A fibronectin matrix is required for differentiation of murine erythroleukemia cells into reticulocytes.
Erythroid differentiation of murine erythroleukemia (MEL) cells is far more extensive when the cells are attached to fibronectin-coated dishes than in suspension culture. Cells induced in suspension culture for 4 d become arrested at a late erythroblast stage and do not undergo enucleation. Incubation of cells in suspension beyond 4 d results in lysis. In contrast, cells induced by DMSO on fibronectin-coated dishes for 7 d differentiate into enucleating cells, reticulocytes, and erythrocytes. As determined by quantitative immunoblotting, cells induced in suspension culture accumulate approximately 33% of the amount of the major erythroid membrane protein Band 3 present in erythrocyte, whereas cells induced on fibronectin-coated dishes accumulate 80-100% of the amount present in erythrocytes. Both suspension-induced cells and cells induced on fibronectin-coated dishes accumulate approximately 90% of the amount of spectrin and ankyrin present in erythrocytes. As revealed by immunofluorescence microscopy during enucleation of MEL cells, both Band 3 and ankyrin are sequestered in the cytoplasmic fragment of the emerging reticulocyte. Enucleated and later-stage cells detach from the fibronectin matrix, due to the loss of the surface fibronectin receptor; this mimics the normal release of reticulocytes from the matrix of the bone marrow into the blood. Thus a fibronectin matrix provides a permissive microenvironment within which erythroid precursor cells reside, proliferate, migrate, and express their normal differentiation program.
D001457:Anion Exchange Protein 1, Erythrocyte / Q000502:physiology; D017487:Ankyrins; D001798:Blood Proteins / Q000502:physiology; D002448:Cell Adhesion; D004910:Erythrocyte Membrane / Q000502:physiology; D004920:Erythropoiesis; D005109:Extracellular Matrix / Q000502:physiology*; D005353:Fibronectins / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D004915:Leukemia, Erythroblastic, Acute; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D012156:Reticulocytes / Q000166:cytology*; D013049:Spectrin / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000166:cytology
D001457:Anion Exchange Protein 1, Erythrocyte; D017487:Ankyrins; D001798:Blood Proteins; D005353:Fibronectins; D008565:Membrane Proteins; D013049:Spectrin