Neurofibromatosis type 1 (NF1) is a familial genetic disease of the nervous system. Individuals with NF1 are at risk for developing malignant peripheral nerve sheath tumors (MPNSTs), a cancer of the connective tissue surrounding the nerves and astrocytoma/glioblastoma (GBM) (Sorensen, Mulvihill and Nielsen 1986, Blatt et al. 1986), a devastating cancer in the brain. Studies have shown that modifier genes act in the disease NF1 to vary the phenotypic symptoms of the disease (Easton et al. 1993). In the studies outlined in this dissertation, I explored the role of modifier genes acting in MPNSTs and astrocytoma/GBM in a mouse model of NF1. This mouse model has the Nf1 and Trp53 genes mutated on chromosome 11 (NPcis), and previous studies have shown that the incidence of the MPNSTs and astrocytoma/GBM varies with the parental inheritance of the mutant chromosome 11 (Reilly et al. 2006). I focused my studies more specifically on Grb10, using microarray analysis to identity this gene as differentially expressed in MPNSTs when the mutant chromosome 11 comes from the mother (NPcis maternal) versus the father (NPcis paternal). Grb10 is an imprinted signaling adaptor protein on chromosome 11 (Arnaud et al. 2003). I identified Grb10 as more highly expressed in NPcis maternal MPNSTs and demonstrated that Grb10 gene copy number is increased in NPcis maternal MPNST cell lines. I find that this increase in Grb10 gene copy number may be caused by NPcis maternal MPNST cell lines retaining the Grb10 portion of chromosome 11 when loss of heterozygosity (LOH) of wild type (WT) Nf1 and Trp53 occurs as there is an increase in fragmented chromosome 11's in these lines. I also suggest a possible role for Zrsr1, another gene differentially expressed in the NPcis MPNST exon microarrays, as a driving factor for the NPcis maternal MPNST cell lines to retain the fragmented portion of chromosome 11 with Grb10. I examined the imprinting of Grb10 in the NPcis MPNSTs, and I found expression of both maternal and paternal isoforms of Grb10. Because Grb10 has been shown to be only maternally expressed in the periphery of the mouse, this suggests loss of imprinting (LOI) which may also contribute to the increase in total Grb10 expression in NPcis maternal MPNSTs. Although the role of Grb10 in vitro remains unclear, NPcis;Grb10 mutant mice were generated to look at the role of Grb10 in vivo. Maternal mutation of Grb10 in cis to the NPcis mutations led to a significant increase in MPNST incidence and a significant decrease in survival. I examined GRB10 in human MPNST cell lines and found varying proliferation effects in vitro between lines when I decreased GRB10 levels. However, microarray data suggests GRB10 may be negatively correlated with proliferation in human MPNSTs. In all, these studies indicate possible mechanisms for the overexpression of Grb10 in NPcis maternal MPNSTs and identify Grb10 as a candidate modifier of NPcis MPNSTs.
|Advisor:||Reilly, Karlyne M., Lee, Norman H.|
|Commitee:||Ceryak, Susan M., Leitenberg, David, Patierno, Steven, Rood, Brian R.|
|School:||The George Washington University|
|School Location:||United States -- District of Columbia|
|Source:||DAI-B 73/07(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Genetics|
|Keywords:||Grb10, MPNSTs, Neurofibromatosis, Nf1|
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