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

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

The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells-6

<p><b>Copyright information:</b></p><p>Taken from "The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells"</p><p>BMC Cancer 2004;4():44-44.</p><p>Published online 6 Aug 2004</p><p>PMCID:PMC512292.</p><p>Copyright © 2004 Martinez et al; licensee BioMed Central Ltd.</p>A was isolated on day 8 and analyzed by real-time RT-PCR. The columns and error bars represent the means and standard deviations of three independent experiments. B. Cell cycle distribution of siRNA-treated cells in the absence and presence of growth factors. Kasumi-1 cells were analyzed on day 8 by FACS analysis as described in Materials and Methods. C. Amount of S phase cells in dependence on the length of RUNX1-CBFA2T1 depletion. D. Amount of senescent cells dependence on the length of RUNX1-CBFA2T1 depletion. Growth factors are indicated below the graphs. The data shown in B, C and D were obtained from the same time course experiment. Cells were electroporated with the indicated siRNAs at days 0, 4, 8 and 12, and were analyzed on days 4, 8, 12 and 16

The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells-3

<p><b>Copyright information:</b></p><p>Taken from "The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells"</p><p>BMC Cancer 2004;4():44-44.</p><p>Published online 6 Aug 2004</p><p>PMCID:PMC512292.</p><p>Copyright © 2004 Martinez et al; licensee BioMed Central Ltd.</p>rmined at the indicated days using trypan blue counting. Arrows indicate electroporations. B. Graphical representation of cell doubling times. The columns represent the means of three independent experiments. Error bars indicate standard deviations. *, p < 0.05 according to Student's t-test. C. Graphical representation of the cell cycle phase distribution. Kasumi-1 cells were electroporated at days 0 and 4, and were examined at day 8 using FACS analysis. The columns and error bars represent the mean values and standard deviations of three independent experiments. †, p < 0.01 according to Student's t-test. C. RUNX1-CBFA2T1 suppression is associated with increased CDKN1B (p27) levels. After electroporation at days 0 and 4, total cell lysates were prepared at day 8 and analyzed using immunoblotting. After CDKN1B detection, the membrane was stripped and reprobed with an anti-tubulin antibody. The siRNAs are indicated on top. Arrows on the left mark RUNX1-CBFA2T1, RUNX1, CDKN1B (p27) and tubulin proteins. The relative ratios between CDKN1B and tubulin are indicated below the blot

The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells-0

<p><b>Copyright information:</b></p><p>Taken from "The oncogenic fusion protein RUNX1-CBFA2T1 supports proliferation and inhibits senescence in t(8;21)-positive leukaemic cells"</p><p>BMC Cancer 2004;4():44-44.</p><p>Published online 6 Aug 2004</p><p>PMCID:PMC512292.</p><p>Copyright © 2004 Martinez et al; licensee BioMed Central Ltd.</p> electroporation with 100 nM siRNAs and analyzed by immunoblotting. The electroporated cells and siRNAs are indicated on top. Arrows on the right mark RUNX1-CBFA2T1 and RUNX1 proteins. Markers are shown on the left, and the relative ratios between RUNX1-CBFA2T1 and RUNX1 are indicated below the blot. B. Time course of siRNA-mediated RUNX1-CBFA2T1 depletion. Kasumi-1 nuclear lysates were isolated at the indicated days after electroporation with 100 nM siRNA and analyzed by immunoblotting. Values were normalized to the control siRNA siAGF6

<i>Elk3</i> Deficiency Causes Transient Impairment in Post-Natal Retinal Vascular Development and Formation of Tortuous Arteries in Adult Murine Retinae

<div><p>Serum Response Factor (SRF) fulfills essential roles in post-natal retinal angiogenesis and adult neovascularization. These functions have been attributed to the recruitment by SRF of the cofactors Myocardin-Related Transcription Factors MRTF-A and -B, but not the Ternary Complex Factors (TCFs) Elk1 and Elk4. The role of the third TCF, Elk3, remained unknown. We generated a new <i>Elk3</i> knockout mouse line and showed that Elk3 had specific, non-redundant functions in the retinal vasculature. In <i>Elk3(−/−)</i> mice, post-natal retinal angiogenesis was transiently delayed until P8, after which it proceeded normally. Interestingly, tortuous arteries developed in <i>Elk3(−/−)</i> mice from the age of four weeks, and persisted into late adulthood. Tortuous vessels have been observed in human pathologies, e.g. in ROP and FEVR. These human disorders were linked to altered activities of vascular endothelial growth factor (VEGF) in the affected eyes. However, in <i>Elk3(−/−)</i> mice, we did not observe any changes in VEGF or several other potential confounding factors, including mural cell coverage and blood pressure. Instead, concurrent with the post-natal transient delay of radial outgrowth and the formation of adult tortuous arteries, Elk3-dependent effects on the expression of Angiopoietin/Tie-signalling components were observed. Moreover, <i>in vitro</i> microvessel sprouting and microtube formation from P10 and adult aortic ring explants were reduced. Collectively, these results indicate that Elk3 has distinct roles in maintaining retinal artery integrity. The <i>Elk3</i> knockout mouse is presented as a new animal model to study retinal artery tortuousity in mice and human patients.</p></div