Molecular Cell Biology Unit

Gent, Belgium

Molecular Cell Biology Unit

Gent, Belgium
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Herzog D.,Institute of Cell Biology | Herzog D.,Max Planck Institute of Immunobiology | Loetscher P.,Institute of Cell Biology | van Hengel J.,Molecular Cell Biology Unit | And 8 more authors.
Journal of Neuroscience | Year: 2011

The regulation of adherens junctions (AJs) is critical for multiple events during CNS development, including the formation and maintenance of the neuroepithelium. We have addressed the role of the small GTPase RhoA in the developing mouse nervous system using tissue-specific conditional gene ablation. Weshow that, in the spinal cord neuroepithelium, RhoA is essential to localize N-cadherin and β-catenin to AJs and maintain apical-basal polarity of neural progenitor cells. Ablation of RhoA caused the loss of AJs and severe abnormalities in the organization of cells within the neuroepithelium, including decreased neuroepithelial cell proliferation and premature cell-cycle exit, reduction of the neural stem cell pool size, and the infiltration of neuroepithelial cells into the lumen of the ventricle. We also show that, in the absence of RhoA, its effector, mammalian diaphanous-related formin1 (mDia1), does not localize to apical AJs in which it likely stabilizes intracellular adhesion by promoting local actin polymerization and microtubule organization. Furthermore, expressing a dominant-negative form of mDia1 in neural stem/progenitor cells results in a similar phenotype compared with that of the RhoA conditional knock-out, namely the loss of AJs and apical polarity. Together, our data show that RhoA signaling is necessary for AJ regulation and for the maintenance of mammalian neuroepithelium organization preventing precocious cell-cycle exit and differentiation. © 2011 the authors.

Gheldof A.,Unit of Molecular and Cellular Oncology | Gheldof A.,Ghent University | Hulpiau P.,Ghent University | Van Roy F.,Ghent University | And 5 more authors.
Cellular and Molecular Life Sciences | Year: 2012

ZEB1 and ZEB2, which are members of the ZEB family of transcription factors, play a pivotal role in the development of the vertebrate embryo. However, recent evidence shows that both proteins can also drive the process of epithelial-mesenchymal transition during malignant cancer progression. The understanding of how both ZEBs act as transcription factors opens up new possibilities for future treatment of advanced carcinomas. This review gives insight into the molecular mechanisms that form the basis of the multitude of cellular processes controlled by both ZEB factors. By using an evolutionary approach, we analyzed how the specific organization of the different domains and regulatory sites in ZEB1 and ZEB2 came into existence. On the basis of this analysis, a detailed overview is provided of the different cofactors and post-translational mechanisms that are associated with ZEB protein functionality. © Springer Basel AG 2012.

Jackson B.,Copenhagen University | Peyrollier K.,Copenhagen University | Pedersen E.,Copenhagen University | Basse A.,Copenhagen University | And 15 more authors.
Molecular Biology of the Cell | Year: 2011

RhoA is a small guanosine-5'-triphosphatase (GTPase) suggested to be essential for cytokinesis, stress fiber formation, and epithelial cell - cell contacts. In skin, loss of RhoA was suggested to underlie pemphigus skin blistering. To analyze RhoA function in vivo, we generated mice with a keratinocyte-restricted deletion of the RhoA gene. Despite a severe reduction of cofilin and myosin light chain (MLC) phosphorylation, these mice showed normal skin development. Primary RhoA-null keratinocytes, however, displayed an increased percentage of multinucleated cells, defective maturation of cell - cell contacts. Furthermore we observed increased cell spreading due to impaired RhoA-ROCK (Rho-associated protein kinase)-MLC phosphatase-MLC - mediated cell contraction, independent of Rac1. Rho-inhibiting toxins further increased multinucleation of RhoA-null cells but had no significant effect on spreading, suggesting that RhoB and RhoC have partially overlapping functions with RhoA. Loss of RhoA decreased directed cell migration in vitro caused by reduced migration speed and directional persistence. These defects were not related to the decreased cell contraction and were independent of ROCK, as ROCK inhibition by Y27632 increased directed migration of both control and RhoA-null keratinocytes. Our data indicate a crucial role for RhoA and contraction in regulating cell spreading and a contraction-independent function of RhoA in keratinocyte migration. In addition, our data show that RhoA is dispensable for skin development. © 2011 Jackson et al.

Verstraeten B.,Ghent University | Sanders E.,Ghent University | Sanders E.,Molecular Cell Biology Unit | Van Hengel J.,Molecular Cell Biology Unit | And 2 more authors.
BMC Developmental Biology | Year: 2010

Background. The development of teeth is the result of interactions between competent mesenchyme and epithelium, both of which undergo extensive morphogenesis. The importance of cell adhesion molecules in morphogenesis has long been acknowledged but remarkably few studies have focused on the distribution and function of these molecules in tooth development. Results. We analyzed the expression pattern of an important epithelial cadherin, E-cadherin, during the formation of first-generation teeth as well as replacement teeth in the zebrafish, using in situ hybridization and whole mount immunostaining to reveal mRNA expression and protein distribution. E-cadherin was detected in every layer of the enamel organ during the different stages of tooth development, but there were slight differences between first-generation and replacement teeth in the strength and distribution of the signal. The dental papilla, which is derived from the mesenchyme, did not show any expression. Remarkably, the crypts surrounding the functional teeth showed an uneven distribution of E-cadherin throughout the pharyngeal region. Conclusions. The slight differences between E-cadherin expression in zebrafish teeth and developing mouse and human teeth are discussed in the light of fundamental differences in structural and developmental features of the dentition between zebrafish and mammals. Importantly, the uninterrupted expression of E-cadherin indicates that down-regulation of E-cadherin is not required for formation of an epithelial tooth bud. Further research is needed to understand the role of other cell adhesion systems during the development of teeth and the formation of replacement teeth. © 2010 Verstraeten et al; licensee BioMed Central Ltd.

Pieters T.,Ghent University | Pieters T.,Molecular and Cellular Oncology Unit | van Roy F.,Ghent University | van Roy F.,Molecular Cell Biology Unit
Journal of Cell Science | Year: 2014

Pluripotent embryonic stem cells (ESCs) can self-renew or differentiate into any cell type within an organism. Here, we focus on the roles of cadherins and catenins - their cytoplasmic scaffold proteins - in the fate, maintenance and differentiation of mammalian ESCs. E-cadherin is a master stem cell regulator that is required for both mouse ESC (mESC) maintenance and differentiation. Ecadherin interacts with key components of the naive stemness pathway and ablating it prevents stem cells from forming welldifferentiated teratomas or contributing to chimeric animals. In addition, depleting E-cadherin converts naive mouse ESCs into primed epiblast-like stem cells (EpiSCs). In line with this, a mesenchymal-to-epithelial transition (MET) occurs during reprogramming of somatic cells towards induced pluripotent stem cells (iPSCs), leading to downregulation of N-cadherin and acquisition of high E-cadherin levels. β-catenin exerts a dual function; it acts in cadherin-based adhesion and in WNT signaling and, although WNT signaling is important for stemness, the adhesive function of β-catenin might be crucial for maintaining the naive state of stem cells. In addition, evidence is rising that other junctional proteins are also important in ESC biology. Thus, precisely regulated levels and activities of several junctional proteins, in particular E-cadherin, safeguard naive pluripotency and are a prerequisite for complete somatic cell reprogramming. © 2014. Published by The Company of Biologists Ltd.

Verstraeten B.,Ghent University | Van Hengel J.,Molecular Cell Biology Unit | Van Hengel J.,Ghent University | Huysseune A.,Ghent University
PLoS ONE | Year: 2016

We analyzed the protein distribution of two cadherin-Associated molecules, plakoglobin and β-catenin, during the different stages of tooth development and tooth replacement in zebrafish. Plakoglobin was detected at the plasma membrane already at the onset of tooth development in the epithelial cells of the tooth. This pattern remained unaltered during further tooth development. The mesenchymal cells only showed plakoglobin from cytodifferentiation onwards. Plakoglobin 1a morpholino-injected embryos showed normal tooth development with proper initiation and differentiation. Although plakoglobin is clearly present during normal odontogenesis, the loss of plakoglobin 1a does not influence tooth development. β-catenin was found at the cell borders of all cells of the successional lamina but also in the nuclei of surrounding mesenchymal cells. Only membranous, not nuclear, β-catenin, was found during morphogenesis stage. However, during cytodifferentiation stage, both nuclear and membrane-bound β-catenin was detected in the layers of the enamel organ as well as in the differentiating odontoblasts. Nuclear β-catenin is an indication of an activated Wnt pathway, therefore suggesting a possible role for Wnt signalling during zebrafish tooth development and replacement. © 2016 Verstraeten et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Verstraeten B.,Ghent University | Sanders E.,Ghent University | Sanders E.,Molecular Cell Biology Unit | Huysseune A.,Ghent University
Methods in Molecular Biology | Year: 2012

Tooth development is increasingly being studied in a variety of vertebrate model organisms, each contributing its own perspective to our understanding of dental diversity. In situ hybridization and immunohistochemistry are well-established and frequently used techniques to study the presence of mRNA and protein. Here, we describe a protocol for whole mount immunohistochemistry and in situ hybridization that can be applied to all stages of zebrafish development and dissected bony parts. The description of these protocols is followed by the outline of a quick decalcification method and the procedure for embedding in epoxy resin to obtain serial sections with high histological quality. © 2012 Springer Science+Business Media, LLC.

Verstraeten B.,Ghent University | Sanders E.,Ghent University | Sanders E.,Molecular Cell Biology Unit | van Hengel J.,Molecular Cell Biology Unit | And 2 more authors.
Journal of Applied Ichthyology | Year: 2010

Although the importance of cell adhesion in morphogenesis is already known for quite some time, there are remarkably few studies on the distribution and function of adhesion molecules in tooth development. We have chosen the zebrafish to study the role of specific cell adhesion molecules in the development and renewal of teeth. Zebrafish lack an oral dentition but have pharyngeal teeth which are renewed throughout life. Here we focus on the expression of E (epithelial)-cadherin during the development of the first tooth to develop in the dentition, 'initiator tooth' 4V1. E-cadherin is expressed exclusively in the pharyngeal epithelium and in the enamel organ throughout all stages of development of this first-generation tooth. Further studies are needed to compare this expression pattern with protein distribution, both in this and other first-generation teeth as well as in replacement teeth. © 2010 Blackwell Verlag, Berlin.

Grelet S.,University of Reims Champagne Ardenne | Andries V.,Ghent University | Andries V.,Molecular Cell Biology Unit | Polette M.,University of Reims Champagne Ardenne | And 16 more authors.
Journal of Pathology | Year: 2015

We have explored the role of the human NANOS3 gene in lung tumour progression. We show that NANOS3 is over-expressed by invasive lung cancer cells and is a prognostic marker for non-small cell lung carcinomas (NSCLCs). NANOS3 gene expression is restricted in testis and brain and is regulated by epigenetic events. It is up-regulated in cultured cells undergoing epithelial - mesenchymal transition (EMT). NANOS3 over-expression in human NSCLC cell lines enhances their invasiveness by up-regulating EMT, whereas its silencing induces mesenchymal - epithelial transition. NANOS3 represses E-cadherin at the transcriptional level and up-regulates vimentin post-transcriptionally. Also, we show that NANOS3 binds mRNAs encoding vimentin and regulates the length of their poly(A) tail. Finally, NANOS3 can also protect vimentin mRNA from microRNA-mediated repression. We thus demonstrate a role for NANOS3 in the acquisition of invasiveness by human lung tumour cells and propose a new mechanism of post-transcriptional regulation of EMT. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

PubMed | Molecular Cell Biology Unit
Type: Journal Article | Journal: Investigative ophthalmology & visual science | Year: 2012

Development of the ocular anterior segment depends largely on periocular mesenchyme cells, which are derived predominantly from neural crest cells (NCC). Specific and differential cell adhesion is expected to be instrumental in induction, migration, and differentiation of NCC. As p120 catenin (ctn) is an important component of cadherin-catenin cell adhesion complexes, we assessed its role in development of the anterior segment structure.We generated conditional p120ctn(fl/fl);Wnt1Cre knockout mice and studied the effect of this gene ablation on eye development in vivo. In addition, p120ctn was knocked down in vitro.Wnt1Cre-mediated deletion of floxed p120ctn alleles in NCC resulted in serious ocular anterior segment dysgenesis (ASD), including iridocorneal angle closure, complete anterior chamber obliteration, iris and ciliary body hypoplasia, corneal malformation and opacity, and glaucoma-like defects. A completely penetrant phenotype was visible approximately three weeks after birth, but histologic defects were obvious at embryonal day 18.5 (E18.5). Neither migration of NCC nor expression of key transcription factors appeared to be affected. In contrast, the N-cadherin expression pattern was changed significantly in iridocorneal angle cells and corneal endothelium. A human trabecular meshwork cell line in which p120ctn was knocked down also showed decreased expression levels of N-cadherin and -catenin at the plasma membrane, but no defect in cell migration.p120ctn has a critical role in ocular mesenchyme development. Loss of p120ctn and the associated N-cadherin downregulation in NCC leads to ASD without affecting cell migration. p120ctn abnormalities might have a role in the pathophysiology of mammalian eye development.

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