Stem Cells Flashcards
(32 cards)
four pathways for stem cells
- self renew
- die
- become senescent
- differentiate (mature)
define senescence
stem cell can be metabolically active but not replicate
define symmetric and asymmetric cell division for stem cells
symmetric: may produce two self-renewing stem cells or two daughter cells that will differentiate
asymmetric: produces one self-renewing cell and one committed to differentiation
what is the importance of cell division symmetry/asymmetry?
maintaining cell homeostasis (numbers of overall cells)
name three main types of stem cells
Embryonic Stem Cells (ES Cells)
Induced Pluripotent Stem Cells (iPS cells)
Adult / tissue-specific stem cells
define totipotent
capable of generating ALL cell types that are necessary for embryonic development: entire embryo AND extra-embryonic tissues
define pluripotent t
can produce all cell lineages in entire organism
Are ES and iPS cells totipotent or pluripotent?
pluripotent
cannot produce extra-embryonic tissues but capable of producing all cell lines
where do ES cells come from?
the pluripotent stem cells of the mammalian INNER CELL MASS (ICM)
from inside the blastocyst
how do blastocysts arise? name the key parts
fertilised egg divides multiple times.
ICM surrounded by trophectoderm outer layer
fluid filled cavity
why are ESCs useful for tissue culture?
they can be differentiated to almost any cell type with correct differentiation protocol (correct media which signals to stem cells)
they self-renew indefinitely in culture
what are iPS cells
ADULT cells
manipulated to take on the properties of ES cells
(avoid ethical implications of ESCs)
what are some ways to check that cells are pluripotent?
pluripotent marker genes (extract DNA to find)
multilinear differentiation in vitro
teratoma formation
chimera formation
what is a teratoma?
tumour containing cells of all three germ layers, confirming that cells are potent
how is chimera formation done?
ES cells can be injected back into a developing blastocyst
they incorporate into the ICM
take part in forming a chimeric animal with a mixture of ordinary and ES-derived cells
Define allogenic
cells from a donor that is NOT the patient
can be stored for use in ANY patient
ie. universally usefulde
define autologous
cells from patient modified and reintroduced
immune system rejection often means this is more viable than allogenic cells
how can stem cell renewal be enabled?
by blocking all other pathways (die, senesce, differentiate)
by influencing EXTERNAL SIGNALS, TRANSCRIPTION FACTOR network and chromatin state
what two umbrella factors influence stem cell regulation?
EXTERNAL factors from the stem cell’s microenvironment (stem cell niche)
INTERNAL factors
intrinsic to SC, regulate its response to external cues
Explain mechanisms of external factors influencing stem cell regulation
- physical mechanisms (eg. structural / adhesion factors in ECM)
- biochemical mechanisms (eg. signalling)
what are the three mechanisms of internal factors influencing stem cell relegation?
cytoplasmic determinants
transcriptional regulation
epigenetic regulation
how do cytoplasmic determinants (internal factor) influence stem cell regulation?
stem cell division can be asymmetric because a cell fate determinant is localised to one side of the cell –> allocated to one of the daughter cells upon division
define transcriptional factors and what their purpose is
proteins that REGULATE GENE EXPRESSION by controlling the rate at which DNA is transcribed to RNA
process is crucial for differentiation / response to environmental stimuli
how do transcriptional factors affect SC regulation?
specific transcription factors in embryonic stem cells maintain pluripotency: “ES-critical genes”
