PhD Proposal Examination
Friday April 21st, 1:10 pm – Room CCT 2150, University of Toronto at Mississauga
Christine Nguyen (Stewart lab)
“The Characterization of the Electrophysiological Properties of Three-Dimensional Bioengineered Human Skeletal Muscle and Neuromuscular Junctions“
Two-dimensional (2D) in vitro models of human skeletal muscle lack the architecture and contractile properties of a native muscle fiber, limiting them from being used for in vitro neuromuscular junction (NMJ) experimentation. A new method for creating three-dimensional (3D) human skeletal muscle tissues from human primary myogenic progenitors has been reported. The bioengineered muscle tissues are contractile, mimic’s clinical responses to drugs, and possess the epilson acetylcholine receptor (AChR) unit expressed in mature NMJs. Central to the communication of neurons and cells is the synapse, where transmission occurs via electrical and chemical signals between the close apposition of the pre- and post-synaptic cell membrane. At the vertebrate NMJ, acetylcholine is released from the pre-synaptic nerve terminal where it binds to AChRs on the postsynaptic muscle fiber. The flow of cations into the postsynaptic muscle cell induces a change in the membrane voltage that activates the muscle. The characterization of electrical properties of the muscle cells at rest, and when excited is crucial to advancing our understanding of the bioengineered muscles functionality. This proposed thesis will characterize the electrical properties in vitro 3D skeletal muscle tissue, and use it as the foundation for studying synaptic transmission of skeletal muscle tissues co-cultured with human pluripotent stem cell (hPSC) derived motor neurons (MN). Duchenne’s muscular dystrophy (DMD) is a fatal muscle disorder involving the skeletal muscle system. Little is known regarding the functional properties of the NMJ in DMD patients due to difficulties of in vivo experiments, and the lack of in vitro models. A new in vitro system of the NMJ will allow for further analysis in studying the integrity of skeletal muscles with regards to neuromuscular activity. Electrophysiological analyses of the model NMJ will be studied in both normal muscle cells, as well as in mutant cells with DMD.
PhD Proposal Exam
Thursday April 6th, 10:10 am – Earth Sciences Centre, Rm. 3087
Samantha Lauby (McGowan lab)
“Thyroid Hormones and Tactile Stimulation in Early-Life: An Investigation of Mechanisms Mediating Later-Life Stress Responses“
The stress response must be flexible in order to respond to a varying environment. It is also evident that the quality of care received in early life can affect later life stress responses in a long-term manner. In rodent models in the laboratory, handling by an experimenter early in life appears to optimally prepare pups for moderately stressful testing conditions in adulthood. Tactile stimulation provided by the mother in early life also appears to program stress-related responses in later-life. The thyroid system has been proposed to constitute a mechanism signaling these early life events. To investigate their interaction, I will use a 2×2 study design, with supplemental tactile stimulation and manipulating ambient temperature during separation, during an early-life handling procedure in rats. I will then identify changes in thyroid hormone activity in circulating blood and brain tissue. In addition, I will examine behavioural, physiological, and transcriptional components of stress-related responses in these offspring. Finally, I will characterize mechanisms that underlie identified gene expression changes. I hypothesize that the effects of supplemental tactile stimulation depend on a drop in body temperature with a subsequent release of thyroid hormone. This research will elucidate biological mechanisms by which animals adapt to their environments and outcomes related to a match or mismatch between early-life programming and the later-life environment.
PhD Proposal Exam
Thursday January 19th, 11:10 am – Ramsay Wright Building, Rm. 432
Lida Langroudi (Mitchell lab)
“Evaluating the role of Myrf in early development“
Throughout development, the precise spatio-temporal regulation of transcription is achieved through stage specific transcription factors (TFs) in response to internal and external queues. Using embryonic stem cells (mESCs) as a model system to recapitulate early embryonic fate indicated a robust up regulation of Myelin Regulatory Factor (MYRF) upon pluripotency exit. MYRF is well known for transcriptional regulation of myelination genes in oligodendrocytes, allowing terminal differentiation and survival in the central nervous system. It has been determined that MYRF works cooperatively with SOX10 to activate myelination genes by targeting their regulatory sequences. Although MYRF has been reported embryonic lethal, the causality and time of death has not been determined. Among the pluripotency factors that maintain self-renewal of ESCs, SOX2 is an essential transcription factor in embryonic development and ectodermal lineage where aberrations have been linked to many developmental defects. Considering the expression and relative association of MYRF and SOX family, I hypothesize that MYRF plays an essential role in early embryonic development by working cooperatively with SOX2. My preliminary data indicate co-expression and localization of MYRF with SOX2 in ESCs and pre-implanted embryos. First of all, to explore the role of MYRF in early embryonic development, I propose a knockout approach to examine the time and cause of embryonic lethality. Secondly, to investigate the transcriptional regulatory role of MYRF in ESCs, I will seek nuclear complexes associated with MYRF with emphasis on SOX2. Finally, by gaining new insight to cooperative factors involved with MYRF, I will determine the relative association and function of theses novel interactors in embryonic development.
Ramsay Wright is a wheelchair accessible building.