Appearance of blebs on the surface of differentiating Friend erythroleukemia cells

The scanning electron microscope has been employed to examine the surfaces of Friend murine erythroleukemia cells (MEL cells) induced to differentiate in culture with dimethylsulfoxide (DMSO). Whereas immature, undifferentiated cells appear to be relatively smooth with a uniform density of small microvilli, fully differentiated cells are covered with large blebs or lumps having diameters in the range of 0.5-2.0 micrometer. Greater than 85% of induced MEL cells have 'bleby' surfaces after four days of growth in the presence of DMSO when significant hemoglobin synthesis has also taken place. In contrast, only 10% of uninduced MEL cells exhibit surface blebs and hemoglobin synthesis is less than 10% of that observed in induced cells. A control, non-erythroleukemia cell line did not express cell surface blebs in the presence or absence of DMSO. Analysis of three variant MEL cell clones that fail to synthesize hemoglobin in response to DMSO showed that two clones express surface blebs while one does not. This indicates that appearance of cell surface blebs is not functionally or causally linked to hemoglobin synthesis in induced MEL cells.