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Schliekelman M.J.,Fred Hutchinson Cancer Research Center | Taguchi A.,University of Houston | Zhu J.,Mount Sinai School of Medicine | Dai X.,Mount Sinai School of Medicine | And 19 more authors.
Cancer Research | Year: 2015

Epithelial-to-mesenchymal transition (EMT) is a key process associated with tumor progression and metastasis. To define molecular features associated with EMT states, we undertook an integrative approach combining mRNA, miRNA, DNA methylation, and proteomic profiles of 38 cell populations representative of the genomic heterogeneity in lung adenocarcinoma. The resulting data were integrated with functional profiles consisting of cell invasiveness, adhesion, and motility. A subset of cell lines that were readily defined as epithelial or mesenchymal based on their morphology and E-cadherin and vimentin expression elicited distinctive molecular signatures. Other cell populations displayed intermediate/hybrid states of EMT, with mixed epithelial and mesenchymal characteristics. A dominant proteomic feature of aggressive hybrid cell lines was upregulation of cytoskeletal and actin-binding proteins, a signature shared with mesenchymal cell lines. Cytoskeletal reorganization preceded loss of E-cadherin in epithelial cells in which EMT was induced by TGFb. A set of transcripts corresponding to the mesenchymal protein signature enriched in cytoskeletal proteins was found to be predictive of survival in independent datasets of lung adenocarcinomas. Our findings point to an association between cytoskeletal and actinbinding proteins, a mesenchymal or hybrid EMT phenotype and invasive properties of lung adenocarcinomas. Cancer Res; 75(9); 1789-800. © 2015 AACR.

Li Q.,National University of Singapore | Zhang Y.,National University of Singapore | Pluchon P.,National University of Singapore | Robens J.,National University of Singapore | And 7 more authors.
Nature Cell Biology | Year: 2016

The de novo formation of secretory lumens plays an important role during organogenesis. It involves the establishment of a cellular apical pole and the elongation of luminal cavities. The molecular parameters controlling cell polarization have been heavily scrutinized. In particular, signalling from the extracellular matrix (ECM) proved essential to the proper localization of the apical pole by directed protein transport. However, little is known about the regulation of the shape and the directional development of lumen into tubes. We demonstrate that the spatial scaffolding of cells by ECM can control tube shapes and can direct their elongation. We developed a minimal organ approach comprising of hepatocyte doublets cultured in artificial microniches to precisely control the spatial organization of cellular adhesions in three dimensions. This approach revealed a mechanism by which the spatial repartition of integrin-based adhesion can elicit an anisotropic intercellular mechanical stress guiding the osmotically driven elongation of lumens in the direction of minimal tension. This mechanical guidance accounts for the different morphologies of lumen in various microenvironmental conditions. © 2016 Macmillan Publishers Limited.

Gruber R.,Leibniz Institute for Age Research | Gruber R.,Cancer Research UK Research Institute | Zhou Z.,Leibniz Institute for Age Research | Sukchev M.,Leibniz Institute for Age Research | And 4 more authors.
Nature Cell Biology | Year: 2011

Primary microcephaly 1 is a neurodevelopmental disorder caused by mutations in the MCPH1 gene, whose product MCPH1 (also known as microcephalin and BRIT1) regulates DNA-damage response. Here we show that Mcph1 disruption in mice results in primary microcephaly, mimicking human MCPH1 symptoms, owing to a premature switching of neuroprogenitors from symmetric to asymmetric division. MCPH1-deficiency abrogates the localization of Chk1 to centrosomes, causing premature Cdk1 activation and early mitotic entry, which uncouples mitosis and the centrosome cycle. This misorients the mitotic spindle alignment and shifts the division plane of neuroprogenitors, to bias neurogenic cell fate. Silencing Cdc25b, a centrosome substrate of Chk1, corrects MCPH1-deficiency-induced spindle misalignment and rescues the premature neurogenic production in Mcph1-knockout neocortex. Thus, MCPH1, through its function in the Chk1-Cdc25-Cdk1 pathway to couple the centrosome cycle with mitosis, is required for precise mitotic spindle orientation and thereby regulates the progenitor division mode to maintain brain size. © 2011 Macmillan Publishers Limited. All rights reserved.

Lim J.,Institute of Molecular Cell Biology | Thiery J.P.,Institute of Molecular Cell Biology | Thiery J.P.,National University of Singapore
Development (Cambridge) | Year: 2012

Epithelial-mesenchymal transition (EMT) is a crucial, evolutionarily conserved process that occurs during development and is essential for shaping embryos. Also implicated in cancer, this morphological transition is executed through multiple mechanisms in different contexts, and studies suggest that the molecular programs governing EMT, albeit still enigmatic, are embedded within developmental programs that regulate specification and differentiation. As we review here, knowledge garnered from studies of EMT during gastrulation, neural crest delamination and heart formation have furthered our understanding of tumor progression and metastasis. © 2012. Published by The Company of Biologists Ltd.

Hilgers V.,National University of Singapore | Hilgers V.,European Molecular Biology Laboratory | Hilgers V.,Institute of Molecular Cell Biology | Bushati N.,National University of Singapore | And 3 more authors.
PLoS Biology | Year: 2010

MiR-263a/b are members of a conserved family of microRNAs that are expressed in peripheral sense organs across the animal kingdom. Here we present evidence that miR-263a and miR-263b play a role in protecting Drosophila mechanosensory bristles from apoptosis by down-regulating the pro-apoptotic gene head involution defective. Both microRNAs are expressed in the bristle progenitors, and despite a difference in their seed sequence, they share this key common target. In miR-263a and miR263b deletion mutants, loss of bristles appears to be sporadic, suggesting that the role of the microRNAs may be to ensure robustness of the patterning process by promoting survival of these functionally specified cells. In the context of the retina, this mechanism ensures that the interommatidial bristles are protected during the developmentally programmed wave of cell death that prunes excess cells in order to refine the pattern of the pupal retina. © 2010 Hilgers et al.

Zhang W.,Institute of Molecular Cell Biology | Cohen S.M.,Institute of Molecular Cell Biology | Cohen S.M.,National University of Singapore
Biology Open | Year: 2013

The Hippo pathway has a central role in coordinating tissue growth and apoptosis. Mutations that compromise Hippo pathway activity cause tissue overgrowth and have been causally linked to cancer. In Drosophila, the transcriptional coactivator Yorkie mediates Hippo pathway activity to control the expression of cyclin E and Myc to promote cell proliferation, as well as the expression of bantam miRNA and DIAP1 to inhibit cell death. Here we present evidence that the Hippo pathway acts via Yorkie and p53 to control the expression of the proapoptotic gene reaper. Yorkie further mediates reaper levels posttranscriptionally through regulation of members of the miR-2 microRNA family to prevent apoptosis. These findings provide evidence that the Hippo pathway acts via several distinct routes to limit proliferation-induced apoptosis. © 2013. Published by The Company of Biologists Ltd.

PubMed | Singapore Institute of Medical Biology, National University of Singapore and Institute of Molecular & Cell Biology
Type: Journal Article | Journal: The Biochemical journal | Year: 2016

PAKs (p21 activated kinases) are an important class of Rho effectors. These contain a Cdc42-Rac1 interaction and binding (CRIB) domain and a flanking auto-inhibitory domain (AID) which binds the C-terminal catalytic domain. The group II kinases PAK4 and PAK5 are considered significant therapeutic targets in cancer. Among human cancer cell lines we tested, PAK5 protein levels are much lower than those of PAK4, even in NCI-H446 which has the highest PAK5 mRNA expression. Although these two kinases are evolutionarily and structurally related, it has never been established why PAK4 is inactive whereas PAK5 has high basal activity. The AID of PAK5 is functionally indistinguishable from that of PAK4, pointing to other regions being responsible for higher activity of PAK5. Gel filtration indicates PAK4 is a monomer but PAK5 is dimeric. The central region of PAK5 (residues 109-420) is shown here to promote self-association, and an elevated activity, but has no effect on activation loop Ser(602) phosphorylation. These residues allow PAK5 to form characteristic puncta in cells, and removing sequences involved in oligomerization suppresses kinase activity. Our model suggests PAK5 self-association interferes with AID binding to the catalytic domain, thus maintaining its high activity. Further, our model explains the observation that PAK5 (1-180) inhibits PAK5 invitro.

Matte C.,Institute Armand Frappier and Center for host parasite interactions | Casgrain P.-A.,Institute Armand Frappier and Center for host parasite interactions | Seguin O.,Institute Armand Frappier and Center for host parasite interactions | Moradin N.,Institute Armand Frappier and Center for host parasite interactions | And 3 more authors.
PLoS Pathogens | Year: 2016

The protozoan Leishmania parasitizes macrophages and evades the microbicidal consequences of phagocytosis through the inhibition of phagolysosome biogenesis. In this study, we investigated the impact of this parasite on LC3-associated phagocytosis, a non-canonical autophagic process that enhances phagosome maturation and functions. We show that whereas internalization of L. major promastigotes by macrophages promoted LC3 lipidation, recruitment of LC3 to phagosomes was inhibited through the action of the parasite surface metalloprotease GP63. Reactive oxygen species generated by the NOX2 NADPH oxidase are necessary for LC3-associated phagocytosis. We found that L. major promastigotes prevented, in a GP63-dependent manner, the recruitment of NOX2 to phagosomes through a mechanism that does not involve NOX2 cleavage. Moreover, we found that the SNARE protein VAMP8, which regulates phagosomal assembly of the NADPH oxidase NOX2, was down-modulated by GP63. In the absence of VAMP8, recruitment of LC3 to phagosomes containing GP63-deficient parasites was inhibited, indicating that VAMP8 is involved in the phagosomal recruitment of LC3. These findings reveal a role for VAMP8 in LC3-associated phagocytosis and highlight a novel mechanism exploited by L. major promastigotes to interfere with the host antimicrobial machinery. © 2016 Matte et al.

Sakry D.,Institute of Molecular Cell Biology | Trotter J.,Institute of Molecular Cell Biology
Brain Research | Year: 2015

In the normal mammalian CNS, the NG2 proteoglycan is expressed by oligodendrocyte precursor cells (OPC) but not by any other neural cell-type. NG2 is a type-1 membrane protein, exerting multiple roles in the CNS including intracellular signaling within the OPC, with effects on migration, cytoskeleton interaction and target gene regulation. It has been recently shown that the extracellular region of NG2, in addition to an adhesive function, acts as a soluble ECM component with the capacity to alter defined neuronal network properties. This region of NG2 is thus endowed with neuromodulatory properties. In order to generate biologically active fragments yielding these properties, the sequential cleavage of the NG2 protein by α- and γ-secretases occurs. The basal level of constitutive cleavage is stimulated by neuronal network activity. This processing leads to 4 major NG2 fragments which all have been associated with distinct biological functions. Here we summarize these functions, focusing on recent discoveries and their implications for the CNS. This article is part of a Special Issue entitled SI:NG2-glia(Invited only). © 2015 Elsevier B.V.

News Article | December 15, 2016
Site: www.chromatographytechniques.com

An international research team comprised of six evolutionary biologists sequenced the full genome of a tiger tail seahorse, or Hippocampus comes, for the first time. The world’s oceans are filled with a variety of bizarre and wild organisms, and the seahorse certainly tops the list. For starters, the fish doesn’t physically resemble any other type of fish. The seahorse’s body stands vertical, not horizontal like traditional fish and in lieu of scales or ribs, it has boney plates that act as a shield of defense against predators. Seahorses also lack a pelvic fin, which is essentially the equivalent of not having hind legs. Instead, they navigate through the water by fluttering their unique curled tail up to 30 times per second. And without teeth, the fish uses suction through its tubular mouth to eat. Seahorses are the only known vertebrate to exhibit male pregnancy, as well. Female seahorses are tough to impress, so the males perform an elaborate courting dance, which can last as long as a few days. Once the female is wooed, she transfers more than 1,000 eggs into the male’s pouch through an organ specifically designed for this task. The male fertilizes the eggs and ensures the embryos grow safely in his pouch, just like a mother of any other species would do. When the embryos are ready, the male will begin to feel contractions and actually push the embryos out of the pouch. The babies are on their own from there, and the male wastes no time in starting the process over again. All of these fascinating traits evolved over a very short period of time, further intriguing scientists to learn more. So a team, led by Byrappa Venkatesh of the Institute of Molecular Cell Biology in Singapore, sequenced the full genome of a tiger tail seahorse and published the initial results as the cover story in Nature on Dec. 15. The team chose the tiger tail out of the 47 known species of seahorses because they can be found in abundance near Singapore, where the research was conducted. The researchers already knew that the seahorse lineage diverted from other fish more than 100 million years ago during the Cretaceous period, but by analyzing the fish’s full genome, they can provide answers to questions about the unique traits and mating behaviors that are currently still a mystery, and find out how they are being expressed at the genetic level. One of the initial key discoveries the researchers reported on was that the genome is missing a set of genes responsible for coding enamel, which explains why seahorses don’t have teeth and have to “suck” their food. Another gene loss noted was the lack of tbx4, which regulates growth of pelvic fins and is found in nearly all other vertebrates. The researchers tested the function of this gene by using zebrafish as a model. The team deactivated the tbx4 gene via the CRISPR-cas method and saw that the zebrafish then also lost their pelvic fins, proving the importance of that specific gene in regular pelvic fin development. While the tiger tail seahorse lacks genes crucial to survival for other species, it has six copies of the Pastrisacin gene, which is linked with male pregnancy. According to the researchers, proteins and DNA in seahorses have evolved much faster than their closest cousins, such as pipe fish and sea dragons, but the researchers don’t yet know why. They will be able to get an even better understanding of the peculiarities of the seahorse by comparing the tiger tail genome with other seahorse species, as well as its closest relatives.

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