title: α6β1- and αV-integrins are required for long-term self-renewal of murine embryonic stem cells in the absence of LIF.
abstract: BACKGROUND
  The growth properties and self-renewal capacity of embryonic stem (ES) cells are regulated by their immediate microenvironment such as the extracellular matrix (ECM). Integrins, a central family of cellular ECM receptors, have been implicated in these processes but their specific role in ES cell self-renewal remains unclear.
  
  
  RESULTS
  Here we have studied the effects of different ECM substrates and integrins in mouse ES cells in the absence of Leukemia Inhibitory Factor (LIF) using short-term assays as well as long-term cultures. Removal of LIF from ES cell culture medium induced morphological differentiation of ES cells into polarized epistem cell-like cells. These cells maintained epithelial morphology and expression of key stemness markers for at least 10 passages in the absence of LIF when cultured on laminin, fibronectin or collagen IV substrates. The specific functional roles of α6-, αV- and β1-integrin subunits were dissected using stable lentivirus-mediated RNAi methodology. β1-integrins were required for ES cell survival in long-term cultures and for the maintenance of stem cell marker expression. Inhibition of α6-integrin expression compromised self-renewal on collagen while αV-integrins were required for robust ES cell adhesion on laminin. Analysis of the stemness marker expression revealed subtle differences between α6- and αV-depleted ES cells but the expression of both was required for optimal self-renewal in long-term ES cell cultures.
  
  
  CONCLUSIONS
  In the absence of LIF, long-term ES cell cultures adapt an epistem cell-like epithelial phenotype and retain the expression of multiple stem cell markers. Long-term maintenance of such self-renewing cultures depends on the expression of β1-, α6- and αV-integrins.
authors.affiliation: Biocenter Oulu, Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 5, Oulu, 90220, Finland. sandhanakrishnan.cattavarayane@oulu.fi.
authors.forename: Sandhanakrishnan
authors.initials: S
authors.lastname: Cattavarayane
authors.affiliation: Biocenter Oulu, Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 5, Oulu, 90220, Finland. rpalovuo@gmail.com.
authors.forename: Riitta
authors.initials: R
authors.lastname: Palovuori
authors.affiliation: Biocenter Oulu, Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 5, Oulu, 90220, Finland. kishoredrtr@gmail.com.|Current address: Université de Lorraine, CS 25233, Nancy, cedex, 54052, France. kishoredrtr@gmail.com.
authors.forename: Jayendrakishore
authors.initials: J
authors.lastname: Tanjore Ramanathan
authors.affiliation: Biocenter Oulu, Oulu Center for Cell-Matrix Research, Faculty of Biochemistry and Molecular Medicine, University of Oulu, Aapistie 5, Oulu, 90220, Finland. aki.manninen@oulu.fi.
authors.forename: Aki
authors.initials: A
authors.lastname: Manninen
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D003094:Collagen / Q000737:chemistry; D053595:Embryonic Stem Cells / Q000166:cytology / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D039121:Integrin alpha6beta1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D039564:Integrin alphaV / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007797:Laminin / Q000737:chemistry; D053605:Leukemia Inhibitory Factor / Q000172:deficiency; D051379:Mice; D008856:Microscopy, Fluorescence; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D039121:Integrin alpha6beta1; D039564:Integrin alphaV; D007797:Laminin; D053605:Leukemia Inhibitory Factor; D034741:RNA, Small Interfering; D014157:Transcription Factors; D003094:Collagen