Functional assessment of the RAS/MAPK pathway
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Rasopathies are a heterogeneous group of disorders that are due to dominant, gain-of-function mutations in genes in the RAS/MAPK pathway. The RAS/MAPK pathway is involved in regulating cell growth, differentiation, and apoptosis. There is marked clinical variation in clinical phenotypes among different rasopathies despite activation of the RAS/MAPK pathway, suggesting that there may be additional biochemical variables depending on the gene mutated. In this thesis, the activation of the end effectors of the RAS/MAPK pathway, MAPK and MEK, were analyzed using Western blots and flow cytometry in NF1, RIT1, and PTPN11 mutated fibroblasts and lymphoblasts. Although the mutated cell lines were expected to have higher levels of activation due to upregulation of the RAS/MAPK pathway, they were found to have decreased activation compared to the control cells. A suggested reason for these results is that negative feedback loops may decrease the level of activation in the pathway by having activated P-MAPK and P-MEK inhibit previous proteins in the pathway.