Induced pluripotent stem (iPS) cells generated from patients hold great promise for studying diseases that affect the central nervous system, as differentiation into the neuronal lineage creates a limitless supply of affected cells for disease study. Rett syndrome (RTT) is a neurodevelopmental autism spectrum disorder primarily caused by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. Due to the inaccessibility of patient neurons, most of what is known about underlying phenotypes has been described using mouse models. iPS cells provide a potential solution, but reprogramming of patient cells is hampered by low efficiency, and early methods of identifying iPS cells involve transgenic techniques that are not translatable to human patient samples. The first part of this thesis describes the generation and characterization of a pluripotency reporter to address this issue. The EOS lentiviral reporter allows real-time observation of pluripotency changes during reprogramming, and is a useful tool for more efficient isolation of reprogrammed cell lines. Further, the EOS selection system can be used in a disease context to reproducibly mark and maintain disease-specific iPS cell lines for future use in disease modelling. Though iPS cells have been used to study RTT in vitro, extensive assessments of neuron function and electrophysiology have not yet been performed. In the second part of this thesis, iPS cell lines generated from a RTT mouse model were tested for their ability to model disease in vitro. Directed differentiation of multiple Mecp2-deficient and wild-type iPS cell lines to glutamatergic neurons revealed neurons that lack Mecp2 have a smaller soma size, diminished sodium currents, and are less excitable, firing fewer, prolonged action potentials that are smaller in magnitude. This deficiency in intrinsic excitability was accompanied by a dysfunction at excitatory glutamatergic synapses, which together recapitulate changes previously observed in the Mecp2-deficient mouse brain. Having accumulated counts and recordings from hundreds of neurons with consistent responses among lines, the iPS cell system is a representative model of the neuronal and synaptic defects in RTT. These results illustrate the requirement of MeCP2 in normal neuronal function, and suggest altered neuronal homeostasis or aberrant network circuitry may underlie RTT pathogenesis.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/33992 |
| Date | 11 December 2012 |
| Creators | Farra, Natalie |
| Contributors | Ellis, James |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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