Endothelial SRF/MRTF ablation causes vascular disease phenotypes in murine retinae
Christine Weinl, … , Ralf H. Adams, Alfred Nordheim
Christine Weinl, … , Ralf H. Adams, Alfred Nordheim
Published April 8, 2013
Citation Information: J Clin Invest. 2013;123(5):2193-2206. https://doi.org/10.1172/JCI64201.
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Research Article Vascular biology

Endothelial SRF/MRTF ablation causes vascular disease phenotypes in murine retinae

Abstract

Retinal vessel homeostasis ensures normal ocular functions. Consequently, retinal hypovascularization and neovascularization, causing a lack and an excess of vessels, respectively, are hallmarks of human retinal pathology. We provide evidence that EC-specific genetic ablation of either the transcription factor SRF or its cofactors MRTF-A and MRTF-B, but not the SRF cofactors ELK1 or ELK4, cause retinal hypovascularization in the postnatal mouse eye. Inducible, EC-specific deficiency of SRF or MRTF-A/MRTF-B during postnatal angiogenesis impaired endothelial tip cell filopodia protrusion, resulting in incomplete formation of the retinal primary vascular plexus, absence of the deep plexi, and persistence of hyaloid vessels. All of these features are typical of human hypovascularization-related vitreoretinopathies, such as familial exudative vitreoretinopathies including Norrie disease. In contrast, conditional EC deletion of Srf in adult murine vessels elicited intraretinal neovascularization that was reminiscent of the age-related human pathologies retinal angiomatous proliferation and macular telangiectasia. These results indicate that angiogenic homeostasis is ensured by differential stage-specific functions of SRF target gene products in the developing versus the mature retinal vasculature and suggest that the actin-directed MRTF-SRF signaling axis could serve as a therapeutic target in the treatment of human vascular retinal diseases.

Authors

Christine Weinl, Heidemarie Riehle, Dongjeong Park, Christine Stritt, Susanne Beck, Gesine Huber, Hartwig Wolburg, Eric N. Olson, Mathias W. Seeliger, Ralf H. Adams, Alfred Nordheim

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Figure 7

NV causes non–uniformly distributed focal lesions in adult SRF-depleted retinae and results in retinal mislayering and photoreceptor degeneration.

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NV causes non–uniformly distributed focal lesions in adult SRF-depleted ...
(A) H&E staining on paraffin sections of SrfiECKO eyes showed retinal abnormalities, including NV lesion connecting to and rupturing the RPE (arrow), local displacement of ONL cells (double arrow), and mislayering of INL and ONL and thinning of the ONL (triple arrow), accompanied by local disruption of photoreceptors. (B) Semiquantitative RT-PCR analysis of Vegfa, Opn1, and Rho mRNA expression of whole retinal tissue of 6- to 8-month-old control and SrfiECKO animals. mRNA levels were normalized to Gapdh and expressed as percent of control. n = 6 per group. (C) Representative Western blot analysis of SRF levels in immortalized mECs transfected with control siRNA and siRNA against Srf for 2 or 3 days. GAPDH was used as a loading control. (D) Quantitation of Western blot analysis in C, normalized to GAPDH and expressed as percent of control siRNA. n = 5. (E) Semiquantitative RT-PCR analysis of Srf, Thbs1, Actb, and Cfl1 mRNA expression in immortalized mECs after transfection with siRNA against Srf compared with transfection with control siRNA. mRNA levels were normalized to Gapdh and expressed as percent of control. n = 5 experiments. (F) Quantitation of anti-SRF ChIP signals for promoter regions of Pak1 (CArG-box negative locus used as normalization control), Actb (positive reference), and Thbs1. n = 5. Scale bar: 50 μm (A). *P < 0.05, **P < 0.01, ***P < 0.001 vs. respective control.