Jolanda van Hengel

Publications of Jolanda van Hengel

• Loss of αT-catenin alters the hybrid adhering junctions in the heart and leads to dilated cardiomyopathy and ventricular arrhythmia following acute ischemia.

  Authors: Jifen Li, Steven Goossens, Jolanda van Hengel, Erhe Gao, Lan Cheng, Koen Tyberghein, Xiying Shang, Riet De Rycke, Frans van Roy, Glenn L Radice

  Journal of cell science. 03/2012; 125(Pt 4):1058-67.

  It is generally accepted that the intercalated disc (ICD) required for mechano-electrical coupling in the heart consists of three distinct junctional complexes: adherens junctions, desmosomes and gapIt is generally accepted that the intercalated disc (ICD) required for mechano-electrical coupling in the heart consists of three distinct junctional complexes: adherens junctions, desmosomes and gap junctions. However, recent morphological and molecular data indicate a mixing of adherens junctional and desmosomal components, resulting in a 'hybrid adhering junction' or 'area composita'. The α-catenin family member αT-catenin, part of the N-cadherin-catenin adhesion complex in the heart, is the only α-catenin that interacts with the desmosomal protein plakophilin-2 (PKP2). Thus, it has been postulated that αT-catenin might serve as a molecular integrator of the two adhesion complexes in the area composita. To investigate the role of αT-catenin in the heart, gene targeting technology was used to delete the Ctnna3 gene, encoding αT-catenin, in the mouse. The αT-catenin-null mice are viable and fertile; however, the animals exhibit progressive cardiomyopathy. Adherens junctional and desmosomal proteins were unaffected by loss of αT-catenin, with the exception of the desmosomal protein PKP2. Immunogold labeling at the ICD demonstrated in the αT-catenin-null heart a preferential reduction of PKP2 at the area composita compared with the desmosome. Furthermore, gap junction protein Cx43 was reduced at the ICD, including its colocalization with N-cadherin. Gap junction remodeling in αT-catenin-knockout hearts was associated with an increased incidence of ventricular arrhythmias after acute ischemia. This novel animal model demonstrates for the first time how perturbation in αT-catenin can affect both PKP2 and Cx43 and thereby highlights the importance of understanding the crosstalk between the junctional proteins of the ICD and its implications for arrhythmogenic cardiomyopathy.

• Functions of p120ctn in development and disease.

  Authors: Tim Pieters, Jolanda van Hengel, Frans van Roy

  Frontiers in bioscience : a journal and virtual library. 01/2012; 17:760-83.

  p120 catenin (p120ctn), a component of the cadherin-catenin complex, was the first member to be identified in a most interesting subfamily of the Armadillo family. Several p120ctn isoforms arep120 catenin (p120ctn), a component of the cadherin-catenin complex, was the first member to be identified in a most interesting subfamily of the Armadillo family. Several p120ctn isoforms are generated by alternative splicing. These isoforms fulfill pleiotropic functions according to their subcellular localization: modulating the turnover rate of membrane-bound cadherins, regulating the activation of small Rho GTPases in the cytoplasm, and modulating nuclear transcription. Over the last two decades, knowledge of p120ctn has grown remarkably, and this has been achieved in part by using different animal models. At least in frog and mammals, p120ctn is essential for normal development and homeostasis. Here we will discuss the effects of different p120ctn isoforms on cadherin turnover and on signaling in the cytoplasm and the nucleus. We will also elaborate on the structure and function of other members of the p120ctn subfamily: ARVCF, p0071 and delta-catenin. Finally, we will overview the respective roles of p120ctn family members in pathological processes, and particularly in cancer as p120ctn is frequently.

• Functions of p120ctn isoforms in cell-cell adhesion and intracellular signaling.

  Authors: Tim Pieters, Frans van Roy, Jolanda van Hengel

  Frontiers in bioscience : a journal and virtual library. 01/2012; 17:1669-94.

  The functions of many organs depend on the generation of an epithelium. The transition from a set of loosely connected nonpolarized cells to organized sheets of closely associated polarizedThe functions of many organs depend on the generation of an epithelium. The transition from a set of loosely connected nonpolarized cells to organized sheets of closely associated polarized epithelial cells requires the assembly of specialized cell junctions. In vertebrates, three major types of junctions are responsible for epithelial integrity: adherens junctions, tight junctions, and desmosomes. p120 catenin (p120ctn) is an Armadillo family member and a component of the cadherin-catenin complex in the adherens junction. It fulfils pleiotropic functions according to its subcellular localization: modulating the turnover rate of membrane-bound cadherins, regulating the activation of small RhoGTPases in the cytoplasm, and modulating nuclear transcription. Over the last two decades, knowledge of p120ctn obtained from in vitro experiments has been confirmed and extended by using different animal models. It has become clear that p120ctn is essential for normal development and homeostasis, at least in frog and mammals. p120ctn is a Src substrate that can be phosphorylated at different tyrosine, serine and threonine residues and can dock various kinases and phosphatases. Thereby, p120ctn regulates the phosphorylation status and the junctional stability of the cadherin-catenin complex. Multiple p120ctn isoforms are generated by alternative splicing, which allows the translation to be initiated from four start codons and enables the inclusion of four alternatively used exons. We will discuss the effects of different p120ctn isoforms on cadherin turnover and intracellular signaling, in particular RhoGTPase activity and phosphorylation events.

• Megakaryocyte-specific RhoA deficiency causes macrothrombocytopenia and defective platelet activation in hemostasis and thrombosis.

  Authors: Irina Pleines, Ina Hagedorn, Shuchi Gupta, Frauke May, Lidija Chakarova, Jolanda van Hengel, Stefan Offermanns, Georg Krohne, Christoph Kleinschnitz, Cord Brakebusch, Bernhard Nieswandt

  Blood. 11/2011; 119(4):1054-63.

  Vascular injury initiates rapid platelet activation that is critical for hemostasis, but it also may cause thrombotic diseases, such as myocardial infarction or ischemic stroke. Reorganizations ofVascular injury initiates rapid platelet activation that is critical for hemostasis, but it also may cause thrombotic diseases, such as myocardial infarction or ischemic stroke. Reorganizations of the platelet cytoskeleton are crucial for platelet shape change and secretion and are thought to involve activation of the small GTPase RhoA. In this study, we analyzed the in vitro and in vivo consequences of megakaryocyte- and platelet-specific RhoA gene deletion in mice. We found a pronounced macrothrombocytopenia in RhoA-deficient mice, with platelet counts of approximately half that of wild-type controls. The mutant cells displayed an altered shape but only a moderately reduced life span. Shape change of RhoA-deficient platelets in response to G(13)-coupled agonists was abolished, and it was impaired in response to G(q) stimulation. Similarly, RhoA was required for efficient secretion of α and dense granules downstream of G(13) and G(q). Furthermore, RhoA was essential for integrin-mediated clot retraction but not for actomyosin rearrangements and spreading of activated platelets on fibrinogen. In vivo, RhoA deficiency resulted in markedly prolonged tail bleeding times but also significant protection in different models of arterial thrombosis and in a model of ischemic stroke. Together, these results establish RhoA as an important regulator of platelet function in thrombosis and hemostasis.

• Efficient and User-Friendly Pluripotin-based Derivation of Mouse Embryonic Stem Cells.

  Authors: Tim Pieters, Lieven Haenebalcke, Tino Hochepied, Jinke D'Hont, Jody J Haigh, Frans van Roy, Jolanda van Hengel

  Stem cell reviews. 10/2011;

  Classic derivation of mouse embryonic stem (ES) cells from blastocysts is inefficient, strain-dependent, and requires expert skills. Over recent years, several major improvements have greatlyClassic derivation of mouse embryonic stem (ES) cells from blastocysts is inefficient, strain-dependent, and requires expert skills. Over recent years, several major improvements have greatly increased the success rate for deriving mouse ES cell lines. The first improvement was the establishment of a user-friendly and reproducible medium-alternating protocol that allows isolation of ES cells from C57BL/6 transgenic mice with efficiencies of up to 75%. A recent report describes the use of this protocol in combination with leukemia inhibitory factor and pluripotin treatment, which made it possible to obtain ES cells from F1 strains with high efficiency. We report modifications of these protocols for user-friendly and reproducible derivation of mouse ES cells with efficiencies of up to 100%. Our protocol involves a long initial incubation of primary outgrowths from blastocysts with pluripotin, which results in the formation of large spherical outgrowths. These outgrowths are morphologically distinct from classical inner cell mass (ICM) outgrowths and can be easily picked and trypsinized. Pluripotin was omitted after the first trypsinization because we found that it blocks attachment of ES cells to the feeder layer and its removal facilitated formation of ES cell colonies. The newly established ES cells exhibited normal karyotypes and generated chimeras. In summary, our user-friendly modified protocol allows formation of large spherical ICM outgrowths in a robust and reliable manner. These outgrowths gave rise to ES cell lines with success rates of up to 100%.

• The small GTPase RhoA is required to maintain spinal cord neuroepithelium organization and the neural stem cell pool.

  Authors: Dominik Herzog, Pirmin Loetscher, Jolanda van Hengel, Sebastian Knüsel, Cord Brakebusch, Verdon Taylor, Ueli Suter, João B Relvas

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 03/2011; 31(13):5120-30.

  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 theThe 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. We show 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.

• RhoA is dispensable for skin development, but crucial for contraction and directed migration of keratinocytes.

  Authors: Ben Jackson, Karine Peyrollier, Esben Pedersen, Astrid Basse, Richard Karlsson, Zhipeng Wang, Tine Lefever, Alexandra M Ochsenbein, Gudula Schmidt, Klaus Aktories, Alanna Stanley, Fabio Quondamatteo, Markus Ladwein, Klemens Rottner, Jolanda van Hengel, Cord Brakebusch

  Molecular biology of the cell. 01/2011; 22(5):593-605.

  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 toRhoA 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.

• The transcriptional repressor Kaiso localizes at the mitotic spindle and is a constituent of the pericentriolar material.

  Authors: Adelheid Soubry, Katrien Staes, Eef Parthoens, Sam Noppen, Christophe Stove, Pieter Bogaert, Jolanda van Hengel, Frans van Roy

  PloS one. 01/2010; 5(2):e9203.

  Kaiso is a BTB/POZ zinc finger protein known as a transcriptional repressor. It was originally identified through its in vitro association with the Armadillo protein p120ctn. Subcellular localizationKaiso is a BTB/POZ zinc finger protein known as a transcriptional repressor. It was originally identified through its in vitro association with the Armadillo protein p120ctn. Subcellular localization of Kaiso in cell lines and in normal and cancerous human tissues revealed that its expression is not restricted to the nucleus. In the present study we monitored Kaiso's subcellular localization during the cell cycle and found the following: (1) during interphase, Kaiso is located not only in the nucleus, but also on microtubular structures, including the centrosome; (2) at metaphase, it is present at the centrosomes and on the spindle microtubules; (3) during telophase, it accumulates at the midbody. We found that Kaiso is a genuine PCM component that belongs to a pericentrin molecular complex. We analyzed the functions of different domains of Kaiso by visualizing the subcellular distribution of GFP-tagged Kaiso fragments throughout the cell cycle. Our results indicate that two domains are responsible for targeting Kaiso to the centrosomes and microtubules. The first domain, designated SA1 for spindle-associated domain 1, is located in the center of the Kaiso protein and localizes at the spindle microtubules and centrosomes; the second domain, SA2, is an evolutionarily conserved domain situated just before the zinc finger domain and might be responsible for localizing Kaiso towards the centrosomal region. Constructs containing both SA domains and Kaiso's aminoterminal BTB/POZ domain triggered the formation of abnormal centrosomes. We also observed that overexpression of longer or full-length Kaiso constructs led to mitotic cell arrest and frequent cell death. Knockdown of Kaiso accelerated cell proliferation. Our data reveal a new target for Kaiso at the centrosomes and spindle microtubules during mitosis. They also strongly imply that Kaiso's function as a transcriptional regulator might be linked to the control of the cell cycle and to cell proliferation in cancer.

• Zebrafish teeth as a model for repetitive epithelial morphogenesis: dynamics of E-cadherin expression.

  Authors: Barbara Verstraeten, Ellen Sanders, Jolanda van Hengel, Ann Huysseune

  BMC developmental biology. 01/2010; 10:58.

  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 inThe 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. 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. 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.

• Alternatively activated macrophages engage in homotypic and heterotypic interactions through IL-4 and polyamine-induced E-cadherin/catenin complexes.

  Authors: Jan Van den Bossche, Pieter Bogaert, Jolanda van Hengel, Christopher J Guerin, Geert Berx, Kiavash Movahedi, Rafael Van den Bergh, Anna Pereira-Fernandes, Jan M C Geuns, Hanspeter Pircher, Pierre Dorny, Johan Grooten, Patrick De Baetselier, Jo A Van Ginderachter

  Blood. 10/2009;

  Alternatively activated macrophages (AAMs), triggered by IL-4 and IL-13, play a modulating role during Th2 cytokine-driven pathologies, but their molecular armament remains poorly characterized.Alternatively activated macrophages (AAMs), triggered by IL-4 and IL-13, play a modulating role during Th2 cytokine-driven pathologies, but their molecular armament remains poorly characterized. Here, we established E-cadherin (Cdh1) as a selective marker for IL-4/IL-13-exposed mouse and human macrophages, which is STAT6-dependently induced during polarized Th2 responses associated with Taenia crassiceps helminth infections or allergic airway inflammation. The IL-4-dependent, arginase-1/ornithine decarboxylase-mediated production of polyamines is important for maximal Cdh1 induction, unveiling a novel mechanism for IL-4-dependent gene transcription. At the macrophage surface, E-cadherin forms a functional complex with the catenins that accumulates at sites of cell contact. Macrophage-specific deletion of the Cdh1 gene illustrates the implication of E-cadherin in IL-4-driven macrophage fusion and heterotypic interactions with CD103(+) and KLRG1(+) T cells. This study identifies the E-cadherin/catenin complex as a discriminative, partly polyamine-regulated feature of IL-4/IL-13-exposed alternatively activated macrophages that contributes to homotypic and heterotypic cellular interactions.

• Endoplasmic Reticulum Quality Control: a new mechanism of E-cadherin regulation and its implication in cancer.

  Authors: Joana Simões-Correia, Joana Figueiredo, Carla Oliveira, Jolanda van Hengel, Raquel Seruca, Frans van Roy, Gianpaolo Suriano

  Human molecular genetics. 10/2008;

  E-cadherin is critical for the maintenance of tissue architecture and is a major component of adherens junctions. Its role in tumour development is well established, with many human carcinomasE-cadherin is critical for the maintenance of tissue architecture and is a major component of adherens junctions. Its role in tumour development is well established, with many human carcinomas exhibiting E-cadherin loss at the invasive front. In many invasive carcinomas the mechanisms leading to E-cadherin loss remain elusive. Here, we hypothesise that mechanisms of protein quality control play a key role in E-cadherin regulation. As a cell model system, we used CHO cells stably expressing E-cadherin germline missense mutations R749W and E757K, which are associated with hereditary diffuse gastric cancer. An abnormal pattern of E-cadherin expression was observed, with protein accumulating mainly in the ER. We demonstrated that E-cadherin missense mutants are subjected to Endoplasmic Reticulum Quality Control (ERQC) and that their loss is due to ER-associated degradation (ERAD). Treatment of these mutant cells with specific chemical chaperones restored E-cadherin to the cell membrane and rescued its function. We show that ERQC plays a major role in E-cadherin regulation and propose that overcoming this regulation may represent an approach to rescue E-cadherin expression and functionality in cancer.

• Plakophilin-3-deficient mice develop hair coat abnormalities and are prone to cutaneous inflammation.

  Authors: Tatyana Sklyarova, Stefan Bonné, Petra D'Hooge, Geertrui Denecker, Steven Goossens, Riet De Rycke, Gaetan Borgonie, Michael Bösl, Frans van Roy, Jolanda van Hengel

  The Journal of investigative dermatology. 07/2008; 128(6):1375-85.

  We generated mice deficient in plakophilin-3 (PKP3), a member of the Armadillo-repeat family and a component of desmosomes and stress granules in epithelial cells. In these mice, several subsets ofWe generated mice deficient in plakophilin-3 (PKP3), a member of the Armadillo-repeat family and a component of desmosomes and stress granules in epithelial cells. In these mice, several subsets of hair follicles (HFs) had morphological abnormalities, and the majority of awl and auchene hair shafts had fewer medullar air columns. Desmosomes were absent from the basal layer of the outer root sheath of HFs and from the matrix cells that are in contact with dermal papillae. In the basal layer of PKP3-null epidermis, densities of desmosomes and adherens junctions were remarkably altered. Compensatory changes in several junctional proteins were observed. PKP3-null mice housed in conventional facilities were prone to dermatitis. Our animal model provides in vivo evidence that PKP3 plays a critical role in morphogenesis of HFs and shafts and in limiting inflammatory responses in the skin.

• Continuous cell injury promotes hepatic tumorigenesis in cdc42-deficient mouse liver.

  Authors: Jolanda van Hengel, Petra D'Hooge, Bart Hooghe, Xunwei Wu, Louis Libbrecht, Rita De Vos, Fabio Quondamatteo, Martina Klempt, Cord Brakebusch, Frans van Roy

  Gastroenterology. 03/2008; 134(3):781-92.

  BACKGROUND & AIMS: The Rho small guanosine triphosphatase Cdc42 is critical for diverse cellular functions, including regulation of actin organization, cell polarity, intracellular membraneBACKGROUND & AIMS: The Rho small guanosine triphosphatase Cdc42 is critical for diverse cellular functions, including regulation of actin organization, cell polarity, intracellular membrane trafficking, transcription, cell-cycle progression, and cell transformation. This implies that Cdc42 might be required for liver function. METHODS: Mice in which Cdc42 was ablated in hepatocytes and bile duct cells were generated by Cre-loxP technology. Livers were examined by histologic, immunohistochemical, ultrastructural, and serum analysis to define the effect of loss of Cdc42 on liver structure. RESULTS: Mice lacking Cdc42 in their hepatocytes were born at Mendelian ratios. They did not show increased mortality but showed chronic jaundice. They developed hepatomegaly soon after birth, and signs of liver transformation, such as formation of nodules and tumors, became visible macroscopically at age 6 months. Hepatocellular carcinoma was observed 8 months after birth. Tumors grew slowly and lacked expression of nuclear beta-catenin. Lung metastases were observed at the late stage of carcinogenesis. Immunofluorescent examination and electron microscopy revealed severe defects in the liver. At the age of 2 months, the canaliculi between hepatocytes were greatly enlarged, although the tight junctions flanking the canaliculi appeared normal. Regular liver plates were absent. E-cadherin expression pattern and gap junction localization were distorted. Analysis of serum samples indicated cholestasis. CONCLUSIONS: We describe a mouse model in which chronic liver disease leads to hepatocarcinogenesis.

• A unique and specific interaction between alphaT-catenin and plakophilin-2 in the area composita, the mixed-type junctional structure of cardiac intercalated discs.

  Authors: Steven Goossens, Barbara Janssens, Stefan Bonné, Riet De Rycke, Filip Braet, Jolanda van Hengel, Frans van Roy

  Journal of cell science. 07/2007; 120(Pt 12):2126-36.

  Alpha-catenins play key functional roles in cadherin-catenin cell-cell adhesion complexes. We previously reported on alphaT-catenin, a novel member of the alpha-catenin protein family. alphaT-cateninAlpha-catenins play key functional roles in cadherin-catenin cell-cell adhesion complexes. We previously reported on alphaT-catenin, a novel member of the alpha-catenin protein family. alphaT-catenin is expressed predominantly in cardiomyocytes, where it colocalizes with alphaE-catenin at the intercalated discs. Whether alphaT- and alphaE-catenin have specific or synergistic functions remains unknown. In this study we used the yeast two-hybrid approach to identify specific functions of alphaT-catenin. An interaction between alphaT-catenin and plakophilins was observed and subsequently confirmed by co-immunoprecipitation and colocalization. Interaction with the amino-terminal part of plakophilins appeared to be specific for the central ;adhesion-modulation' domain of alphaT-catenin. In addition, we showed, by immuno-electron microscopy, that desmosomal proteins in the heart localize not only to the desmosomes in the intercalated discs but also at adhering junctions with hybrid composition. We found that in the latter junctions, endogenous plakophilin-2 colocalizes with alphaT-catenin. By providing an extra link between the cadherin-catenin complex and intermediate filaments, the binding of alphaT-catenin to plakophilin-2 is proposed to be a means of modulating and strengthening cell-cell adhesion between cardiac muscle cells. This could explain the devastating effect of plakophilin-2 mutations on cell junction stability in intercalated discs, which lead to cardiac muscle malfunction.

• Truncated isoform of mouse alphaT-catenin is testis-restricted in expression and function.

  Authors: Steven Goossens, Barbara Janssens, Griet Vanpoucke, Riet De Rycke, Jolanda van Hengel, Frans van Roy

  The FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 04/2007; 21(3):647-55.

  AlphaT-catenin is a recently identified member of the alpha-catenin family of cell-cell adhesion molecules. For decades it was thought that alpha-catenins mediate solid cell-cell adhesion by linkingAlphaT-catenin is a recently identified member of the alpha-catenin family of cell-cell adhesion molecules. For decades it was thought that alpha-catenins mediate solid cell-cell adhesion by linking the cadherin-mediated cell-cell adhesion complex with the actin cytoskeleton. However, the roles of alpha-catenins in this classical adhesion model have been questioned recently. AlphaT-catenin has a restricted expression pattern, in contrast to the ubiquitously expressed alphaE-catenin. High levels of alphaT-catenin were detected in heart and testis. Northern and Western blot experiments indicated that besides the standard full-length alphaT-catenin transcript, smaller alternative transcripts are expressed in testis. We report the cloning of two alternative transcripts of the mouse alphaT-catenin gene (transcript-B and -X), both of which are expressed in a testis-restricted manner from two putative alternative promoters. Alternative transcript-X encodes a smaller protein, isoform-X, which lacks the amino-terminal beta-catenin binding domain of the standard mouse alphaT-catenin protein, and is therefore unable to restore cell-cell adhesion in an alpha-catenin-negative colon carcinoma cell line. Immunohistochemical analysis showed specific localization of the alphaT-catenin isoform-X in the differentiating germ cells. In contrast to the standard full-length alphaT-catenin protein, this shortened isoform-X can bind to l-afadin, an important component of the nectin/afadin/ponsin adhesion complex that reportedly is essential for spermatogenesis.

• Diverse functions of p120ctn in tumors.

  Authors: Jolanda van Hengel, Frans van Roy

  Biochimica et biophysica acta. 02/2007; 1773(1):78-88.

  p120ctn is a member of the Armadillo protein family. It stabilizes the cadherin-catenin adhesion complex at the plasma membrane, but also has additional roles in the cytoplasm and nucleus. Extensivep120ctn is a member of the Armadillo protein family. It stabilizes the cadherin-catenin adhesion complex at the plasma membrane, but also has additional roles in the cytoplasm and nucleus. Extensive alternative mRNA splicing and multiple phosphorylation sites generate additional complexity. Evidence is emerging that complete loss, downregulation or mislocalization of p120ctn correlates with progression of different types of human tumors. It remains to be determined whether a causal relationship exists between specific isoform expression, subcellular localization or selective phosphorylation of p120ctn on the one hand and tumor prognosis on the other.

• Nuclear translocation of alphaN-catenin by the novel zinc finger transcriptional repressor ZASC1.

  Authors: Sven Bogaerts, Ann Vanlandschoot, Jolanda van Hengel, Frans van Roy

  Experimental cell research. 12/2005; 311(1):1-13.

  Alpha-catenins anchor the transmembrane cell-cell adhesion molecule E-cadherin indirectly to the actin cytoskeleton through interaction with beta-catenin or plakoglobin. Three differentAlpha-catenins anchor the transmembrane cell-cell adhesion molecule E-cadherin indirectly to the actin cytoskeleton through interaction with beta-catenin or plakoglobin. Three different alpha-catenins are known at present: alphaE-, alphaT-, and alphaN-catenin. Despite their different expression patterns, no functional differences between the alpha-catenins are known. In a yeast two-hybrid screening with alphaN-catenin as bait, we identified the Cys(2)-His2 zinc finger protein ZASC1. The mRNA and protein of ZASC1 were ubiquitously expressed in various cell lines and human tissues. Our results suggest an association of the ZASC1 protein with DNA, and luciferase reporter assays revealed that ZASC1 is a transcriptional repressor. Upon transient overexpression, the ZASC1 protein localized in the nucleus, to where it was able to recruit cytoplasmic alphaN-catenin. Neither the highly related alphaE-catenin nor alphaT-catenin interacted with ZASC1. By interchanging parts of alphaN-catenin and alphaE-catenin cDNAs, we were able to narrow down the interaction region of alphaN-catenin to two limited amino-terminal regions. On the other hand, the interaction of ZASC1 with alphaN-catenin can be mediated by the domain comprising zinc fingers six to eight of ZASC1. The interaction and nuclear cotranslocation of a neural alpha-catenin with a putative proto-oncogene product as reported here provides novel insights into the signaling functions of alpha-catenins.

• Cdc42 is not essential for filopodium formation, directed migration, cell polarization, and mitosis in fibroblastoid cells.

  Authors: Aleksandra Czuchra, Xunwei Wu, Hannelore Meyer, Jolanda van Hengel, Timm Schroeder, Robert Geffers, Klemens Rottner, Cord Brakebusch

  Molecular biology of the cell. 11/2005; 16(10):4473-84.

  Cdc42 is a small GTPase involved in the regulation of the cytoskeleton and cell polarity. To test whether Cdc42 has an essential role in the formation of filopodia or directed cell migration, weCdc42 is a small GTPase involved in the regulation of the cytoskeleton and cell polarity. To test whether Cdc42 has an essential role in the formation of filopodia or directed cell migration, we generated Cdc42-deficient fibroblastoid cells by conditional gene inactivation. We report here that loss of Cdc42 did not affect filopodium or lamellipodium formation and had no significant influence on the speed of directed migration nor on mitosis. Cdc42-deficient cells displayed a more elongated cell shape and had a reduced area. Furthermore, directionality during migration and reorientation of the Golgi apparatus into the direction of migration was decreased. However, expression of dominant negative Cdc42 in Cdc42-null cells resulted in strongly reduced directed migration, severely reduced single cell directionality, and complete loss of Golgi polarization and of directionality of protrusion formation toward the wound, as well as membrane blebbing. Thus, our data show that besides Cdc42 additional GTPases of the Rho-family, which share GEFs with Cdc42, are involved in the establishment and maintenance of cell polarity during directed migration.

• Expression and nuclear location of the transcriptional repressor Kaiso is regulated by the tumor microenvironment.

  Authors: Adelheid Soubry, Jolanda van Hengel, Eef Parthoens, Cecile Colpaert, Eric Van Marck, David Waltregny, Albert B Reynolds, Frans van Roy

  Cancer research. 04/2005; 65(6):2224-33.

  Kaiso is a BTB/POZ zinc finger protein originally described as an interaction partner of p120ctn. In cultured cell lines, Kaiso is found almost exclusively in the nucleus, where it generally acts asKaiso is a BTB/POZ zinc finger protein originally described as an interaction partner of p120ctn. In cultured cell lines, Kaiso is found almost exclusively in the nucleus, where it generally acts as a transcriptional repressor. Here, we describe the first in situ immunolocalization studies of Kaiso expression in normal and cancerous tissues. Surprisingly, we found striking differences between its behavior in monolayers of different cell lines, three-dimensional cell culture systems, and in vivo. Although nuclear localization was sometimes observed in tissues, Kaiso was more often found in the cytoplasm, and in some cell types it was absent. In general, Kaiso and p120ctn did not colocalize in the nucleus. To examine this phenomenon more carefully, tumor cells exhibiting strong nuclear Kaiso staining in vitro were injected into nude mice and grown as xenografts. The latter showed a progressive translocation of Kaiso towards the cytoplasm over time, and even complete loss of expression, especially in the center of the tumor nodules. When xenografted tumors were returned to cell culture, Kaiso was re-expressed and was once again found in the nucleus. Translocation of Kaiso to the cytoplasm and down-regulation of its levels were also observed under particular experimental conditions in vitro, such as formation of spheroids and acini. These data strongly imply an unexpected influence of the microenvironment on Kaiso expression and localization. As transcriptional repression is a nuclear event, this phenomenon is likely a crucial factor in the regulation of Kaiso function.

• Implication of the MAGI-1b/PTEN signalosome in stabilization of adherens junctions and suppression of invasiveness.

  Authors: Larissa Kotelevets, Jolanda van Hengel, Erik Bruyneel, Marc Mareel, Frans van Roy, Eric Chastre

  The FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 02/2005; 19(1):115-7.

  We recently established the critical role of the lipid phosphatase activity of the PTEN tumor suppressor in stabilizing cell-cell contacts and suppressing invasiveness. To delineate the effectorWe recently established the critical role of the lipid phosphatase activity of the PTEN tumor suppressor in stabilizing cell-cell contacts and suppressing invasiveness. To delineate the effector systems involved, we investigated the interaction of PTEN with E-cadherin junctional complexes in kidney and colonic epithelial cell lines. PTEN and the p85 regulatory subunit of phosphatidylinositol 3-OH kinase (PI3K) co-immunoprecipitated with E-cadherin and catenins. By using a yeast two-hybrid assay, we demonstrated that PTEN interacted indirectly with beta-catenin by binding the scaffolding protein MAGI-1b. This model was corroborated in various ways in mammalian cells. Ectopic expression of MAGI-1b potentiated the interaction of PTEN with junctional complexes, promoted E-cadherin-dependent cell-cell aggregation, and reverted the Src-induced invasiveness of kidney MDCKts-src cells. In this model, MAGI-1b slightly decreased the activity of AKT, a downstream effector of PI3K. By using dominant-negative and constitutively active AKT expression vectors, we demonstrated that this kinase was included in the pathways involved in Src-induced destabilization of junctional complexes and was necessary and sufficient to trigger invasiveness. We propose that the recruitment of PTEN at adherens junctions by MAGI-1b and the local down-regulation of phosphatidylinositol-3,4,5-trisphosphate pools and downstream effector systems at the site of cell-cell contacts are focal points for restraining both disruption of junctional complexes and induction of tumor cell invasion.