Background: Mutations in the TSC1 or in the TSC2 gene cause tuberous sclerosis complex (TSC), a developmental disorder characterized by tumor susceptibility in multiple organs and frequent neurological manifestations, such as seizures, intellectual disability, and autism. There is currently no cure for TSC, although significant progress has been made in recent years in managing some of the clinical traits, particularly tumor growth and epilepsy. However, much remains to be done to relieve the burden of epilepsy and cognitive problems, such as intellectual disability and autism. In line with the mission of the Tuberous Sclerosis Complex Research Program, the goal of this research is to improve our understanding of the pathogenesis of TSC, focusing on the cellular and molecular mechanisms that lead to the development of neurological symptoms. We believe that this basic knowledge can be translated into better treatments, and can ultimately improve the lives of TSC patients.Objective/Hypotheses: We hypothesize that heterozygous mutations in the TSC2 gene disrupt the normal development and function of excitatory neurons without affecting their size. Homozygous loss-of-function mutations, on the other hand, not only profoundly alter their size and intrinsic development, but also disrupt cell-cell communication with other cell types. These non-cell-autonomous mechanisms exacerbate defects in synaptic function and cognition, and possibly contribute to the formation of cortical tubers and tumors in the TSC brain. The specific objective of this study is to define the cellular abnormalities of excitatory neurons that are deficient in TSC2 activity and to understand how they impact the development of other neuronal and glial subtypes in the cerebral cortex.Specific Aims: (1) In vivo characterization of heterozygous and homozygous NEX-Tsc2 mice. (2) In vitro analysis of neuronal abnormalities and neuro-glia interactions in NEX-Tsc2 cultures.Study Design: We will utilize NEX-Tsc2, a conditional Tsc2 knockout mouse line in which gene deletion occurs specifically in embryonic forebrain excitatory neurons, the most abundant cell type in the developing cerebral cortex. Our preliminary data indicate that homozygous mutants exhibit cell-intrinsic defects as well as astrogliosis, suggesting that Tsc2 mutant excitatory neurons produce unidentified signals that induce inflammatory responses. In this study, we will fully characterize the neurodevelopmental defects of heterozygous and homozygous NEX-Tsc2 mice, including cell autonomous abnormalities in neuronal migration and growth, as well as non-cell autonomous effects. In collaboration with Dr. Anne Anderson, we will also use video-EEG recordings to determine whether heterozygous and homozygous NEX-Tsc2 mice exhibit seizures or increased susceptibility to chemoconvulsants. Our culture studies revealed that heterozygous NEX-Tsc2 excitatory neurons exhibit subtle, but significant developmental defects. We will study these defects in detail, and we will also examine the interaction between Tsc2 mutant neurons and other cell types. Finally, we will use RNAseq to identify the downstream factors that mediate cell-autonomous as well as non-cell-autonomous defects. Based on these findings, in the future we will screen or test pharmacological compounds that may be effective in suppressing the cellular abnormalities and the neurological phenotype of NEX-Tsc2 mutant mice.Innovation: This project is technically innovative in that it will utilize novel Tsc2 mutant animal model and culture systems. It is also conceptually highly innovative in that it focuses on the poorly understood phenotype of heterozygous Tsc2 forebrain neurons, and the interaction between mutant excitatory neurons and other neuronal and non-neuronal cells in the developing brain.Impact: This work will lead to the development of targeted strategies to suppress neuron and glia abnormalities in TSC, advancing our understanding of the neuropathology of the disease and laying the foundation for better treatments of epilepsy and cognitive dysfunction in TSC patients.
|Effective start/end date||8/1/16 → 7/31/19|
- Congressionally Directed Medical Research Programs (CDMRP)