Neurofibromatosis type 2 (NF2) is a dominantly inherited genetic disorder predisposing to the development of nervous system tumors such as bilateral vestibular schwannomas, cranial and spinal meningiomas, nerve root schwannomas and ependymomas. The majority of NF2 patients develop juvenile lens opacities often presenting prior to the development of tumors usually in early teens. The NF2 gene had been identified by positional cloning. It encodes a recessive tumor suppressor protein mutated in both sporadic and familial schwannomas and meningiomas. We have isolated the mouse homologue of the NF2 gene (Nf2) from an 18-day old mouse brain cDNA library. Nf2 encodes a 596 amino acid-protein, schwannomin (alternatively merlin), with 98% identity to the human NF2 protein. By characterizing a dinucleotide repeat polymorphism within the 3$ sp prime$ untranslated region of Nf2, we have mapped the mouse gene to the proximal end of chromosome 11 at a small region of conserved synteny to human chromosome 22. These results indicate that Nf2 is highly conserved and suggest that analysis of the mouse Nf2 gene might yield insights into the human gene. / Schwannomin shares homology with members of erythrocyte band 4.1 superfamily which are known to be localized in the membrane-cytoskeleton interface. The predicted secondary structure of schwannomin includes an amino-terminal domain which is highly conserved within the superfamily and is proposed to associate with plasma membrane proteins, and a carboxy-terminal domain of lower homology but hypothesized to associate with the cytoskeleton. By Northern and Western analyses, Nf2 is expressed in all tissues studied. However, analysis by RNA in situ hybridization and immunohistochemistry revealed a widespread but cell-type specific pattern of expression. Furthermore, immunofluorescence technique showed cytoplasmic localization in neuronal and non-neuronal cells. When analysed in lens and Schwann cells, two cell types affected by the NF2 phenotype, schwannomin localized to dynamic structures such as the ruffling membrane and leading edges. Fractionation of cellular proteins revealed the presence of schwannomin in the detergent-insoluble cytoskeletal fraction as an $ sim$80 kDa protein, consistent with the hypothesis that it functions in association with cytoskeleton proteins. Moreover, schwannomin's expression pattern in the lens indicated that it plays a role in differentiation-specific events. With these observations together with information on related proteins, we propose a working model that defines the role of schwannomin as a membrane organizing protein in the leading edge.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.42005 |
| Date | January 1996 |
| Creators | Claudio, Jaime O. |
| Contributors | Rouleau, Guy A. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001549492, proquestno: NQ29912, Theses scanned by UMI/ProQuest. |
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