Key Mechanisms of Early Lung Development

2007 ◽  
Vol 10 (5) ◽  
pp. 335-347 ◽  
Author(s):  
Jun Kimura ◽  
Gail H. Deutsch
Keyword(s):  
Respiratory Tract ◽  
Cell Fate ◽  
Target Genes ◽  
Critical Role ◽  
Hierarchical Classification ◽  
Branching Morphogenesis ◽  
Loss Of Function ◽  
Innovative Strategies ◽  
Downstream Target ◽  
Molecular Events

Lung morphogenesis requires the integration of multiple regulatory factors, which results in a functional air-blood interface required for gas exchange at birth. The respiratory tract is composed of endodermally derived epithelium surrounded by cells of mesodermal origin. Inductive signaling between these 2 tissue compartments plays a critical role in formation and differentiation of the lung, which is mediated by evolutionarily conserved signaling families used reiteratively during lung formation, including the fibroblast growth factor, hedgehog, retinoic acid, bone morphogenetic protein, and Wnt signaling pathways. Cells coordinate their response to these signaling proteins largely through transcription factors, which determine respiratory cell fate and pattern formation via the activation and repression of downstream target genes. Gain- and loss-of-function studies in null mutant and transgenic mice models have greatly facilitated the identification and hierarchical classification of these molecular programs. In this review, we highlight select molecular events that drive key phases of pulmonary development, including specification of a lung cell fate, primary lung bud formation, tracheoesophageal septation, branching morphogenesis, and proximal-distal epithelial patterning. Understanding the genetic pathways that regulate respiratory tract development is essential to provide insight into the pathogenesis of congenital anomalies and to develop innovative strategies to treat inherited and acquired lung disease.

Abstract 356: Krueppel-Like Factor 15 Regulates Wnt/β-Catenin Transcription and Controls Cardiac Progenitor Cell Fate in the Postnatal Heart

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Claudia Noack ◽  
Maria P Zafiriou ◽  
Anke Renger ◽  
Hans J Schaeffer ◽  
Martin W Bergmann ◽  
...  
Keyword(s):  
Cell Fate ◽  
Transcriptional Activation ◽  
Progenitor Cell ◽  
Cellular Localization ◽  
Target Genes ◽  
Critical Role ◽  
Isolated Cells ◽  
Cardiac Progenitor Cell

Wnt/β-catenin signaling controls adult heart remodeling partly by regulating cardiac progenitor cell (CPC) differentiation. We now identified and characterized a novel cardiac interaction of the transcription factor Krueppel-like factor 15 (KLF15) with the Wnt/β-catenin signaling on adult CPCs. In vitro mutation, reporter gene assays and co-localization studies revealed that KLF15 requires two distinct domains for nuclear localization and for repression of β-catenin-mediated transcription. KLF15 had no effect on β-catenin stability or cellular localization, but interacted with its co-factor TCF4, which is required for activation of β-catenin target gene expression. Moreover, increased TCF4 ubiquitination was induced by KLF15. In line with this finding we found KLF15 to interact with the Nemo-like kinase, which was shown to phosphorylate and target TCF4 for degradation. In vivo analyses of adult Klf15 functional knock-out (KO) vs. wild-type (WT) mice showed a cardiac β-catenin-mediated transcriptional activation and reduced TCF4 degradation along with cardiac dysfunction assessed by echocardiography (n=10). FACS analysis of the CPC enriched-population of KO vs. WT mice revealed a significant reduction of cardiogenic-committed precursors identified as Sca1+/αMHC+ (0.8±0.2% vs. 1.8±0.1%) and Tbx5+ (3.5±0.3% vs. 5.2±0.5%). In contrast, endothelial Sca1+/CD31+ cells were significantly higher in KO mice (11.3±0.4% vs. 8.6±0.4%; n≥9). In addition, Sca1+ isolated cells of Klf15 KO showed increased RNA expression of endothelial markers von Willebrand Factor, CD105, and Flk1 along with upregulation of β-catenin target genes. CPCs co-cultured on adult fibroblasts resulted in increased endothelial Flk1 cells and reduction of αMHC and Hand1 cardiogenic cells in KO vs. WT CPCs (n=9). Treating these co-cultures with Quercetin, an inhibitor of nuclear β-catenin, resulted in partial rescue of the observed phenotype. This study uncovers a critical role of KLF15 for the maintenance of cardiac tissue homeostasis. Via inhibition of β-catenin transcription, KLF15 controls cardiomyogenic cell fate similar to embryonic cardiogenesis. This knowledge may provide a tool for activation of endogenous CPCs in the postnatal heart.

Genetic evidence for the transcriptional-activating function of Homothorax during adult fly development

Development ◽  
2001 ◽  
Vol 128 (18) ◽  
pp. 3405-3413 ◽  
Author(s):  
Adi Inbal ◽  
Naomi Halachmi ◽  
Charna Dibner ◽  
Dale Frank ◽  
Adi Salzberg
Keyword(s):  
Transcriptional Activity ◽  
Target Genes ◽  
Genetic Evidence ◽  
In Vivo Studies ◽  
Loss Of Function ◽  
Native Form ◽  
Downstream Target ◽  
Activating Function

Homothorax (HTH) is a homeobox-containing protein, which plays multiple roles in the development of the embryo and the adult fly. HTH binds to the homeotic cofactor Extradenticle (EXD) and translocates it to the nucleus. Its function within the nucleus is less clear. It was shown, mainly by in vitro studies, that HTH can bind DNA as a part of ternary HTH/EXD/HOX complexes, but little is known about the transcription regulating function of HTH-containing complexes in the context of the developing fly. Here we present genetic evidence, from in vivo studies, for the transcriptional-activating function of HTH. The HTH protein was forced to act as a transcriptional repressor by fusing it to the Engrailed (EN) repression domain, or as a transcriptional activator, by fusing it to the VP16 activation domain, without perturbing its ability to translocate EXD to the nucleus. Expression of the repressing form of HTH in otherwise wild-type imaginal discs phenocopied hth loss of function. Thus, the repressing form was working as an antimorph, suggesting that normally HTH is required to activate the transcription of downstream target genes. This conclusion was further supported by the observation that the activating form of HTH caused typical hth gain-of-function phenotypes and could rescue hth loss-of-function phenotypes. Similar results were obtained with XMeis3, the Xenopus homologue of HTH, extending the known functional similarity between the two proteins. Competition experiments demonstrated that the repressing forms of HTH or XMeis3 worked as true antimorphs competing with the transcriptional activity of the native form of HTH. We also describe the phenotypic consequences of HTH antimorph activity in derivatives of the wing, labial and genital discs. Some of the described phenotypes, for example, a proboscis-to-leg transformation, were not previously associated with alterations in HTH activity. Observing the ability of HTH antimorphs to interfere with different developmental pathways may direct us to new targets of HTH. The HTH antimorph described in this work presents a new means by which the transcriptional activity of the endogenous HTH protein can be blocked in an inducible fashion in any desired cells or tissues without interfering with nuclear localization of EXD.

scholarly journals Antagonistic BMP–cWNT signaling in the cnidarian Nematostella vectensis reveals insight into the evolution of mesoderm

2017 ◽  
Vol 114 (28) ◽  
pp. E5608-E5615 ◽  
Author(s):  
Naveen Wijesena ◽  
David K. Simmons ◽  
Mark Q. Martindale
Keyword(s):  
Cell Fate ◽  
Target Genes ◽  
Bmp Signaling ◽  
Nematostella Vectensis ◽  
Beta Catenin ◽  
Molecular Signaling ◽  
Downstream Target ◽  
Evolutionary Innovation ◽  
Morphogenetic Protein ◽  
Cnidarian Nematostella Vectensis

Gastrulation was arguably the key evolutionary innovation that enabled metazoan diversification, leading to the formation of distinct germ layers and specialized tissues. Differential gene expression specifying cell fate is governed by the inputs of intracellular and/or extracellular signals. Beta-catenin/Tcf and the TGF-beta bone morphogenetic protein (BMP) provide critical molecular signaling inputs during germ layer specification in bilaterian metazoans, but there has been no direct experimental evidence for a specific role for BMP signaling during endomesoderm specification in the early branching metazoan Nematostella vectensis (an anthozoan cnidarian). Using forward transcriptomics, we show that beta-catenin/Tcf signaling and BMP2/4 signaling provide differential inputs into the cnidarian endomesodermal gene regulatory network (GRN) at the onset of gastrulation (24 h postfertilization) in N. vectensis. Surprisingly, beta-catenin/Tcf signaling and BMP2/4 signaling regulate a subset of common downstream target genes in the GRN in opposite ways, leading to the spatial and temporal differentiation of fields of cells in the developing embryo. Thus, we show that regulatory interactions between beta-catenin/Tcf signaling and BMP2/4 signaling are required for the specification and determination of different embryonic regions and the patterning of the oral–aboral axis in Nematostella. We also show functionally that the conserved “kernel” of the bilaterian heart mesoderm GRN is operational in N. vectensis, which reinforces the hypothesis that the endoderm and mesoderm in triploblastic bilaterians evolved from the bifunctional endomesoderm (gastrodermis) of a diploblastic ancestor, and that slow rhythmic contractions might have been one of the earliest functions of mesodermal tissue.

Abstract 206: Stem Cell-derived Exosomes Induce Cardiac Repair via mRNA Modification

2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Prabhu Mathiyalagan ◽  
Yaxuan Liang ◽  
Adriano S Martins ◽  
Douglas W Losordo ◽  
Roger J Hajjar ◽  
...  
Keyword(s):  
Stem Cell ◽  
Myocardial Ischemia ◽  
Target Genes ◽  
Critical Role ◽  
Cell Communication ◽  
Target Cells ◽  
Mouse Heart ◽  
Loss Of Function

Exosomes are cell-derived nanovesicles that carry and shuttle microRNAs (miRNAs) to mediate cell-cell communication. Vast majority of cell types including cardiac myocytes and progenitors actively secrete exosomes, whose miRNA contents are altered after physiological or pathological changes such as myocardial ischemia (MI). In this new study, we have discovered that chemical modification to mRNAs is a novel regulator of ischemia-induced gene expression changes in the heart. We hypothesized that the benefits of human CD34 + stem cell-derived exosomes (CD34exo) are mediated by mRNA modifications in the target cells via miRNA delivery. MiRNA profiling and bioinformatic analysis identified that CD34exo is selectively enriched with a number of miRNAs that directly target genes implicated in regulation of mRNA modifications. Interestingly, under myocardial ischemia, there was a significant increase in mRNA modifications in the mouse heart, which was decreased by about 70% with CD34exo-treatment. In line with the in vivo MI data, in vitro hypoxic stimulation in neonatal / adult rodent myocytes and non-myocytes increased mRNA modifications and controls known regulators of those mRNA modifications. Loss-of-function studies for regulators of mRNA modifications attenuated hypoxia-induced changes to epitranscriptome indicating important roles for these molecules under stress conditions. Finally, using gain-of-function and loss-of-function studies, we demonstrate that miR-126, one of the most enriched miRNAs in CD34exo, plays a critical role in regulating the mRNA modifications. We conclude that miRNAs enriched in CD34exo mediate their cardioprotective effect at least in part, by regulating the mRNA epitranscriptome of the target cell. Our new data suggests hypoxia as a novel regulator of the mRNA epitranscriptome and provides novel insights to post-transcriptional gene regulation in the heart.

Multiple roles for activated LEF/TCF transcription complexes during hair follicle development and differentiation

Development ◽  
1999 ◽  
Vol 126 (20) ◽  
pp. 4557-4568 ◽  
Author(s):  
R. DasGupta ◽  
E. Fuchs
Keyword(s):  
Hair Follicle ◽  
Cell Fate ◽  
Target Genes ◽  
Inducible Promoter ◽  
Hair Shaft ◽  
Precursor Cells ◽  
Beta Catenin ◽  
Hair Cycle ◽  
Outer Root Sheath ◽  
Downstream Target

LEF/TCF DNA-binding proteins act in concert with activated beta -catenin, the product of Wnt signaling, to transactivate downstream target genes. To probe the role of activated LEF/TCF transcription factor complexes in hair follicle morphogenesis and differentiation, we engineered mice harboring TOPGAL, a beta -galactosidase gene under the control of a LEF/TCF and beta -catenin inducible promoter. In mice, TOPGAL expression was directly stimulated by a stabilized form of beta -catenin, but was also dependent upon LEF1/TCF3 in skin. During embryogenesis, TOPGAL activation occurred transiently in a subset of LEF1-positive cells of pluripotent ectoderm and underlying mesenchyme. Downgrowth of initiated follicles proceeded in the absence of detectable TOPGAL expression, even though LEF1 was still expressed. While proliferative matrix cells expressed the highest levels of Lef1 mRNAs, LEF1 concentrated in the precursor cells to the hair shaft, where TOPGAL expression was co-induced with hair-specific keratin genes containing LEF/TCF-binding motifs. LEF1 and TOPGAL expression ceased during catagen and telogen, but reappeared at the start of the postnatal hair cycle, concomitant with precortex formation. In contrast to hair shaft precursor cells, postnatal outer root sheath expressed TCF3, but not TOPGAL. TCF3 was also expressed in the putative follicle stem cells, and while TOPGAL was generally silent in this compartment, it was stimulated at the start of the hair cycle in a fashion that appeared to be dependent upon stabilization of beta -catenin. Taken together, our findings demonstrate that LEF1/TCF3 is necessary but not sufficient for TOPGAL activation, revealing the existence of positive and negative regulators of these factors in the skin. Furthermore, our findings unveil the importance of activated LEF/TCF complexes at distinct times in hair development and cycling when changes in cell fate and differentiation commitments take place.

scholarly journals Mechanisms in Endocrinology: Notch signaling in skeletal health and disease

2013 ◽  
Vol 168 (6) ◽  
pp. R95-R103 ◽  
Author(s):  
Stefano Zanotti ◽  
Ernesto Canalis
Keyword(s):  
Notch Signaling ◽  
Cell Fate ◽  
Target Genes ◽  
Skeletal Development ◽  
Alagille Syndrome ◽  
Notch Signaling Pathway ◽  
Loss Of Function ◽  
Skeletal Health ◽  
Notch Ligand ◽  
Ligand Interactions

Notch receptors are single-pass transmembrane proteins that determine cell fate. Upon Notch ligand interactions, proteolytic cleavages release the Notch intracellular domain, which translocates to the nucleus to regulate the transcription of target genes, including Hairy enhancer of split (Hes) and Hes related to YRPW motif (Hey). Notch is critical for skeletal development and activity of skeletal cells, and dysregulation of Notch signaling is associated with human diseases affecting the skeleton. Inherited or sporadic mutations in components of the Notch signaling pathway are associated with spondylocostal dysostosis, spondylothoracic dysostosis and recessive brachydactyly, diseases characterized by skeletal patterning defects. Inactivating mutations of the Notch ligandJAG1or ofNOTCH2are associated with Alagille syndrome, and activating mutations inNOTCH2are associated with Hajdu–Cheney syndrome (HCS). Individuals affected by HCS exhibit osteolysis in distal phalanges and osteoporosis. NOTCH is activated in selected tumors, such as osteosarcoma, and in breast cancer cells that form osteolytic bone metastases. In conclusion, Notch regulates skeletal development and bone remodeling, and gain- or loss-of-function mutations of Notch signaling result in important skeletal diseases.

scholarly journals Induction of Human Liver X Receptor α Gene Expression Via an Autoregulatory Loop Mechanism

2002 ◽  
Vol 16 (3) ◽  
pp. 506-514 ◽  
Author(s):  
Yu Li ◽  
Charles Bolten ◽  
B. Ganesh Bhat ◽  
Jessica Woodring-Dietz ◽  
Suzhen Li ◽  
...  
Keyword(s):  
Gene Expression ◽  
Target Genes ◽  
Regulatory Element ◽  
Critical Role ◽  
Cell Types ◽  
Plasma Lipoproteins ◽  
Type I ◽  
Type Ii ◽  
Downstream Target ◽  
X Receptors

Abstract The liver X receptors (LXRs), members of the nuclear receptor superfamily, play an important role in controlling lipid homeostasis by activating several genes involved in reverse cholesterol transport. These include members of the ATP binding cassette (ABC) superfamily of transporter proteins ABCA1 and ABCG1, surface constituents of plasma lipoproteins like apolipoprotein E, and cholesterol ester transport protein. They also play an important role in fatty acid metabolism by activating the sterol regulatory element-binding protein 1c gene. Here, we identify human LXRα (hLXRα) as an autoinducible gene. Induction in response to LXR ligands is observed in multiple human cell types including macrophages and occurs within 2–4 h. Analysis of the hLXRα promoter revealed three LXR response elements (LXREs); one exhibits strong affinity for both LXRα:RXR and LXRβ:RXR (a type I LXRE), and deletion and mutational studies indicate it plays a critical role in LXR-mediated induction. The other two LXREs are identical to each other, exist within highly conserved Alu repeats, and exhibit selective binding to LXRα:RXR (type II LXREs). In transfections, the type I LXRE acts as a strong mediator of both LXRα and LXRβ activity, whereas the type II LXRE acts as a weaker and selective mediator of LXRα activity. Our data suggest a model in which LXR ligands trigger an autoregulatory loop leading to selective induction of hLXRα gene expression. This would lead to increased hLXRα levels and transcription of its downstream target genes such as ABCA1, providing a simple yet exquisite mechanism for cells to respond to LXR ligands and cholesterol loading.

scholarly journals Identification of a Mouse Homolog of the Human BTEB2Transcription Factor as a β-Catenin-Independent Wnt-1-Responsive Gene

2001 ◽  
Vol 21 (2) ◽  
pp. 562-574 ◽  
Author(s):  
Lisa Taneyhill Ziemer ◽  
Diane Pennica ◽  
Arnold J. Levine
Keyword(s):  
Cell Line ◽  
Cell Fate ◽  
Target Genes ◽  
Wild Type Mouse ◽  
Subtractive Hybridization ◽  
Parental Cell ◽  
Mammary Tissue ◽  
Parental Cell Line ◽  
Mouse Homolog ◽  
Downstream Target

ABSTRACT The Wnt/Wg signaling pathway functions during development to regulate cell fate determination and patterning in various organisms. Two pathways are reported to lie downstream of Wnt signaling in vertebrates. The canonical pathway relies on the activation of target genes through the β-catenin–Lef/TCF complex, while the noncanonical pathway employs the activation of protein kinase C (PKC) and increases in intracellular calcium to induce target gene expression. cDNA subtractive hybridization between a cell line that overexpresses Wnt-1 (C57MG/Wnt-1) and the parental cell line (C57MG) was performed to identify downstream target genes of Wnt-1 signaling. Among the putative Wnt-1 target genes, we have identified a mouse homolog of the gene encoding human transcription factor basic transcription element binding protein 2 (mBTEB2). ThemBTEB2 transcript is found at high levels in mammary tissue taken from a transgenic mouse overexpressing Wnt-1 (both tissue prior to active proliferation and tumor tissue) but is barely detectable in wild-type mouse mammary glands. The regulation of mBTEB2 by Wnt-1 signaling in tissue culture occurs through a β-catenin–Lef/TCF-independent mechanism, as it is instead partially regulated by PKC. The Wnt-1-induced, PKC-dependent activation of mouse BTEB2 in C57MG cells, as well as the ability of Wnt-1 to stabilize β-catenin in these cells, is consistent with the hypothesis that both the noncanonical and canonical Wnt pathways are activated concomitantly in the same cell. These results suggest that mBTEB2 is a biologically relevant target of Wnt-1 signaling that is activated through a β-catenin-independent, PKC-sensitive pathway in response to Wnt-1.

scholarly journals Akt-mediated Ephexin1–Ras interaction promotes oncogenic Ras signaling and colorectal and lung cancer cell proliferation

2021 ◽  
Vol 12 (11) ◽  
Author(s):  
Jeeho Kim ◽  
Young Jin Jeon ◽  
Sung-Chul Lim ◽  
Joohyun Ryu ◽  
Jung-Hee Lee ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Target Genes ◽  
Critical Role ◽  
Survival Rates ◽  
Tumor Grade ◽  
Mapk Signaling ◽  
Ras Signaling ◽  
Poor Overall Survival ◽  
Downstream Target ◽  
Oncogenic Ras

AbstrctEphexin1 was reported to be highly upregulated by oncogenic Ras, but the functional consequences of this remain poorly understood. Here, we show that Ephexin1 is highly expressed in colorectal cancer (CRC) and lung cancer (LC) patient tissues. Knockdown of Ephexin1 markedly inhibited the cell growth of CRC and LC cells with oncogenic Ras mutations. Ephexin1 contributes to the positive regulation of Ras-mediated downstream target genes and promotes Ras-induced skin tumorigenesis. Mechanically, Akt phosphorylates Ephexin1 at Ser16 and Ser18 (pSer16/18) and pSer16/18 Ephexin1 then interacts with oncogenic K-Ras to promote downstream MAPK signaling, facilitating tumorigenesis. Furthermore, pSer16/18 Ephexin1 is associated with both an increased tumor grade and metastatic cases of CRC and LC, and those that highly express pSer16/18 exhibit poor overall survival rates. These data indicate that Ephexin1 plays a critical role in the Ras-mediated CRC and LC and pSer16/18 Ephexin1 might be an effective therapeutic target for CRC and LC.

Treatment with bevacizumab (BEV) upregulates expression of the transcription factor Sp1 and its downstream target genes in human carcinoid cells: Molecular basis of the synergistic antiangiogenic activity of bevacizumab and mithramycin A (MIT)

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 15031-15031 ◽  
Author(s):  
J. Zhang ◽  
Z. Jia ◽  
L. Wang ◽  
Q. Li ◽  
L. Xiangdong ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Growth Factor ◽  
Nude Mice ◽  
Target Genes ◽  
Critical Role ◽  
Angiogenic Factors ◽  
Downstream Target ◽  
Transcription Factor Sp1 ◽  
Mithramycin A ◽  
The Impact

15031 Background: Our previous studies show that human carcinoid cells overexpress pro-angiogenic factors, vascular endothelial growth factor A (VEGF), and transcription factor Sp1 plays a critical role in VEGF inducible and constitutive expression. However, the impact of antiangiogenic therapy on the Sp1/VEGF pathway remains unclear. Method: Groups of 10 athymic BALB/c nude mice were implanted with 1.5 million human H727 carcinoid cells. Treatment with VEGF neutralizing monoclonal antibody, BEV, MIT, or BEV + MIT was initiated once implanted tumor reached 4 mm in size. Result: Treatment with BEV, suppressed human carcinoid growth in nude mice (tumor size at week 5 1280 mm3 vs 480 mm3; p < 0.001). Gene expression analyses revealed that this treatment substantially upregulated the expression of Sp1 (7 folds) and its downstream target genes, including VEGF (5 folds) and epidermal growth factor receptor (4 folds), in tumor tissues, whereas it did not have this effect on carcinoid cells in culture. Treatment with mithramycin A, an Sp1 inhibitor, suppressed the expression of Sp1 and its downstream target genes in both cell culture and tumors growing in nude mice. Median survival of mice treated with PBS, BEV, MIT, and BEV + MIT groups were 88, 112, 121, and >160 days respectively (p < 0.001). Combined treatment with bevacizumab and mithramycin A produced synergistic tumor suppression, which was consistent with suppression of the expression of Sp1 and its downstream target genes. Conclusion: Treatment with bevacizumab may block VEGF function but activate the pathway of its expression via positive feedback. Given the fact that Sp1 is an important regulator of the expression of multiple angiogenic factors, bevacizumab-initiated upregulation of Sp1 and subsequent overexpression of its downstream target genes may affect the potential angiogenic phenotype and effectiveness of antiangiogenic strategies for human carcinoid. No significant financial relationships to disclose.

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