develop strategies to correct the phenotype.Epigeneticss and Neurodegeneration. Inhibiting of histone deacetylases protects neurons from several forms of insult-induced degeneration. The critical complexes at which these agents act remain unknown. We believe methyl DNA-binding factor-associated histone deacetylases are involved, and have determined that neurons lacking a specific methyl DNA binding factor are less sensitive to some insults. We are now identifying the mechanism for the diminished sensitivity, determining whether the brain of a mouse lacking this factor is less sensitive in vivo. If successful, we will then attempt to develop an intervention strategy with clinical applicability.
Cell and tissue culture: Hippocampal cells, neurons.
Procedures: Adenovirus, behavioral tests, EEG, gene expression analysis, immunohistochemistry, immunocytochemistry, in-vivo electrophysiology, in-vivo recording of local field potentials, qRT-PCR, RT-PCR, siRNA, stereotaxic brain surgery, western blot.
Amplifier, analytical balances, benchtop centrifuge, blotting apparatus, confocal microscope, culture hood, culture incubators, cryostat, deconvolution fluorescence microscope, digital microscope, dissecting microscope, electrophysiology rig, fluorescence microscope, gel apparatus, low- and high-speed centrifuge, low and ultralow freezers, plate reader, pneumatic picopump, ProBlot hybridization oven, real-time/thermocycler, stirrer/hot plate, vibratome, water baths.
Within the Department of Physiology:
Outside the Department of Physiology:
Liang Zhang, Neuroscience, Toronto Western
Joanne Nash, UT Scarborough
Alan Kozikowski, University of Illinois, Chicago
Lucas Pozzo-Miller, University of Alabama, Birmingham
Ellis James, Hospital for Sick Children, Toronto
Committee member/officer of national/international scientific organizations
Ontario Rett Syndrome Association (Scientific Advisory Panel Member)
University of Toronto Epilepsy Research Program (Advisory Board Member)
International Rett Syndrome Foundation (Scientific Advisory Board Member)