DEVELOPMENTAL EXPRESSION OF MYELOID-LEUKEMIA INHIBITORY FACTOR GENE IN PREIMPLANTATION BLASTOCYSTS AND IN EXTRAEMBRYONIC TISSUE OF MOUSE EMBRYOS

Murine leukemia inhibitory factor (LIF) protein is a growth factor which has the ability to maintain the developmental potential of pluripotent embryonic stem cells through a specific receptor. We have examined the expression pattern of the LIF gene from the preimplantation state (3.5 days post coitum) to the midgestation stage (12.5 days post coitum) of the mouse embryo. LIF transcripts were detected at the preimplantation blastocyst stage, whereas no transcripts were detectable in embryonic stem cells. LIF gene transcription continued in the extraembryonic tissue of the 7.5-day and in the placenta of 9.5-, 10.5-, and 12.5-day post coitum embryos. No transcripts were detected in the embryo proper of the corresponding stages. Our results suggest that this growth factor is synthesized in the extraembryonic part of the embryo and acts on the embryonic tissues during early mouse development.