Foxc1 is required for early stage telencephalic vascular development

Genome-wide profiling of angiogenic cis-regulatory elements unravels cis-regulatory SNPs for vascular abnormality

Angiogenesis is extensively involved in embryonic development and requires complex regulation networks, whose defects can cause a variety of vascular abnormalities. Cis-regulatory elements control gene expression at all developmental stages, but they have not been studied or profiled in angiogenesis yet. In this study, we exploited public DNase-seq and RNA-seq datasets from a VEGFA-stimulated in vitro angiogenic model, and carried out an integrated analysis of the transcriptome and chromatin accessibility across the entire process. Totally, we generated a bank of 47,125 angiogenic cis-regulatory elements with promoter (marker by H3K4me3) and/or enhancer (marker by H3K27ac) activities. Motif enrichment analysis revealed that these angiogenic cis-regulatory elements interacted preferentially with ETS family TFs. With this tool, we performed an association study using our WES data of TAPVC and identified rs199530718 as a cis-regulatory SNP associated with disease risk. Altogether, this study generated a genome-wide bank of angiogenic cis-regulatory elements and illustrated its utility in identifying novel cis-regulatory SNPs for TAPVC, expanding new horizons of angiogenesis as well as vascular abnormality genetics.

The cerebrofacial metameric syndromes: An embryological review and proposal of a novel classification scheme

The cerebrofacial metameric syndromes are a group of congenital syndromes that result in vascular malformations throughout specific anatomical distributions of the brain, cranium and face. Multiple reports of patients with high-flow or low-flow vascular malformations following a metameric distribution have supported this idea. There has been much advancement in understanding of segmental organization and cell migration since the concept of metameric vascular syndromes was first proposed. We aim to give an updated review of these embryological considerations and then propose a more detailed classification system for these syndromes, predominately incorporating the contribution of neural crest cells and somitomeres to the pharyngeal arches.

Foxc1a regulates zebrafish vascular integrity and brain vascular development through targeting amotl2a and ctnnb1

Accumulating evidences have pointed that foxc1a is essential for vascular development and integrity maintenance through regulating the expression of downstream genes and interacting with signaling pathways. However, the underling cellular and molecular mechanisms of foxc1a in regulating vascular development remain undetermined. Based on two different foxc1a mutant zebrafish lines (foxc1a^nju18 and foxc1a^nju19 which generated predicted truncated foxc1a proteins with 50aa and 315aa respectively), we found that around 30 % of foxc1a^nju18 zebrafish exhibited severe vascular developmental defects with obvious hemorrhage in hindbrain and trunk at embryonic stages. Confocal imaging analysis revealed that the formation of middle cerebral vein (MCeV), intra-cerebral central arteries (CtAs) and dorsal longitudinal vein (DLV) of brain vessels was significantly blocked in foxc1a^nju18enbryos. Injection of exogenous full length and foxc1a^nju19 truncated foxc1a mRNA both rescued the deficiency of foxc1a^nju18 embryos. Transcriptome analysis revealed 186 DEGs in foxc1a^nju18 zebrafish among which amotl2a and ctnnb1 expression were reduced and functionally associated with adherens junctions. Dual-Luciferase assays validated amotl2a and ctnnb1 were both directly transactivated by foxc1a. Rescue experiments demonstrated that amotl2a was mainly responsible for the vascular integrity caused by foxc1a mutation and also coordinated with ctnnb1 to regulate brain vascular development. Our data point to a novel clue that foxc1a regulates vascular integrity and brain vascular development through targeting amotl2a and ctnnb1.

Elevated TGFβ signaling contributes to ocular anterior segment dysgenesis in Col4a1 mutant mice

Ocular anterior segment dysgenesis (ASD) refers to a collection of developmental disorders affecting the anterior structures of the eye. Although a number of genes have been implicated in the etiology of ASD, the underlying pathogenetic mechanisms remain unclear. Mutations in genes encoding collagen type IV alpha 1 (COL4A1) and alpha 2 (COL4A2) cause Gould syndrome, a multi-system disorder that often includes ocular manifestations such as ASD and glaucoma. COL4A1 and COL4A2 are abundant basement membrane proteins that provide structural support to tissues and modulate signaling through interactions with other extracellular matrix proteins, growth factors, and cell surface receptors. In this study, we used a combination of histological, molecular, genetic and pharmacological approaches to demonstrate that altered TGFβ signaling contributes to ASD in mouse models of Gould syndrome. We show that TGFβ signaling was elevated in anterior segments from Col4a1 mutant mice and that genetically reducing TGFβ signaling partially prevented ASD. Notably, we identified distinct roles for TGFβ1 and TGFβ2 in ocular defects observed in Col4a1 mutant mice. Importantly, we show that pharmacologically promoting type IV collagen secretion or reducing TGFβ signaling ameliorated ocular pathology in Col4a1 mutant mice. Overall, our findings demonstrate that altered TGFβ signaling contributes to COL4A1-related ocular dysgenesis and implicate this pathway as a potential therapeutic target for the treatment of Gould syndrome.

Post-Transcriptional Regulation of Molecular Determinants during Cardiogenesis

Cardiovascular development is initiated soon after gastrulation as bilateral precardiac mesoderm is progressively symmetrically determined at both sides of the developing embryo. The precardiac mesoderm subsequently fused at the embryonic midline constituting an embryonic linear heart tube. As development progress, the embryonic heart displays the first sign of left-right asymmetric morphology by the invariably rightward looping of the initial heart tube and prospective embryonic ventricular and atrial chambers emerged. As cardiac development progresses, the atrial and ventricular chambers enlarged and distinct left and right compartments emerge as consequence of the formation of the interatrial and interventricular septa, respectively. The last steps of cardiac morphogenesis are represented by the completion of atrial and ventricular septation, resulting in the configuration of a double circuitry with distinct systemic and pulmonary chambers, each of them with distinct inlets and outlets connections. Over the last decade, our understanding of the contribution of multiple growth factor signaling cascades such as Tgf-beta, Bmp and Wnt signaling as well as of transcriptional regulators to cardiac morphogenesis have greatly enlarged. Recently, a novel layer of complexity has emerged with the discovery of non-coding RNAs, particularly microRNAs and lncRNAs. Herein, we provide a state-of-the-art review of the contribution of non-coding RNAs during cardiac development. microRNAs and lncRNAs have been reported to functional modulate all stages of cardiac morphogenesis, spanning from lateral plate mesoderm formation to outflow tract septation, by modulating major growth factor signaling pathways as well as those transcriptional regulators involved in cardiac development.

Activation of the LINC00242/miR-141/FOXC1 axis underpins the development of gastric cancer

Background

Long non-coding RNAs (LncRNAs) are a class of newly identified transcripts recognized as critical governors of gene expression during human carcinogenesis, whereas their tumor-suppressive or tumor-promoting effects on gastric cancer (GC) are required for further investigation. In the study, we identify the expression pattern of a novel lncRNA LINC00242 in GC and its possible permissive role in the development of GC.

Methods

The study included 68 pairs of GC and adjacent normal gastric tissue samples. The viability, migration, and invasion of cultured human GC cells HGC27 were evaluated by CCK-8 and Transwell chamber assays. In vitro tube formation of human brain microvascular endothelial cells (HBMVECs) in HGC27 cell coculture was detected. The regulatory network of LINC00242/miR-141/FOXC1 was verified using dual luciferase reporter gene assay and RNA immunoprecipitation (RIP) assay. Subcutaneous xenografts of HGC27 cells were performed in nude mice.

Results

LINC00242 was highly expressed in GC tissues and cells and contributed to poor prognosis. LINC00242 knockdown inhibited HGC27 cell viability, migration and invasion, and tube formation of HBMVECs. LINC00242 interacted with miR-141 and positively regulated FOXC1, a target gene of miR-141. LINC00242 knockdown was partially lost in HGC27 cells upon miR-141 inhibition or FOXC1 overexpression. The tumor-promoting effect of LINC00242 on GC was demonstrated in nude mice.

Conclusion

Taken together, the present study demonstrates the oncogenic role of the LINC00242/miR-141/FOXC1 axis in GC, highlighting a theoretical basis for GC treatment.

foxc1 is required for embryonic head vascular smooth muscle differentiation in zebrafish

Vascular smooth muscle of the head derives from neural crest, but developmental mechanisms and early transcriptional drivers of the vSMC lineage are not well characterized. We find that in early development, the transcription factor foxc1b is expressed in mesenchymal cells that associate with the vascular endothelium. Using timelapse imaging, we observe that foxc1b expressing mesenchymal cells differentiate into acta2 expressing vascular mural cells. We show that in zebrafish, while foxc1b is co-expressed in acta2 positive smooth muscle cells that associate with large diameter vessels, it is not co-expressed in capillaries where pdgfrβ positive pericytes are located. In addition to being an early marker of the lineage, foxc1 is essential for vSMC differentiation; we find that foxc1 loss of function mutants have defective vSMC differentiation and that early genetic ablation of foxc1b or acta2 expressing populations blocks vSMC differentiation. Furthermore, foxc1 is expressed upstream of acta2 and is required for acta2 expression in vSMCs. Using RNA-Seq we determine an enriched intersectional gene expression profile using dual expression of foxc1b and acta2 to identify novel vSMC markers. Taken together, our data suggests that foxc1 is a marker of vSMCs and plays a critical functional role in promoting their differentiation.

A dynamic and integrated epigenetic program at distal regions orchestrates transcriptional responses to VEGFA

Cell behaviors are dictated by epigenetic and transcriptional programs. Little is known about how extracellular stimuli modulate these programs to reshape gene expression and control cell behavioral responses. Here, we interrogated the epigenetic and transcriptional response of endothelial cells to VEGFA treatment and found rapid chromatin changes that mediate broad transcriptomic alterations. VEGFA-responsive genes were associated with active promoters, but changes in promoter histone marks were not tightly linked to gene expression changes. VEGFA altered transcription factor occupancy and the distal epigenetic landscape, which profoundly contributed to VEGFA-dependent changes in gene expression. Integration of gene expression, dynamic enhancer, and transcription factor occupancy changes induced by VEGFA yielded a VEGFA-regulated transcriptional regulatory network, which revealed that the small MAF transcription factors are master regulators of the VEGFA transcriptional program and angiogenesis. Collectively these results revealed that extracellular stimuli rapidly reconfigure the chromatin landscape to coordinately regulate biological responses.

Deletion of 6p25.3 Is Associated with Cerebrovascular Dolichoectasia: Report of 2 Cases

Developmental dolichoectasia of the intracranial vessels is a rare occurrence. The authors report 2 sibling pediatric patients who were born with 6p25.3 deletion, associated with carotid and vertebrobasilar dolichoectasia. MRI imaging of both children showed asymptomatic elongation and dilation of the vertebrobasilar system and "kissing" carotid arteries. A microarray analysis was also performed for both patients, which identified a 1.5-Mb deletion of 6p25.3 covering 15 genes including FOXC1, which has been implicated in defects in vascular morphogenesis.

Transcription factor Foxc1 is involved in anterior part of cranial base formation

The cranial base is a structure mainly formed through endochondral ossification and integrated into the craniofacial complex, which acts as an underlying platform for the developing brain. Foxc1 is an indispensable regulator during intramembranous and endochondral ossification. In this study, we found that the spontaneous loss of Foxc1 function in a mouse (congenital hydrocephalous), Foxc1^ch/ch , demonstrated the anterior cranial base defects, including unossified presphenoid and lack of middle part of the basisphenoid bone. Hypoplastic presphenoid primordial cartilage (basal portion of the trabecular cartilage [bTB]) and a lack of the middle part of basisphenoid primordial cartilage (the hypophyseal cartilage) were consistently observed at earlier developmental stage. Foxc1 was expressed robustly and ubiquitously in undifferentiated mesenchyme of the cranial base-forming area in E11.0 wild-type fetuses. Once chondrogenesis commenced, the expression was downregulated and later limited to the perichondrium. Detection of transcripts of Collagen type2 A1 (Col2a1) revealed that both bTB and the anterior part of the hypophyseal cartilage developing anterior to the persistent epithelial stalk of the anterior lobe of the pituitary gland were suppressed in the Foxc1^ch/ch . Proliferation activity of chondrocyte precursor cells was higher in the Foxc1^ch/ch . Loss of Foxc1 function only in the neural crest cell lineage (Wnt1-cre;Foxc1^ch/flox ) showed ossification of the posterior part of the hypophyseal cartilage derived from the mesoderm. These findings suggest that Foxc1 is an important regulator to further chondrogenesis and initiate the ossification of the presphenoid and basisphenoid bones.

Knockdown of long non-coding RNA XIST increases blood-tumor barrier permeability and inhibits glioma angiogenesis by targeting miR-137

Antiangiogenic therapy plays a significant role in combined glioma treatment. However, poor permeability of the blood–tumor barrier (BTB) limits the transport of chemotherapeutic agents, including antiangiogenic drugs, into tumor tissues. Long non-coding RNAs (lncRNAs) have been implicated in various diseases, especially malignant tumors. The present study found that lncRNA X-inactive-specific transcript (XIST) was upregulated in endothelial cells that were obtained in a BTB model in vitro. XIST knockdown increased BTB permeability and inhibited glioma angiogenesis. The analysis of the mechanism of action revealed that the reduction of XIST inhibited the expression of the transcription factor forkhead box C1 (FOXC1) and zonula occludens 2 (ZO-2) by upregulating miR-137. FOXC1 decreased BTB permeability by increasing the promoter activity and expression of ZO-1 and occludin, and promoted glioma angiogenesis by increasing the promoter activity and expression of chemokine (C–X–C motif) receptor 7b (CXCR7). Overall, the present study demonstrates that XIST plays a pivotal role in BTB permeability and glioma angiogenesis, and the inhibition of XIST may be a potential target for the clinical management of glioma.

FOXC1: an emerging marker and therapeutic target for cancer

The Forkhead box C1 (FOXC1) transcription factor is involved in normal embryonic development and regulates the development and function of many organs. Most recently, a large body of literature has shown that FOXC1 plays a critical role in tumor development and metastasis. Clinical studies have demonstrated that elevated FOXC1 expression is associated with poor prognosis in many cancer subtypes, such as basal-like breast cancer (BLBC). FOXC1 is highly and specifically expressed in BLBC as opposed to other breast cancer subtypes. Its functions in breast cancer have been extensively explored. This review will summarize current knowledge on the function and regulation of FOXC1 in tumor development and progression with a focus on BLBC as well as the implications of these new findings in cancer diagnosis and treatment.

Cerebrovascular defects in Foxc1 mutants correlate with aberrant WNT and VEGF-A pathways downstream of retinoic acid from the meninges

Growth and maturation of the cerebrovasculature is a vital event in neocortical development however mechanisms that control cerebrovascular development remain poorly understood. Mutations in or deletions that include the FOXC1 gene are associated with congenital cerebrovascular anomalies and increased stroke risk in patients. Foxc1 mutant mice display severe cerebrovascular hemorrhage at late gestational ages. While these data demonstrate Foxc1 is required for cerebrovascular development, its broad expression in the brain vasculature combined with Foxc1 mutant's complex developmental defects have made it difficult to pinpoint its function(s). Using global and conditional Foxc1 mutants, we find 1) significant cerebrovascular growth defects precede cerebral hemorrhage and 2) expression of Foxc1 in neural crest-derived meninges and brain pericytes, though not endothelial cells, is required for normal cerebrovascular development. We provide evidence that reduced levels of meninges-derived retinoic acid (RA), caused by defects in meninges formation in Foxc1 mutants, is a major contributing factor to the cerebrovascular growth defects in Foxc1 mutants. We provide data that suggests that meninges-derived RA ensures adequate growth of the neocortical vasculature via regulating expression of WNT pathway proteins and neural progenitor derived-VEGF-A. Our findings offer the first evidence for a role of the meninges in brain vascular development and provide new insight into potential causes of cerebrovascular defects in patients with FOXC1 mutations.