Differential interference microscopy of in vitro-generated enucleated erythrocytes from CD34⁺ cells from normal human bone marrow cells. CD34⁺ cells were cultured under erythroid differentiation conditions and enucleated cells were FACS sorted as described in the Materials and Methods. Morphologically, the erythrocytes ranged from early polylobulated forms with a pinched or puckered membrane, resembling normal reticulocytes (enlarged in inset), to smooth biconcave discocytes.