20. stem cells

connective tissue

extracellular matrix (EMC)

fibers (collagen and elastic)

cells

tissues

distinct combination of cells, their ECM and their products

stem cells

undifferentiated cells

changed their relationship with our bodes depending on where we are in development

stem cell properties

1. degree of potency

2. asymmetrical cell division

3. expression of specific TF and transcriptional regulators

totipotent

can produce all cell types (very early embryo stage)

pluripotent

can produce nearly all cell types (blastocyst stage)

multipotent

can produce only within a single family of types (adult stem cells)

unipotent

one cell type

plant cells

totipotent cells that can dedifferentiate into a stem cell like state

embryonic stem cells

pluripotent that can be differentted into almost any type of cell

hematopoietic cells

multipotent stem cells

can differentiate various type of cells

asymmetric cell division

cellular component will be separated differently

positive feedback loops

commits to the differentiation from stem cells

repress stem cell gene transcription

prevent stem cells from reverting back by repression

Klf4, Oct4, sox2

gene controlled by 3 TF that can reverse cell fate from differentiated to undifferentiated

help reset the epigenetic information 

induced pluripotent stem cells (iPS)

could be used in similar wats to ES cells

iPS are not identical to es cells

all epigenetic information seems not reversed to be identical to ES cells

major sites of adult stem cells

brain, skin, mucles, bone marrow, intestines, testes

skin

epithelia cell in skin constantly regenerating cells attacked to basal lamina can proliferate

intestine/colom

regeneration and differentiation of epithelial cells

bones

hematopoietic stem cells can different various types of hematopoietic cells

brain

neurons stay ing G0 permanently for function

muscle:

upon injury, quiescent muscle stem cells activate to become myoblasts and generate new mucsle tissue

cancer

unregulated proliferation of cells

Wnt

major signal for cell proliferation in intestine

secteted at the bottom of crypts

wnt inactive

not cell proliferation

cells away form crypt no longer receive signal

wnt active

cell proliferation

mutation in APC

unregulated Wnt signaling promotes proliferation of cell that should not divide