Stem Cells

Stem Cell

1. Not terminally differentiated

2. Capable of unlimited division

3. Self renewing

Progenitor Cells

1. Divide a limited number of times

2. On a path to terminal differentiation

3. Not self renewing

Totipotent

Give rise to every cell of the body (embryonic)

Pluripotent

Give rise to cells in all 3 germ layers (placental)

Multipotent

Can become a subset of cells in the organism (organ)

Unipotent

Contributes to 1 cell type of the tissue (organ)

Terminally differentiated (not stem cell)

Divides a limited amount of time but does not change cell type

Stages of development in animals

1. zygote

2. blastula

3. gastrula

4. segmented embryo

5. larva

6. adult

Stem Cell Niche

Place often with unique adhesion (ECM or cell-cell) and work together

Niche

Distal tip expresses a delta ortholog lag-2

Cells under a distal tip express the notch receptor ortholog glp-2 and are senstive to notch signaling

cells divide in distal, pushing some cells out of niche

Once pushed out of niche, notch is no longer present and cells undergo meiosis to make oocytes

Normal Notch

• Lots of small dividing nuclei around DTC

• Cells properly develop into sperm and oocytes

Constitutatively active notch

• Germline is full of cells that never enter oogenesis

• Sterile

• Develop germline tumors

Loss of function notch

• Germline has few cells and lost stem cell niche

• Sterile

• Few germ cells are produced

• Same phenotype as laser ablating DTC

Nuclear Transfer

1. Remove the nuclei for a verified stem cell.

2. Collect the Nuclei from a terminally differentiated cell.

3. Place the Nuclei into the stem cell.

The newly derived hybrid cell is Pluripotent like the original stem cell There is large-scale remodeling of the chromatin Chromatin decondenses (nuclei grows 50x) X-inactivation is reversed

iPSCs

A set of mRNAs that enrich stem cells yet did not confer stemness except for Oct4, Sox2, Klf4, Myc) and can revert to pluripotent stemcells and reduce the need for embryonic stem cells

What happens when stem cells lose niche

Develop a teratoma and be in any tissue

Organoids

An intermediate that depletes stem cell population that is artificially grown and have less function than the natural counterpart

Liver

• detoxification

• metabolism - glucose<->glycogen, non-essential amino acids

• synthesis of lipoproteins, cholesterol, and plasma serum proteins

• digestive functions

• biotransformation

• storage of glycogen

• largest organ

• endoderm that shares progenitors with stomach, intestine, colon, and pancreas

Liver regeneration

• Adjusts to organism size large or smal;

• Signalling molecules (EGF, HGF, etc.) and physical environmental cues

• Insulin and bile acids

Homeostasis

the state of steady internal physical and chemical conditions

maintained by living systems.

Intestines and gastrointestinal tract

Absorb nutrients and secretes waste, acidic, proteases, environmental toxins, and lots of movement with a turnover of 3-5 days

Small intestine

single layered epithelium

• absorptive cells

• mucus secreting cells

• enteroendocrine cells

• paneth cells

Cre Recominase

• Cre-mediated excision of regions between LoxP sites.

• Permanent and inherited by all later generations of cells and mice.

• LacZ(β-galactosidase) turns the clear X-gal substrate Blue

Using promoters

Lgr5- promoter expresses in a wide range of stem cells

ROSA26 is expressed in nearly every cell type.

What controls Wnt?

Signals from surrounding tissue:

BMP4 inhibits Wnt

But: Wnt and Hh activate Bmp4

What controls migration?

Ephrin (ligand) and Eph (receptor) control of cell motility and the loss of migration control leads to disrupted villus structure

Notch

controls the balance in numbers of secretory cells (inactive notch) and absorptive cells.

Positive Selection

Select the presence of something

Negative Selection

You select against the presence of something