Investigating the role of dysregulated neuronal protein synthesis in a Tuberous Sclerosis model

• Applicant: Dr. Kristina Jülich
• Subject Area: Pediatric and Adolescent Medicine ; Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2011 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 208260042

Tuberous Sclerosis Complex (TSC) is a genetic disorder characterized by growth of benign tumors in multiple organs. The etiology of the accompanying neurological symptoms, such as cognitive and behavioral abnormalities or seizures remains unclear since TSC patients can show symptoms in the absence of gross structural brain abnormalities. Recent work has suggested aberrant axonal connectivity to contribute to the neurological phenotype.TSC is caused by mutations of either the TSC1 or the TSC2 gene, which function as inhibitors of cell growth and protein synthesis in normal cells. Inactivation of either one by mutation or phosphorylation results in activation of the mTORC1 pathway and enhanced protein translation via its substrates S6K1 and 4E-BP1. In addition, there is growing evidence for mTORC1 involvement in axonal guidance and regeneration. The effect on protein synthesis is specific rather than general, since total neuronal protein levels remain unchanged in TSC-deficient cells, and SAD-A kinase protein, but not mRNA levels are regulated in an mTORC1-dependent manner. We hypothesize that dysregulated mRNA translation through activation of the mTORC1 pathway contributes to the misguided neuronal connections in TSC, and therefore propose to analyze translational profiles of TSC-deficient neurons upon changes of mTORC1/S6K1 pathway signaling. In contrast to conventional transcriptional profiling, this approach allows comparison of only actively translating mRNAs in specific cell types. Specifically, I will use the TRAP approach (Translating Ribosome Affinity Purification) in Tsc2-knockdown neurons to identify actively translating mRNAs. I will compare the translation profiles after inhibition of mTORC1 or its substrate S6K1, verify the results on protein level and finally characterize the effect of the candidates on axon morphology.The long-term goal of my project is to identify novel potential targets for therapeutic intervention in individuals with TSC.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Mustafa Sahin