Expanding the Stem Cell Repetoire Flashcards
What are Trophoblast Stem Cells and Extraembryonic Endoderm Stem Cells?
By plating TE or PE cells in specific culture conditions we can expand stem cell lines that grow indefinitely - TS and XEN cells. Both have the capacity to self renew and differentiate into some of the expected cell types
Describe the features of TS cells
Grow indefinitely in culture and when induced to differentiate can form trophoblast giant cells - indicates that they can make some placental trophoblast cells. Upon reintroduction to the embryo, they can contribute to the placenta fully, but mainly in the labytrinthine trophoblast. These cells are suspected to progress to a later stage of development, representing cells in the proliferative zone of the extra embryonic ectoderm (later derivative of TE). Cells captured and grown don’t always correspond to their starting cell type. TS cells can also be directly derived from this proliferative ectodermal extraembryonic compartment of post implantation embryo - shows that TS cells may more accurate represent this stage of development
Describe the features of XEN cells
They’re derived from preimplantation PE. They self renew in culture and differentiate to cells with many properties of later PE derivatives. Injected into the blastocyst, they incorporate into the PE layer. When the embryos are examined later, XEN cells are almost exclusively found in the parietal endoderm. This property is similar to TS cells where they don’t have all the properties of the original cells. There is no analogous embryonic cell for the XEN, unlike TS cells.
What are post-implantation epiblast stem cells?
Stem cells derived from the post implantation epiblast. Have many features in common with the cells they’re derived from, including the ability to make all 3 germ layers - may be considered pluripotent. However, they’re not very good at making germ cells which suggests that they have advanced developmentally beyond that window where epiblast cells can efficiently segregate into the germline - may impact their pluripotent classification
Describe the properties of EpiSCs
They can create all 3 germ layers, not germ cells very well. They’re closest to gastrulation stage epiblast cells. They’re grown in different culture conditions to ES cells and they don’t readily contribute to chimeras upon blastocyst injection. They have primed pluripotency. Mouse EpiSCs grown in same conditions and they share many properties
Describe the concept of primed and naive pluripotency
Naive pluripotency - Suggests that ES cells are more developmentally immature (can readily do germ cells)
Primed pluripotency - Suggests thst EpiSCs are more developmentally advanced
Describe the properties of Human ES cells
Named so because they share many features with mouse ES cells. They can make derivatives of all 3 germ layers however it is unethical to test their contribution to chimeras. Differences include culture conditions, growth properties. These were assumed to be due to the species difference. Seem to have primed pluripotency when it should be naive
Explain the concepts of cell fate and cell potential
Fate is what a cell will do - given its environment etc. Can make cell fate maps by tagging or now more commonly with genetic tricks to label cells.
Potential is what the cell could do - if circumstances were changed
What is meant by specification and determination in terms of stem cell commitment?
Specification - The fate of a cell is specified when it’s capable of differentiating autonomously when placed in a neutral environment (culture dish). At this stage, commitment can be reversed
Determination - Cell is determined when it’s capable of differentiating autonomously even when placed into another region of the embryo. If it will differentiate into a certain cell type despite the location, the commitment is irreversible
