Embryonic stem cells from single blastomeres

The fact that deriving embryonic stem (ES) cells from a blastocyst prevents its further development as an embryo is a major issue in human ES cell research. Using eight-cell mouse embryos, we have developed a method of deriving ES cells from a single blastomere, allowing the other seven to continue normal embryonic development. We remove one blastomere and coculture it with green fluorescent protein-labeled ES cells so that it is possible later to separate the clump of blastomere-derived ES cells to a feeder layer for further culturing. The removal of one blastomere is already performed on some human embryos during in vitro fertilization as part of prenatal genetic diagnosis.