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MM2: Cellular Differentiation + Stem Cells (Stem Cells (stem cell niche =…
MM2: Cellular Differentiation + Stem Cells
fundamental aspects of developmental biology
1) cell division
increases populations
dividing to produce 2 daughter cells
2) cell differentiation
specialisation
enables specific functions
controlled by gene expression
cardiac muscle cells express myosin genes
RBCs express global genes
begins @ blastocyst (2 cell types)...
trophoblast: forms extra embryonic tissues
ICM: pluripotent, forms embryo
in adults: cell repair + normal cell turnover
3) morphogenesis
organising the spatial distribution of cells
Stem Cells
undifferentiated
can differentiate into specialised cells
can self-renew
make more to maintain a pool
asymmetric divison: 1 daughter stem cell remains undifferentiated while the others differentiate
stem cell niche = microenvironment that provides support + signals regulatory self renewal/differentation
poorly understood
direct contact
soluble factors (messengers, cks)
intermediate cells
Where are they?
1) ICM (embryonic stem cells)
2) Foetuses, babies, adults (tissue stem cells)
specifically in eye, brain, skin, breast, gut, bone, marrow, testicles, muscles (probably everywhere but haven't been found yet)
not abundant, rarely divide
3) In lab (induced pluripotent stem cells)
4) in morula (solid ball of 16-32 identical totipotent stem cells)
Stem cell potency = how many types of specialised cells it make differentiate into
1) MULTIPOTENT
can make multiple types, but not all
e.g. tissue stem cells (only make differentiate into cells within the tissue they belong to
haematopoietic stem cells only make blood cells
mesenchymal stem cells can only make osteoblasts, chondrocytes, adipocytes
2) PLURIPOTENT
can make all body cells
e.g. embryonic stem cells
3) TOTIPOTENT
can make all body cells = extra embryonic tissues
e.g. in morula
embryonic stem cells are taken from surplus embryos in fertility clinics with donor consent
grow embryonic stem cells under different conditions (cks, growth factors, serums etc) to create different specialised cells
before a stem cell becomes a specialised cell, it becomes a committed progenitor/transient amplifying cell
divide rapidly to amplify
multipotent
no self-renewal