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I. Ahmad, A. V. Das, K. B. Mallya; Regulation of Retinal Stem Cells/Progenitors by Chromatin Remodeling ATPase, Brm. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4082.
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© ARVO (1962-2015); The Authors (2016-present)
Evidence suggests that different cell types in vertebrate retina are generated by retinal stem cells/progenitors in response to interactions between cell-intrinsic and cell-extrinsic factors. However, the role of developmental chromatin remodeling, an essential intrinsic mechanism for facilitating/inhibiting differentiation-specific gene expression, in the regulation of retinal stem cells/progenitors, remains little understood. Here, we demonstrate the role of Brm, an ATPase in SWI/SNF chromatin remodeling complex, in the regulation of early retinal stem cells/progenitors differentiation into RGCs.
E14 rat retinal stem cell/progenitors, enriched in neurospheres, were transduced with Brm retrovirus (Brm-pBabe) or treated with Brm siRNAs to perturb Brm expression, followed by examination of cell proliferation and RGC differentiation. The influence of chromatin remodeling function of Brm was examined by retrovirus-mediated transduction of dominant negative Brm (dnBRM-pBabe) in neurospheres. Reporter activites, driven by Brn3b/Shh/Hes1 promoters, were evaluated in response to perturbation of Brm expression and function to get an insight into Brm-mediated facilitation of differentiation.
The expression of Brm is developmentally regulated; Brm transcript levels increase during retinal histogenesis, suggesting their association with the process of differentiation. This notion is confirmed by a significant decrease in the proportion of RGCs in neurospheres in response to attenuation in Brm expression (siRNA-mediated) or function (dnBrm-mediated). Conversely, forced expression of Brm promoted RGC differentiation. Promoter-reporter assays, in response to perturbation of Brm expression and function, demonstrated that Brm facilitated and attenuated expression of Brn3b/Shh and hes1, respectively. ChIP analyses revealed association of Brm with Wt1/Brn3b on Brn3b/Shh promoter and with CSL on Hes1 promoter, suggesting its gene-specific recruitment.
Brm facilitates the differentiation of retinal stem cells/progenitors into RGCs by promoting expression and function of Brn3b and attenuating Notch signaling. Supported by Nebraska Tobacco Settlement and Biomedical Research and Research to Prevent Blindness. NONE
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