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W. Ma, S.–Z. Wang; Sox2 Initiates RPE Transdifferentiation in vitro and Alters RPE Properties in vivo . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3126.
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© ARVO (1962-2015); The Authors (2016-present)
To study whether sox2, a gene encoding a HMG–box transcription factor known to be present in neural stem cells, induces RPE transdifferentiation toward neural retina.
The coding region of chick sox2 was PCR–amplified based on published information and inserted into proviral DNA of RCAS, a replication–competent retrovirus. To achieve misexpression of sox2 in the developing eye, RCAS–sox2 virus was microinjected into the subretinal space of day 2 chick embryos. Eyes receiving the virus were fixed at various developmental stages and analyzed for phonotypical alterations. The RCAS–sox2 virus was also used to infect cultured RPE cells to study whether sox2 was sufficient to induce de novo expression of properties typical of retinal neurons in the otherwise non–neural, RPE cell culture.
We first analyzed what cells of the developing retina expressed sox2. In situ hybridization showed that at early developmental stages, sox2 was expressed in progenitor cells distributed across the entire thickness of the retinal neuroepithelium. At later stages when the retinal has developed its stratification, expression of sox2 was restricted to glial cells, a small number of amacrine cells occupying discrete anatomical locations, and a small number of cells in the ganglion cell layer. Retroviral–driven misexpression of sox2 in embryonic eye caused de–pigmentation of the RPE. In RPE cell culture, sox2 induced transdifferentiation identified by de novo expression of retinal cell markers, including RA4, Ap2a, calretinin, neurofilament (160 kDa), a neurofilament–associated antigen recognized by 3A10, microtubule–associate proteins (MAP2), and vimentin. RT–PCR showed that sox2 inhibited the expression of RPE gene mitf.
sox2 is expressed in the developing retina. The spatial and temporal pattern of sox2 expression and the results from our gain–of–function analyses suggest that sox2 plays a role in establishing retina vs. RPE identity.
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