Stem Cells & Differentiation

Question 1

Differentiation (unspecialized to specialized)

Answer 1

Occurs in

1. Embryo - embryonic development
2. After birth- growth
3. Adulthood - maintenance

Question 2

Differentiation

Answer 2

Distinct ID differential gene expression (morphology & phenotype) also involved in differential gene expression

Question 3

Differentiation can be triggered by __________

Answer 3

Extracellular signals (inducer to responder)

Question 4

Fully differentiated

Answer 4

1. Terminally differentiated, stop dividing & stable state (have major structural change)
2. Blood stem cells - red blood cells lose nucleus & become hemoglobin, white blood cells have multibody nucleus & are granules

Question 5

Genes for differentiation

Answer 5

RTFs master regulators that are necessary & sufficient for differentiation

Question 6

MyoD

Answer 6

1. RTF muscle differentiation
2. Mutate- no muscle (necessary)
3. Ectopic expression-muscle (sufficient)

Question 7

Muscle differentiation

Answer 7

1. somites → myoblasts → muscle (Pax3+ + Pax7+ committed, but not differentiated)
2. myoblasts divide & stop dividing
3. Differentiation make muscle proteins & structural changes (fuse → myotubes → muscle fibers)

Question 8

Muscle stem cells

Answer 8

Satellite cells (injury → activation → regeneration)

Question 9

Blood differentiation

Answer 9

Hematopoietic stem cells (HSCs) where its niche is bone marrow, stem cell hallmarks have self-renewal & multipotent

Question 10

Stem cells

Answer 10

Self-renewal asymmetric division

Question 11

Skin differentiation

Answer 11

epidermis outer, harsh environ. regenerate (stem cells niche)

Question 12

Gut differentiation

Answer 12

Gut lining, harsh environ.

regenerate every 4 days (stem cell niche)

Question 13

Adult stem cells (ASCs) (need niche)

Answer 13

1. multipotent (limited)
2. HSCs (blood)
3. satellite cells (muscle)
4. gut stem cells (gut)

Question 14

Embryonic stem cells (ESCs)(don’t need niche)

Answer 14

1. pluripotent (not limited)
2. Make all 3 germ layer
3. Inner Cell Mass of blastocyst (ICM)

Question 15

Mouse ESCs

Answer 15

1. Self-renewal in vitro
2. Indefinity (no niche)
3. Pluripotent- inject into blastocyst make all 3 germ layers

Question 16

ESCs can lead to ________

Answer 16

Disease cells

Question 17

Maintaining mouse ESCs

Answer 17

1. LIF + BMP
2. Increase Oct 3/4, Sox2, Esrrb, Kfl4 (RTFs)
3. Decrease differentiation

Question 18

Mouse epiSCs (5 days old)

Answer 18

1. Epiblast stem cells (not ESCs)
2. Pluripotent in vitro like ESCs
3. Can’t form chimera in new animals in vivo unlike ESCs

Question 19

Human ESCs (not ethical)

Answer 19

1. Same RTFs as mouse ESCs
2. Maintain stemness in culture
3. FGF + Nodal (unlike mouse ESCs)
4. BMP → differentiation (unlike mouse ESCs)

Question 20

Human ESCs is similar to ________

Answer 20

Mouse epiSCs

Question 21

Plasticity of differentiated cells

Answer 21

1. Can dedifferentiate
2. Lose differentiated characteristics become “stem cell”
   go backwards (divide)
3. can transdifferentiate no dedifferentiation to diff. cell type
4. Test by cloning if a mature nucleus can support embryonic development

Question 22

Cloning (frogs)

Answer 22

1. Somatic cell nuclear transfer (SCNT), somatic nucleus can support embryonic development
2. Adult nucleus are old & decrease efficiency & tadpole nucleus is young increase efficiency

Question 23

Cloning experiment (frogs)

Answer 23

1. Adult nucleus ↓ efficiency
2. Tadpole nucleus ↑ efficiency
3. Blastocyst nucleus ↑↑ efficiency

Question 24

Genomic equivalence (Frogs)

Answer 24

1. Adult nucleus similar to embryonic nucleus

2. No permanent changes to DNA

Question 25

Cloning in mammals (mouse or sheep like dolly)

Answer 25

1. Most die before birth, if survive they became sick 2. Low efficiency, where it had incomplete reprogramming of nucleus, reverse epigenetic changes, DNA methylation, & histone modification 3. Improper expression (5% of total genes & 50% of imprinted genes)

Question 26

Cloning in humans

Answer 26

1. Therapeutic cloning to blastocyst stage (not implanted) | 2. Isolate ESCs for research

Question 27

Cloning in human have a ________

Answer 27

14-day rule (individualization)- starts gastrulation & stops twinning or fusion

Question 28

Reproductive cloning

Answer 28

Cloned embryo which led to a cloned uterus which led to a cloned baby (banned)

Question 29

Therapeutic cloning

Answer 29

Cloning by SCNT, cloned embryo matches the patient, human beings can still give twins (no gastrulation) but it also destroys blastocyst

Question 30

Is IVF ethical?

Answer 30

Extra embryos (frozen, donated, discarded)

Question 31

Reprogramming by cell fusion

Answer 31

1. Fuse 2 cells (common in cytoplasm, tetraploid)

Question 32

Chick blood cell

Answer 32

1. No transcription 2. Fuse with human cell, chick blood cell starts transcription 3. Human cell reprogramed chick cell (shows conservation)

Question 33

Human liver cells

Answer 33

``` 1. Fuse with mouse muscle human cell (expresses muscle genes) ```

Question 34

_________ factors can reprogram

Answer 34

Cytoplasmic

Question 35

Transdifferentiation

Answer 35

1. Reversible stability, change gene expression 2. C. elegans- epithelium → neuron 3. Common in regeneration

Question 36

Regenerative medicine

Answer 36

1. Organ donation- shortage for 3-5 years & rejection from immunosuppressive drugs

Question 37

Pros & Cons of ESCs

Answer 37

1. Pro: pluripotent | 2. Con: Too potent tumor risk & may face rejection if not your own cells

Question 38

Pro & Cons of ASCs

Answer 38

1. Pro: no rejection if from self | 2. Con: not pluripotent

Question 39

iPSCs (induced pluripotent stem cells)

Answer 39

Skin cells + 4 genes → iPSCs, where the 4 genes are the different RTF (Oct 4, Sox2, Kfla4, c- Myc) & also iPSCs is equivalent to ESCs where they are self-renewal & pluripotent (chimera)

Question 40

Clinical trials with iPSCs

Answer 40

1. Macular degeneration 2. Skin cells → iPSCs → eye cells (Injected into patients found not an immune match, had safe slight improvements & the injected cells led to mutations)

Question 41

Clinical trials with iPSCs (recently)

Answer 41

Patient → iPSCs → eye cells → inject immune match (They started with the eyes because easy access not vital, easy readout, & 2 eye)

Question 42

Skin cells → iPSCs → heart cells

Answer 42

Spontaneously assemble beating in a dish

Question 43

Organoids

Answer 43

Could make things like mini brains or mini kidneys

Question 44

Blastoids

Answer 44

Artificial “embryo”( Implanted, no live embryo, but has placental cells)