L1: Origin of Stem Cells in the embryo Flashcards
What is a stem cell?
Self-renewing cell type in which mitosis produces:
one daughter cell that enters a differentiation pathway;
one that remains in the location of the progenitor cell as a stem cell.
What is a progenitor cell?
Progenitor cells are descendants of stem cells that then further differentiate to create specialized cell types. There are many types of progenitor cells throughout the human body. Each progenitor cell is only capable of differentiating into cells that belong to the same tissue or organ
What causes one daughter cell remain at the location of the progenitor cells as a stem cell?
Asymmetric subcellular distribution of APC (Adenomatous polyposis coli) mRNA
and protein
What does Asymmetric subcellular distribution of APC (Adenomatous polyposis coli) mRNA
and protein result in?
Results in orientation of spindle perpendicular
to basement membrane so that division pushes one daughter cell away while the other remains.
Further daughter differentiates, cell at bm does not. (Scope for further reading!)
What is the role of APC in signalling stem cells?
APC is a negative regulator of Wnt signalling. Therefore, signalling is off in self-renewer, on in differentiating cell.
What is the role of Wnt in stem cells?
Role of Wnt in stem cells is complex and varies with type (eg ESCs and hair follicle stem cells).
What is APC?
The tumor suppressor adenomatous polyposis coli (APC) is a crucial regulator of many stem cell types. In constantly cycling stem cells of fast turnover tissues, APC loss results in the constitutive activation of a Wnt target gene program that massively increases proliferation and leads to malignant transformation.
The activation of the Jak/Stat pathway is very important. When is it activated?
Activated in self-renewing cell by factors from niche (see later) so drives expression of genes important in self-renewal. Is off in the differentiating daughter cell.
What is totipotency?
The ability of a cell to produce any other cell type from its progeny. Zygote and first few generations of blastomeres best known examples.
Pluripotency
The ability of a cell to produce a range of other cell types from its progeny, irrespective of germ layer. Found in embryo and adult.
What is difference between totipotent and pluripotent stem cells?
The difference between totipotent and pluripotent cells is only that totipotent cells can give rise to both the placenta and the embryo. As the embryo grows these pluripotent cells develop into specialized, multipotent stem cells. … There are multipotent stem cells for all of the different types of tissue in the body.
What is the inner cell mass made up of?
Epiblast & Hypoblast
Where are embryonic stem cells derived from?
derived from the epiblast of the blastocyst.
Where are primordial germ cells derived from?
derived from the epiblast but at the border with the hypoblast.
How do stem cell progeny achieve different cell fates?
Concept of Stem Cell Niche: microenvironment that induces factors enabling self-renewal.
Become localised to one side of the cell and present in higher concentrations in one daughter cell → new stem cell.
Why is the position of cell progeny important?
Position of cell important; recruitment of other cells in some cases.
What makes a pluripotent stem cell?
Expression of various transcription factors seems characteristic of pluripotency.
E.g.: (Oct4, Sox2, Klf4, cMyc, Nanog and Lin28)
Why are some ES or EG cells not equal?
Show variation in gene expression patterns, especially Nanog.
What are the other routes to establishment of stem cell characteristics?
RNA-mediated regulation of gene function
Especially long non-coding RNAs that bind DNA as part of a complex.
