miRNAs are involved in the pathogenesis of DR through the modulation of multiple pathogenetic pathways and may be novel therapeutic targets for the treatment of DR.
The microRNA-183/96/182 cluster is highly expressed in the retina and other sensory organs. To uncover its in vivo functions in the retina, we generated a knockout mouse model, designated "miR-183CGT/GT ," using a gene-trap embryonic stem cell clone. We provide evidence that inactivation of the cluster results in early-onset and progressive synaptic defects of the photoreceptors, leading to abnormalities of scotopic and photopic electroretinograms with decreased b-wave amplitude as the primary defect and progressive retinal degeneration. In addition, inactivation of the miR-183/96/ 182 cluster resulted in global changes in retinal gene expression, with enrichment of genes important for synaptogenesis, synaptic transmission, photoreceptor morphogenesis, and phototransduction, suggesting that the miR-183/96/182 cluster plays important roles in postnatal functional differentiation and synaptic connectivity of photoreceptors. M icroRNAs (miRNAs) are small, endogenous, noncoding, regulatory RNAs and represent a newly recognized level of gene-expression regulation (1-4). miRNAs have unique expression profiles in the developing and adult retina and are involved in normal development and functions of the retina in all species studied so far (5-12). miRNAs are dysregulated in the retina of retinal degenerative mouse models, suggesting their potential involvement in retinal degeneration (13,14). Conditional inactivation of dicer, an RNase III endonuclease required for miRNA maturation in cytosol (15), in the mouse retina resulted in alteration of retinal differentiation and optic-cup patterning, increased cell death, and disorganization of axons of retinal ganglion cells (16)(17)(18)(19), suggesting that miRNAs are important for normal development and functions of the mammalian retina. However, in vivo functions of individual miRNAs in the retina still are largely unknown.Previously, we identified a highly conserved, intergenic, sensory organ-specific, paralogous miRNA cluster, the miR-183/96/182 cluster (hereafter, miR-183/96/182), contained within an ∼4-kb genomic segment on mouse chr6qA3.3 (8, 9). In the adult retina, miR-183/96/182 is expressed specifically in all photoreceptors and in the inner nuclear layer (8, 10). Developmentally, its expression is minimal in the embryonic retina but increases dramatically after birth and peaks in the adult retina, suggesting a role for miR-183/ 96/182 in maturation and normal functioning of the adult retina (8, 9). Additionally, expression of miR-183/96/182 has a diurnal pattern, suggesting a potential role in rhythmic functions of the retina (8, 9). Recently, miR-183/96/182 also was shown to be light responsive, independent of the circadian cycle (20). Targeted deletion of miR-182 alone in mouse did not result in a discernible phenotype, suggesting functional compensation by miR-183 and miR-96 (21). Point mutations of miR-96 were reported to result in progressive, nonsyndromic hearing loss in both human (22) and mouse (23); however, there was no apparent retinal phenotype, an ob...
Rationale Vascular endothelial (VE)-cadherin localized at adherens junctions (AJs) regulates endothelial barrier function. As WNT (wingless) signaling-induced activation of the transcription factor Krüppel-like factor-4 (KLF4) may have an important role in mediating the expression of VE-cadherin and AJ integrity, we studied the function of KLF4 in regulating VE-cadherin expression and the control of endothelial barrier function. Objective The goal of this study was to determine the transcriptional role of KLF4 in regulating VE-cadherin expression and endothelial barrier function. Methods and Results Expression analysis, microscopy, chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assays (EMSA), and VE-cadherin-luciferase reporter experiments demonstrated that KLF4 interacted with specific domains of VE-cadherin promoter and regulated the expression of VE-cadherin at AJs. KLF4 knockdown disrupted the endothelial barrier, indicating that KLF4 is required for normal barrier function. In vivo studies in mice showed augmented lipopolysaccharide-induced lung injury and pulmonary edema following Klf4 depletion. Conclusion Our data show the key role of KLF4 in the regulation of VE-cadherin expression at the level of the AJs and in the acquisition of VE-cadherin-mediated endothelial barrier function. Thus, KLF4 maintains the integrity of AJs and prevents vascular leakage in response to inflammatory stimuli.
NANOG is a master transcription factor associated with the maintenance of stem cell pluripotency. Here, we demonstrate that transcription factor NANOG is expressed in cultured endothelial cells (ECs) and in a subset of tumor cell lines. Importantly, we provide evidence that WNT3A stimulation of ECs induces the transcription of NANOG which mediates the expression of vascular endothelial growth factor receptor-2, also known as fetal liver kinase-1 (FLK1). We defined ATTA as a minimal binding site for NANOG. Accordingly, a luciferase reporter assay showed that NANOG binds to and activates 4 ATTA binding sites identified in the FLK1 promoter after WNT3A stimulation. Consistent with this data, we found that, under basal conditions and in response to WNT3A stimulation, NANOG binding to these ATTA sequences markedly induced the expression of FLK1. Thus, our data indicate an essential role in angiogenesis for NANOG binding to these 4 ATTA sites. Surprisingly, NANOG depletion not only decreased FLK1 expression but also reduced cell proliferation and angiogenesis. These findings show the necessary and sufficient role of NANOG in inducing the transcription of IntroductionAngiogenesis, the sprouting of new capillaries from preexisting blood vessels, is not only required for embryonic development and wound healing but also contributes to pathologic processes, including atherosclerosis, diabetic retinopathy, and tumor progression. 1,2 In this regard, the activation of Wnt (Wingless) signaling in endothelial cells (ECs) has been shown to induce transcriptional events to regulate angiogenesis [3][4][5] ; however, the underlying mechanisms of these processes are not entirely clear. Beyond binding to the cytoplasmic domain of vascular endothelial-or E-cadherin, -catenin plays a key role in the transduction of Wnt signals by serving as a coactivator for the transcription factor T-cell factor/ lymphocyte enhancer binding factor (TCF/LEF-1). 6,7 The ligation of Wnt to the Frizzled receptor induces the inhibition of glycogen synthase kinase-3 that results in decreased phosphorylation of -catenin, thereby reduced proteolysis and degradation. [5][6][7] Stabilized -catenin translocates into the nucleus to associate with transcription factors of the TCF/LEF-1 family that can transactivate genes containing TCF/LEF-1 binding sequences. [5][6][7] Recent gene expression profiling has identified a role for Wnt signaling in EC commitment 8 and in control of vasculo-angiogenic aspects of embryonic development. [9][10][11][12][13][14][15] NANOG is a divergent homeobox transcription factor expressed in germ cells and pluripotent stem cells that is critical for morphogenesis and embryonic development. [16][17][18][19] Mouse embryos lacking nanog die between days embryonic (E) 3.5 and E5.5, before any vasculature has developed. 20,21 Nanog overexpression renders mouse embryonic stem (ES) cells independent of leukemia inhibitory factor/signal transducer and activator of transcription-3 stimulation for self-renewal. [17][18][19] Analyses of the ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.