Cell fate during development is defined by transcription factors that act as molecular switches to activate or repress specific gene expression programmes. The POU transcription factor Oct-3/4 (encoded by Pou5f1) is a candidate regulator in pluripotent and germline cells and is essential for the initial formation of a pluripotent founder cell population in the mammalian embryo. Here we use conditional expression and repression in embryonic stem (ES) cells to determine requirements for Oct-3/4 in the maintenance of developmental potency. Although transcriptional determination has usually been considered as a binary on-off control system, we found that the precise level of Oct-3/4 governs three distinct fates of ES cells. A less than twofold increase in expression causes differentiation into primitive endoderm and mesoderm. In contrast, repression of Oct-3/4 induces loss of pluripotency and dedifferentiation to trophectoderm. Thus a critical amount of Oct-3/4 is required to sustain stem-cell self-renewal, and up- or downregulation induce divergent developmental programmes. Our findings establish a role for Oct-3/4 as a master regulator of pluripotency that controls lineage commitment and illustrate the sophistication of critical transcriptional regulators and the consequent importance of quantitative analyses.

Quantitative expression of Oct-3/4 defines differentiation, dedifferentiation or self-renewal of ES cells.

http://web.mit.edu/7.31/restricted/pdfs/F05_and_earlier/Nichols.pdf

Formation of Pluripotent Stem Cells in the Mammalian Embryo Depends on the POU Transcription Factor Oct4

https://www.cell.com/cell/pdf/S0092-8674(01)00622-5.pdf

The Novel Zinc Finger-Containing Transcription Factor Osterix Is Required for Osteoblast Differentiation and Bone Formation

Targeted gene disruption in the mouse shows that the Sonic hedgehog (Shh) gene plays a critical role in patterning of vertebrate embryonic tissues, including the brain and spinal cord, the axial skeleton and the limbs. Early defects are observed in the establishment or maintenance of midline structures, such as the notochord and the floorplate, and later defects include absence of distal limb structures, cyclopia, absence of ventral cell types within the neural tube, and absence of the spinal column and most of the ribs. Defects in all tissues extend beyond the normal sites of Shh transcription, confirming the proposed role of Shh proteins as an extracellular signal required for the tissue-organizing properties of several vertebrate patterning centres.

Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function.

We describe the derivation of pluripotent embryonic stem (ES) cells from human blastocysts. Two diploid ES cell lines have been cultivated in vitro for extended periods while maintaining expression of markers characteristic of pluripotent primate cells. Human ES cells express the transcription factor Oct-4, essential for development of pluripotential cells in the mouse. When grafted into SCID mice, both lines give rise to teratomas containing derivatives of all three embryonic germ layers. Both cell lines differentiate in vitro into extraembryonic and somatic cell lineages. Neural progenitor cells may be isolated from differentiating ES cell cultures and induced to form mature neurons. Embryonic stem cells provide a model to study early human embryology, an investigational tool for discovery of novel growth factors and medicines, and a potential source of cells for use in transplantation therapy.

Embryonic stem cell lines from human blastocysts: somatic differentiation in vitro.

https://www.cell.com/cell/pdf/S0092-8674(00)80259-7.pdf

Cbfa1, a Candidate Gene for Cleidocranial Dysplasia Syndrome, Is Essential for Osteoblast Differentiation and Bone Development

Embryo A Laboratory Manual, Second Edition By Brigid Hogan, Vanderbilt University Medical School; Rosa Beddington, National Institute for Medical Research, London; Frank Costantini, Columbia University; Elizabeth Lacy, Memorial Sloan-Kettering Cancer Center The 1986 publication of Manipulating the Mouse Embryo catalyzed the interaction between molecular biology and mammalian embryology. For the first time, detailed instructions on how to begin applying recombinant DNA technology to important questions about mammalian embryonic development were made available to a broad audience. The gathering pace of such studies in recent years has brought improvements to existing methods and fueled the creation of new and powerful technologies. The second edition of this classic manual has been completely revised and expanded to incorporate these advances. It contains new sections on the production and analysis of transgenic mice, the manipulation of preimplantation embryos to generate chimeras, the culture and manipulation of embryonic stem cells, including gene "knockouts," and techniques for visualizing genes, gene products, and specific cell types. As before, included with the protocols is a summary of current understanding of mouse development at a molecular level. In its new edition, this manual of proven distinction is again an authoritative and comprehensive source of technical guidance for experienced investigators and an essential resource for newcomers to mammalian genetics and embryology.

Manipulating the Mouse Embryo

Axis Development and Early Asymmetry in Mammals

Embryonic stem cells (ES) cells were injected into host blastocysts either in groups of 10–15 cells or as single cells in order to test their developmental potential in the developing embryo. The analysis of midgestation chimaeras, by electrophoretic separation of glucose phosphate isomerase (GPI) isozymes, showed that ES cells were capable of colonizing trophectoderm and primitive endoderm derivatives at a low frequency, as well as producing a high rate of chimaerism in tissues of the fetus and extraembryonic mesoderm.

Rosa S.P Beddington

Papers

Cbfa1, a Candidate Gene for Cleidocranial Dysplasia Syndrome, Is Essential for Osteoblast Differentiation and Bone Development

Manipulating the Mouse Embryo

Axis Development and Early Asymmetry in Mammals

An assessment of the developmental potential of embryonic stem cells in the midgestation mouse embryo.

Anterior primitive endoderm may be responsible for patterning the anterior neural plate in the mouse embryo