Monolayer culture conditions suitable for primitive erythroid cell differentiation from embryonic stem cells in vitro

Embryonic stem (ES) cells effectively differentiated into primitive erythroid/mesodermal cells when grown in the absence of both a feeder layer and leukemia inhibitory factor (LIF). The formation of a three-dimensional structure, exogenous mesoderm induction factors and exogenous hematopoietic growth factors were not essential for their differentiation. Primitive erythroid cells were first detected on day 5 in the differentiation-permissive cultures. Differentiation into other mesodermal cells was always preceded by that into primitive erythroid cells. Precursor cells of erythroid cells but of other hematoid cells were also detected in this system. This model system is useful for studying the early steps of mesoderm formation in mouse embryogenesis.