The second week of development is marked by blastocyst development and the continued implantation process with rapid growth/differentiation of the extraembryonic tissue (trophoblast). The cavity within the blastocyst and the inner cell mass that forms the embryo begin early differentiation. The inner cell mass contains stem cells which can go on to form any tissue/cell within the embryo, they are therefore called pluripotential. In vitro growth of the blastocyst allows isolation of these cells at this stage and their subsequent use in stem cell research.
Week 2 Human blastocyst- the inner cell mass (which will form the entire embryo) and therefore contains stem cells, appears as a dark patch on the left hand side.
A key step in the development of stem cell research has been the identification of cell surface markers (proteins) which identify these cells and their state of undifferentiation.
This page only covers stem cells in relation to Week 2 Blastocyst development. For more complete Stem Cell information see the new notes section Stem Cells.
In order to carry out research on stem cells, it is important to be able to identify them. A number of different research groups in the late 90's generated several antibodies which specifically identified undifferentiated, differentiating or differentiated stem cells from a number of different sources and species. Note that the nomenclature in some cases is based upon the antibody used to identify the cell surface marker.
Stage-Specific Embryonic Antigen-1 (SSEA-1) cell surface embryonic antigen which has a role in cell adhesion, migration and differentiation and is often differentially expressed during development. Can be identified by Davor Solter monoclonal antibody MC-480 (SSEA-1).
Stage-Specific Embryonic Antigen-4 (SSEA-4) cell surface embryonic antigen of human teratocarcinoma stem cells (EC), human embryonic germ cells (EG) and human embryonic stem cells (ES) which is down-regulated following differentiation of human EC cells. Antigen not expressed on undifferentiated murine EC, ES and EG cells but upregulated on differentiation of murine EC and ES cells. Can be identified by Davor Solter monoclonal antibody MC-813-70 (SSEA-4)
Tumor Rejection Antigen (TRA-1-60) Sialylated Keratan Sulfate Proteoglycan expressed on the surface of human teratocarcinoma stem cells (EC), human embryonic germ cells (EG) and human embryonic stem cells (ES).
Tumor Rejection Antigen (TRA-1-81) antigen expressed on the surface of human teratocarcinoma stem cells (EC), human embryonic germ cells (EG) and human embryonic stem cells (ES).
Both TRA antibodies identify a major polypeptide (Mr 240 kDa) and a minor polypeptide (Mr 415 kDa).
Oct-4 (Pou5f1 – Mouse Genome Informatics) gene has an essential role in control of developmental pluripotency (Oct4 knockout embryo blastocysts die at the time of implantation). Oct4 also has a role in maintaining viability of mammalian germline.
Stem Cell Antigen 1 (Sca-1) member of the Ly-6 family of GPI-linked surface proteins (Mr 18 kDa) and a major phenotypic marker for mouse hematopoietic progenitor/stem cell subset.
CD133, AC133, prominin 5 transmembrane glycoprotein (865 aa) expressed on stem cells with hematopoietic and nonhematopoietic differentiation potential.
Alpha 6 integrin
Shamblott M.J. et. al. (1998). PNAS 95: 13726-13731 ; Schuldiner M. et. al. (2000). PNAS 97: 11307 - 11312 ; Thomson J.A. et. al. (1998). Science 282: 1145-1147 ; Reubinoff B.E. et. al. (2000). Nature Biotechnology 18: 399-404 ; Henderson J.K. et. al. (2002). Stem Cells 20: 329-337; Pera M. et. al. (2000). J. Cell Science 113: 5-10.; The Human Embryonal Carcinoma Marker Antigen TRA-1-60 Is a Sialylated Keratan Sulfate Proteoglycan; Oct4 is required for primordial germ cell survival.; Sca-1 expression identifies stem cells in the proximal region of prostatic ducts with high capacity to reconstitute prostatic tissue;
Data based on information from Appendix E.II. NIH Report "Stem Cells: Scientific Progress and Future Research Directions", Chemicon International- Stem cell marker antibodies OMIM and other sources.
INFORMATION FOR HUMAN RESEARCH ETHICS COMMITTEES SHEET NUMBER 5 - STEM CELL RESEARCH The Australian Health Ethics Committee has been approached by human research ethics committees (HRECs) seeking advice on how to review research protocols that involve stem cell research.The following guidance is interim. Formal guidelines will be developed by AHEC in the context of its review of the 1996 NHMRC Ethical guidelines on assisted reproductive technology.