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Targeted gene deletion demonstrates that the cell adhesion molecule ICAM-4 is critical for erythroblastic island formation.

Erythroid progenitors differentiate in erythroblastic islands, bone marrow niches composed of erythroblasts surrounding a central macrophage. Evidence suggests that within islands adhesive interactions regulate erythropoiesis and apoptosis. We are exploring whether erythroid intercellular adhesion molecule 4 (ICAM-4), an immunoglobulin superfamily member, participates in island formation. Earlier, we identified alpha(V) integrins as ICAM-4 counterreceptors. Because macrophages express alpha(V), ICAM-4 potentially mediates island attachments. To test this, we generated ICAM-4 knock-out mice and developed quantitative, live cell techniques for harvesting intact islands and for re-forming islands in vitro. We observed a 47% decrease in islands reconstituted from ICAM-4 null marrow compared to wild-type marrow. We also found a striking decrease in islands formed in vivo in knock-out mice. Further, peptides that block ICAM-4/alpha(V) adhesion produced a 53% to 57% decrease in reconstituted islands, strongly suggesting that ICAM-4 binding to macrophage alpha(V) functions in island integrity. Importantly, we documented that alpha(V) integrin is expressed in macrophages isolated from erythroblastic islands. Collectively, these data provide convincing evidence that ICAM-4 is critical in erythroblastic island formation via ICAM-4/alpha(V) adhesion and also demonstrate that the novel experimental strategies we developed will be valuable in exploring molecular mechanisms of erythroblastic island formation and their functional role in regulating erythropoiesis.

Pubmed ID: 16690966


  • Lee G
  • Lo A
  • Short SA
  • Mankelow TJ
  • Spring F
  • Parsons SF
  • Yazdanbakhsh K
  • Mohandas N
  • Anstee DJ
  • Chasis JA



Publication Data

September 15, 2006

Associated Grants

  • Agency: NIDDK NIH HHS, Id: DK 32094
  • Agency: NIDDK NIH HHS, Id: DK 56267

Mesh Terms

  • Animals
  • Base Sequence
  • Bone Marrow Cells
  • Cell Adhesion Molecules
  • DNA
  • Erythroblasts
  • Erythroid Precursor Cells
  • Erythropoiesis
  • Gene Targeting
  • Integrin alphaV
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Models, Molecular
  • Protein Structure, Tertiary