Embryonic stem cells: a signalling perspective

Since their discovery more than 30 years ago, embryonic stem (ES) cells have been propelled from relative obscurity into the centre stage of international attention. They have enabled the study of gene function in animal models, provided a platform for the study of early developmental processes and now their enormous promise for the study and treatment of many diseases is being tested, although to date very few clinical studies have been initiated to translate this promise into therapeutic outcome. Here, I review the progress made in understanding how signals from the environment influence pluripotent cell self-renewal and differentiation and discuss some of the differences encountered between pluripotent cells from various species and distinct developmental origins. The interaction between these signal transduction pathways is of critical importance, as it ultimately orchestrates the behaviour of ES cells by controlling the expression of pluripotency determinants as well as lineage effectors. Induced pluripotent stem cells (iPS cells) generated by reprogramming of somatic cells are also discussed and related to the pluripotent cell states which can be captured during normal embryonic development.