Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder associated with an inherited germline mutation in the NF1 tumor suppressor gene. With an incidence rate of 1 in 3500 individuals, the disease is characterized by changes in skin pigmentation and peri-nuclear tumor manifestation under the skin, which may lead to multiple benign and malignant tumor development along the nerves. The disease is also associated with memory disorders, often attributed to abnormalities in the N-methyl-D-aspartate receptor-associated Ras-GTP pathway and atypical neurofibromin protein expression. Although, the interaction of the neurofibromin protein with the NMDAR (GluN2B) is well documented, the role of the protein in the modulation of NMDAR-mediated Ras-GTP and long-term potentiation (LTP) is poorly understood. Here, we use mouse embryonic stem cell- derived neurons with wild type/homozygous and heterozygous neurofibromin gene expression [Nf1(+/+), Nf1(+/-) and Nf1(-/-) neurons] as a model to investigate the transcription/translational impact of GluN2B agonist/antagonist on Ras-GTP pathway associated molecules. We show that the in the regulation of the Ras-MAPK pathway and induction of synaptic strength is tightly regulated by neurofibromin in the Nf1(+/+) neurons. However, in the neurons [Nf1(+/-) and Nf1(-/-)] with an abnormal neurofibromin protein activity, Ras-GTP modulation and neuronal excitability can be achieved by GluN2B receptor modulation. Furthermore, observed that in Nf1 (+/-) and Nf1 (-/-) neurons with abnormal neurofibromin-Ras-GAP activity, ERK-c-FOS could compensate for neuronal activity and strength regulation.
We also quantified the synaptic redistribution of the GluN2B subunit in the Nf1 (+/+) and Nf1 (+/-) neurons before and after agonist/antagonist induction (drug bath). The percentage of the synaptic localization of the GluN1/2B receptors with Synapsin-1 in the axons was calculated. Our data also suggested a decrease in the neurofibromin protein in the neurons having a direct impact on the synaptic GluN2B dynamics and their implication on the Ras-MAPK pathway. Additionally, transfection of Nf1 (+/-) neurons with the NF1 gene was performed to restore the control of Ras-GTP activity in the Nf1(+/-) neurons.
|Advisor:||Coleman, Natalia, Murphy, Suzanne K.|
|Commitee:||Heindl, Jason E., Li, Zhiyu|
|School:||University of the Sciences in Philadelphia|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 79/04(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Neurosciences|
|Keywords:||GluN2B, N-methyl-D-aspartate receptors, NMDARs, Neurofibromin 1, Nf1, Ras-GTP|
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