title: E-cadherin is important for cell differentiation during osteoclastogenesis.
abstract: E-cadherin, a protein responsible for intercellular adhesion between epithelial cells, is also expressed in the monocyte/macrophage lineage. In this study we have explored the involvement of E-cadherin during receptor activator of nuclear factor-κB ligand (RANKL)-stimulated osteoclast differentiation. Osteoclastogenesis involves a period of precursor expansion followed by multiple fusion events to generate a multinuclear osteoclast that is capable of bone resorption. We asked whether E-cadherin participated in early precursor interactions and recognition or was a component of the osteoclast fusion machinery. Here, we show that endogenous E-cadherin expression is the highest during early stages of osteoclast differentiation, with surface expression visible on small precursor cells (fewer than four nuclei per cell) in both RAW 264.7 cells and primary macrophages. Blocking E-cadherin function with neutralizing antibodies prior to the onset of fusion delayed the expression of TRAP, Cathepsin K, DC-STAMP and NFATc1 and significantly diminished multinucleated osteoclast formation. Conversely, E-cadherin-GFP overexpressing macrophages displayed earlier NFATc1 nuclear translocation along with faster formation of multinucleated osteoclasts compared to control macrophages. Through live imaging we identified that disrupting E-cadherin function prolonged the proliferative phase of the precursor population while concomitantly decreasing the proportion of migrating precursors. The lamellipodium and polarized membrane extensions appeared to be the principal sites of fusion, indicating precursor migration was a critical factor contributing to osteoclast fusion. These findings demonstrate that E-cadherin-mediated cell-cell contacts can modulate osteoclast-specific gene expression and prompt differentiating osteoclast precursors toward migratory and fusion activities.
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario M1C 1A4, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada.
authors.forename: Cara
authors.initials: C
authors.lastname: Fiorino
authors.affiliation: Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario M1C 1A4, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, Ontario M1C 1A4, Canada. Electronic address: harrison@utsc.utoronto.ca.
authors.forename: Rene E
authors.initials: RE
authors.lastname: Harrison
mesh_terms: D000818:Animals; D064200:Cdh1 Proteins / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002459:Cell Fusion; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002465:Cell Movement / Q000187:drug effects; D022081:Cell Surface Extensions / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010012:Osteogenesis / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D053245:RANK Ligand / Q000494:pharmacology; D000067996:RAW 264.7 Cells
chemical_list: D064200:Cdh1 Proteins; C577585:Fzr1 protein, mouse; D053245:RANK Ligand
keywords: Cell–cell interaction; Differentiation; E-cadherin; NFATc1; Osteoclast