Chapter 5: Stem Cells Flashcards
3 Methods that stem cells can divide
1) symmetrical
2) single stem cell asymmetry
3) Population asymmetry
symmetrical cell division
stem cell divides into eitehr 2 self renewing stem cells, or 2 daughte rcells that are committed to differentiate
results in expansion or reduction of SC population
single stem cell asymmetry
stabilization of SC pop becaue one division results in 1SC and 1 daughter cell taht can differentiate
population asymmetry
some SC in the population are more prone to produce differentiated progeny, while other SCs in the population divide symmetrically to maintain the stem cell pool.
What stages will an embryo be totipotent
zygote up to 8 cell stages. These calls can produce all CELLS. Totipotent cells can make both germ layers and extraembryonic cells.
Plouripotent cells
capable of producing of a single lineage. Can be either embryonic stem cells or stem cells for extraembryonic structures.
is a zygote pluri or totipotent
pluripotent
T/F: Pluripotent cells can undergo infinite generations of self renewal
true .
T/F Multipotent cells can undergo infinite generations of self renewal
false. There is a finite number of generatinos for self renewal. contributes to aging.
____ SCS generate cells for that particular tissue type in which they reside
multipotent stem cells.
2 fates of a multipotent stem cell
MP cells can either repliicate into another MP, or the original MP can mature into progenitor cells without needing to produce progenitory daughter cells.
progenitor cells are aka
transit amplifying cels.
T/F Progenitor cells are capable of unlimited self renewal
false. they only divide a few times before differentiating. cells of the progenitor pool can mature into different but related cell types.
Precursor cell
formed by a progenitor cell of a particular lineage. Basically an immature already-differentiated cell: ex/ a UNIPOTENT stem cell: a precursor that generates only on cell type (ex/ spermatogonia).
T/F Precursor cells are unipotent
true. They are still “potent” because they can divide and differentiate–even though they only mature into one specific cell type at that point.
T/F: terminally differentiated cells are unipotent
false. they are not potent at all anymore because they are not mitotically active. Ex/ sperm do not divide by mitosis, but the spermatogonia precursors do.
stem cell niche
the microenvironment that surrounds a stem cell. extracellular/environmental mechanisms lead to intracellular changes that regulate stem cell behaviour.
5 methods of stem cell regulation
1) physical mechanisms: structural and adhesion factors in the ECM, causes differences in cell to cell or cell to matrix interactions. Subsequent cell density can alter mechanical forces, influencing stem cell beahviour.
2) chemical regulation: secreted proteins from neighboring cells can influence SC states.
- endocrine, paracrine, and juxtacrine mechanisms (ex/ tgfbeta paracrine factor stimulates ECM formation/collagen production, which later acts as a physical mechanism for stem cell regulation).
3) cytoplasmic regulation: as a SC divides, factors determining cell fate are either selectively partitioned to one daughter cell towards a specific fate. (ie/ asymmetric spreading of intracellular factors cause daughter cells to differentiate differently)
- asymmetric localization of cytoplasmic determinant.
4) transcriptional regulation: occurs through TF network to keep SCs in a quiescent state, not actively dividing, or active proliferative state. TFs can direct daughter cells towards a specific fate.
5) epigenetic regulation: chromatin will be different states of accesibility ( uncoiled vs highly coiled), acting to regulate gene expression that impacts stem cell behaviour and division.
