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L. A. Wiley, L. K. Dattilo, M. Giovannini, D. C. Beebe; The Pathways Responsible for Defects in Nf2 Mutant Lenses. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2636.
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Patients with Neurofibromatosis Type 2 (NF2) develop glial tumors and posterior subcapsular cataracts (PSCs). Nf2 encodes merlin, a member of the Band 4.1 superfamily, which often link the actin cytoskeleton to the plasma membrane. Merlin also inhibits multiple intracellular signaling pathways. We found that Nf2 is required for cell cycle exit, fiber cell differentiation, apical-basal polarity and separation of the lens vesicle from the surface ectoderm. Studies were designed to determine whether these phenotypes were primarily due to aberrant cytoskeletal function or excess signaling.
Homozygous Nf2 flox (Nf2fx/fx); LeCre (+/-) mice were bred to delete Nf2 in the lens. Activation or suppression of signaling pathways was assessed using phospho(p)-specific antibodies and confocal immunofluorescence microscopy. Pregnant dams were injected with the inhibitors U0126, PP2 or rapamycin beginning on E9.5. Control litters received solvent only (DMSO). Embryos were collected on E11.5 and phenotypic rescue was assessed by labeling with the thymidine analog EdU (proliferation), antibodies to FoxE3 (differentiation) and ZO-1 (polarity) and morphology (vesicle separation).
Initial data suggests that the MEK-ERK activation is not necessary for lens development between E9.5 and E11.5 and that hyperactivation of the MEK-ERK pathway does not contribute to the abnormalities seen in Nf2CKO lenses. Other signaling pathways may be involved, or disruption of cytoskeleton-membrane interaction may be the primary cause of the mutant phenotype. Rescue of any of the Nf2CKO phenotypes could lead to insight about why PSCs form and tumors develop in NF2 patients.
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