The genes for leukemia inhibitory factor and interleukin-6 are expressed in mouse blastocysts prior to the onset of hemopoiesis.

We have investigated the role that hemopoietic regulatory molecules may play in mouse embryogenesis prior to the appearance of hemopoietic stem cells or their microenvironments. Using polymerase chain reaction analysis, we detected mRNA transcripts for interleukin-6 (IL-6) and leukemia inhibitory factor (LIF) but not for granulocyte-macrophage colony-stimulating factor (GM-CSF) or IL-3 in mouse blastocysts at 3.5 days of gestation. Functional IL-6 protein was also detected in cultured blastocysts as a secreted product, as was an activity consistent with the presence of LIF protein. The expression of IL-6 and LIF in blastocysts prior to hemopoiesis suggests that these proteins may regulate the growth and development of trophoblasts or embryonic stem cells.