Oct-4: lessons of totipotency from embryonic stem cells.

The Oct-4 transcription factor is expressed in embryonic stem cells and germ cells of the mouse embryo. Cells that are driven into embryonic and extraembryonic somatic differentiation lose Oct-4 expression. Oct-4 is crucial for the maintenance of the totipotency of embryonic cells at early developmental stages as demonstrated recently by homologous recombination. Since during embryogenesis Oct-4 is restricted to germ cells, it is possible that it plays a key role for the germline lineage by preventing differentiation of these cells during gastrulation. Thus, Oct-4 appears to be a key regulator of totipotency during the life cycle of mammals. Copyright 1999 S. Karger AG, Basel