Lecture 15 - Stem Cell Basics

Question 1

What is the epiblast?

Answer 1

Stage of embryonic development that gives rise to the germ layers (ectoderm, mesoderm, endoderm).

Begins around the time of implantation into the uterus

Question 2

How do cell differentiation and determination occur?

Answer 2

Epigenetic changes (alterations to chromatin)

Question 3

Determination

Answer 3

Occurs before overt differentiation.

Not morphologically obvious

Question 4

Differentiation

Answer 4

Result of changes in gene expression
Commitment to a cell lineage
Cell changes morphologically so that it can carry out particular function

Question 5

Transdifferentiation

Answer 5

A cell committed to one lineage switches pathways to another lineage.

Question 6

Examples of transdifferentiation

Answer 6

Intestinal metaplasia of the oesophagus.

Squamous metaplasia of the intestinal tract.

Question 7

Can transdifferentiation be induced?

Answer 7

Yes. In cell culture, ectopic expression of master regulator transcription factors

Question 8

Example of transdifferentiation between two closely-related cell types

Answer 8

Pancreatic-lineage cells can transdifferentiate into hepatocytes

Question 9

Intestinal metaplasia

Answer 9

Damage to the oesophageal epithelium through acid reflux leads to conversion of normal squamous epithelium into intestinal epithelium.

Question 10

Danger of intestinal metaplasia of the oesophagus

Answer 10

Is a precursor to oesophageal adenocarcinoma

Question 11

Stem cell that can give rise to several types of mature cell

Answer 11

Multipotent

Question 12

Stem cell that can give rise to any mature cell

Answer 12

Pluripotent

Question 13

Stem cell that can give rise to a new individual, given appropriate support

Answer 13

Totipotent

Question 14

Types of adult tissue
1)
2)
3)

Answer 14

1) Continuously renewing
2) Conditionally renewing
3) Non renewing

Question 15

Example of continuously renewing adult tissues

Answer 15

Bone marrow, skin, gut

Question 16

Examples of conditionally renewing adult tissues

Answer 16

Liver, kidneys (to a lesser extent)

Question 17

Example of a non renewing adult tissue

Answer 17

Cardiac muscle

Question 18

How often is the lining of the GIT replaced?

Answer 18

Once every four days

Question 19

Number of cells lost each day form each person

Answer 19

~20 billion

Question 20

What is a stem cell?

Answer 20

Primitive, undifferentiated cell that can give rise to more specialised cell types or renew itself.

Question 21

Features of stem cells 
1)
2)
3)
4)
5)
6)

Answer 21

1) Capable of self-renewal and differentiation
2) May give rise to transit amplifying cells (compartment-committed cells with a limited division capacity)
3) Often lack specialised organelles, have a high nucleus:cytoplasm ratio
4) Express telomerase (long-lived)
5) Slowly-dividing
6) Few in number

Question 22

How do stem cells normally sit in the body?

Answer 22

Restricted to specific niches

Question 23

Adult-tissue stem cell features
1)
2)

Answer 23

1) Tightly regulated function by powerful transcription factors
2) In an altered environment, tight transcriptional regulation might be relaxed, leading to plasticity.

Question 24

Ways to identify stages of differentiation 
1)
2)
3)
4)

Answer 24

1) Transcription factors
2) Surface molecules (EG: CD)
3) Cytostructural molecules (EG: intermediate filaments)
4) Specific functional gene products

Question 25

Regions of the brain that are stem-cell niches 1) 2)

Answer 25

1) Subventricular | 2) Hippocampal

Question 26

Where do neurons from the subventricular zone end up?

Answer 26

In the olfactory epithelium

Question 27

What might hippocampal neurogenesis have a role in?

Answer 27

Memory

Question 28

Number of cell types in the gut that constantly form from stem cells

Answer 28

Four (goblet, paneth, enteroendocrine, enterocyte)

Question 29

Where in the gut do stem cells sit?

Answer 29

Crypts

Question 30

Paneth cell role

Answer 30

Gut innate immunity. | Produce defensins and lysosome

Question 31

Signalling pathways that regulate crypt stem cell differentiation

Answer 31

Wnt | Notch

Question 32

Where in the hair follicle do stem cells sit?

Answer 32

The bulge

Question 33

Signalling pathways involved in hair follicle stem cell regulation

Answer 33

BMP | Wnt

Question 34

How do stem cells in body niches often behave?

Answer 34

Quiescent stem cells that are not dividing are a tissue reserve that is activated upon damage. Quiescent stem cells give rise to active or progenitor stem cells which are responsible for homeostasis under normal circumstances

Question 35

Type of stem cells in the liver

Answer 35

Facultative stem cells (can conditionally renew)

Question 36

Where are liver stem cells found?

Answer 36

Bipotential stem cells found in the biliary tree

Question 37

How can the liver regenerate?

Answer 37

Either by hepatocyte proliferation or from bipotential stem cells in the biliary tree

Question 38

How can the liver's regenerative ability be impaired?

Answer 38

Cirrhosis, viral infection can lead to scarring,

Question 39

Factors added to fibroblasts to make them become pluripotent stem cells

Answer 39

Yamanaka factors

Question 40

Three sources of stem cells

Answer 40

1) Embryonic 2) iPS 3) Somatic cell nuclear transfer

Question 41

Properties of pluripotent stem cells 1) 2) 3)

Answer 41

1) Grow indefinitely in vitro 2) Capable of colonising all tissues after injection into a blastocyst (chimaeric animal) 3) Maintain normal genetic makeup

Question 42

At which stage do stem cells switch from being totipotent to pluripotent?

Answer 42

At around the 4-8 cell stage

Question 43

``` Signalling systems that control animal development 1) 2) 3) 4) 5) 6) 7) ```

Answer 43

1) Wnt 2) Hedgehog 3) Notch 4) TGFb 5) Tyr kin 6) Nuclear rec 7) Jak/Stat

Question 44

``` Yamanaka factors to induce pluripotency 1) 2) 3) 4) ```

Answer 44

1) Oct-4 2) Sox2 3) Klf4 4) C-myc

Question 45

How are Yamanaka factors introduced to cells?

Answer 45

Viral transfection

Question 46

``` Possible application of iPS in biomedical research 1) 2) 3) 4) ```

Answer 46

1) Basic studies of human development and disorders 2) Functional genomics of human cells 3) Discovery of novel factors controlling tissue regeneration and repair 4) In vitro models for drug discovery, toxicology

Question 47

Particular use for iPS in studying human development

Answer 47

Human brain development is very different to that of other animals iPS can be used to model human cortical development, model developmental diseases such as autism, schizophrenia, epilepsy