Posted November 13, 2015
Note: Bolded hyperlinks will direct you to the investigators' public and technical abstracts, and publications, if applicable.
Dr. David Gutmann (FY02; Washington University in St. Louis) generated mice models with TSC1-deficient neuroglial cells (brain cells important for nerve and support cell formation) and investigated the critical cellular and genetic parameters that culminate in seizures. His data showed that neuroglial cells deficient in TSC1 expression differentially expressed proteins involved in cell adhesion and cell-cell interactions, including the protein adhesion molecule on glia (AMOG). He was also able to show that AMOG activates the mTOR pathway independent of TSC and Rheb.
Dr. Scott Baraban (FY05; University of California, San Francisco) developed a zebrafish model for TSC to test the hypothesis that loss of TSC gene function directly impacts neuronal/synaptic function resulting in hyperexcitability and seizures. Using this animal model, he found that reduced expression of Tsc1 can lead to seizure-like behavior and electrographic seizure activity. Interestingly, the seizure-like behavior was not ameliorated by rapamycin. Results from these studies were also published in a chapter of the book, Animal Models of Epilepsy: Methods and Innovations.
Dr. Angelique Bordey (FY09; Yale University) generated the first TSC animal model that replicates the discrete cortical tubers seen in humans using a then-novel approach combining in utero electroporation in inducible transgenic mice. Using this mouse model, she identified some of the mechanisms of lesion formation, provided insights regarding the state of astrocyte activation in and surrounding cortical lesions, and identified cortical circuit abnormalities following Tsc1 removal in embryonic progenitor cells and neurons including hypertrophic dendritic arborization, ectopic neuronal location, and the presence of binucleated neurons. Moreover, she identified several proteins, such as hypoxia inducible factor 1 (Hif1a), that play an important role in the formation of lesions in TSC.
Dr. David Sulzer (FY11; Columbia University) created a GFAP-Cre-mediated Tsc1 conditional knockout mouse that develops spontaneous seizures at 2-3 months to explore the mechanism for epileptogenesis in TSC. With this mouse model and other techniques, he was able to show that TSC1 gene depletion results in astrocytic mTOR hyperactivation and reactive astrogliosis, a universal response of astrocytes to toxic and/or traumatic insults. Findings from this research show that although the deletion of the Tsc1 gene does not interfere with astrocyte glutamate uptake and potassium buffering, there is a slight decrease in astrocyte uptake of synaptically evoked glutamate after a clinical seizure. Astroglial TSC1 deletion led to increased basal and evoked excitatory synaptic transmission during epileptogenesis, as well as increased excitatory synapses prior to clinical seizures. When TSC is deleted directly from pyramidal neurons, greater intrinsic excitability is also observed, as is a higher response to excitatory input, both of which are likely to lead to the initiation and prolongation of epileptic activity.