Niches Flashcards
What is a stem cell niche?
stem cell niche is the in vivo microenvironment where stem cells both reside and receive stimuli that determine their fate. Therefore the niche should not be considered simply a physical location from stem cells rather as the place where extrinsic signals interact and integrate to influence stem cell behaviour
Is a niche dynamic or static?
stem cell niche is not some quite place where the cells are protected or sth like that. It is more useful to think of the niche as the control tower where the whole operation is taking place
Is the niche protective?
there is some element of protection provided by the niche as they are usually situated in places deep within the organisms (like bones)
How do daughter cells arise in classic developmental biology?
- in classic developmental biology daughter cells that differentiate along distinct lineages arise by one of two mechanisms:
- uneven partition of the cell fate determinants of the mother cell (intracellular signalling)
- orientation of the plane division in which the daughter cells are placed in two different environments leading to differentiation (extracellular signals)
What regulates the balance of differentiation and self renewal?
in reality the balance between self renewal and differentiation is regulated by the balance of extracellular and intracellular signals known today as a stem cell niche
When did the concept of a stem cell niche arise?
stem cell niche concept arose when stem cells such as hematopetic stem cells lost their abilities yo self renew when placed in a different environment
How is the number of stem cells maintained?
if you don’t have space in the niche your daughter cells are pushed out to differentiate → the number of stem cells is limited by the availability of niches
What role does adhesion play in the stem cell niche?
adhesion of stem cells to either the underlying basement membrane or the support cells plays an important role in anchoring stem cells within the niche
What were some hypothesis described by Schoefield 1978?
- stem cells must exist in the association with other cels and those other cells determine the behaviour of the stem cells
- the cells within the tissue prevent the maturation of the stem cell
- if the environment of the progeny of the stem cell is different than the stem cell only after the first generation there will be differences between the stem cell and the progeny
What are the criteria that identify the stem cell niche according to Scadden 2010?
- the niche can exist even in the absence of the stem cells
- niche cells can be abscent and replaced by ECM
- cell-cell and cell-matrix contacts are essential
- blood vessels are always present in the vicinity
- neuronal inputs have increasingly been described
What experiment lead to the the identification of Germ line stem cells?
Lineage tracing by clonal marking analysis has led to the identification of GSCs in both the male and the female germ lines in vivo, within their normal environment
What experiment allows for analysis of specific genes in stem cell maintnance?
Clonal analysis also allows the generation of mutant GSCs in an otherwise wild-type animal, allowing the analysis of a specific gene’s function on stem cell maintenance, self-renewal, and survival.
How do GSCs divide?
both male and female GSCs normally divide with invariant asymmetry, producing precisely one daughter stem cell and one daughter cell that will initiate differentiation.
Describe the cell adhesion significance in the context of drosophila germ cells
In both the ovary and the testis, GSCs are in intimate contact with surrounding support cells that provide critical self- renewal signals, maintenance signals, or both, thereby constituting a stem cell niche. Oriented division of stem cells is important for placing one daughter cell within the niche while displacing the other daughter cell destined to ini- tiate differentiation outside of the germ-line stem cell niche.
What were the first niches described?
the first niches were described in the drosophila gonads
What do the male and female GSCs have in common?
the systems have some things in common - in bothe the stem cells are directly in contact with other cells (cap cells and Hub cells)