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R.M. Saltzmann, A.C. Cirino, J.R. Mathura; Frizzled–4 mRNA Is Expressed in Cultured Rat Müller Cells and Is Upregulated in Hypoxia. . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2976.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Recently, a mutation in the putative Wnt receptor, frizzled–4 (FZD4) has been established as a cause of an autosomal dominant familial exudative vitreoretinopathy (FEVR). FEVR is characterized by a failure of peripheral retinal vascularization with subsequent retinal exudation and neovascularization. Possibly, FZD4 is involved in the pathogenesis of other retinal diseases in which angiogenesis is a feature. This study was designed to determine whether FZD4 mRNA is expressed in cultured rat Müller cells and to test whether its expression is altered by hypoxia. Methods: A well–characterized rat Müller cell line, rMC–1, was used in these experiments. Total RNA was isolated from Müller cells exposed to either control or hypoxic conditions. RT–PCR was performed on RNA isolated from control and hypoxic samples using primers for rat FZD4 and 16S ribosomal RNA, the internal control. The resultant PCR products were run on agarose gels. The gels were analyzed and quantified using optical density measurement of the FZD4 band relative to 16S band. Results: Bands of appropriate size for FZD4 (462 bp) and 16S (197 bp) were found by PCR. DNA sequencing of the FZD4 band established that the PCR product was homologous to the published sequence for rat FZD4. Optical density analysis of the bands in three separate experiments demonstrated a 4.5 fold increase in FZD4 expression in the Müller cells grown in hypoxia when compared to normoxia. Conclusions: FZD4 is expressed in rMC1 cells and its mRNA is markedly increased in rMC1 cells exposed to hypoxia. This raises the possibility that alterations in FZD4 levels in Müller cells play a role in the retina's response to hypoxia. Therefore, FZD4 may be important in the pathogenesis and treatment of ischemic retinopathies.
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