Stem cells 4 - Differentiation and De-differentiation

Question 1

What is the 3 situations in which cells undergo controlled differentiation?

Answer 1

• stem cell
• regenerating cell
• embryo cell

Question 2

what 2 signals are involved in both limb development and regeneration?

Answer 2

• SHH autocrine signalling
• FGF8

Question 3

explain the difference between gut development and maintenance

Answer 3

• Paneth cells appear 7 days after embryonic gut formation
• CBC-Paneth cell relationship and villus structure differs in embryonic and adult life

Question 4

Explain stem cells in the early embryo

Answer 4

• embryo which has not yet implanted
• pluripotent - make any cell type

Question 5

Explain stem cells in the foetus

Answer 5

• made from partly specialised tissue cells
• multipotent or oligopotent - can make several cell types

Question 6

explain the progressive differentiation steps in embryo development

Answer 6

• totipotent blastomeres
• Intracellular mass
• Epiblast
• ectoderm, mesoderm, endoderm

Question 7

Why do embryos need stem cells?

Answer 7

-

Question 8

explain pre implantation development

Answer 8

• compaction - 8 cell stage
• inner cel lines become inner cell mass
• ICM expresses Nanog (gene involved in pluripotentcy)
• expression is transient (short time)

Question 9

What is the source of embryonic stem cells?

Answer 9

ICM

Question 10

How are ES cells maintained by feeder cells?

Answer 10

• feeder cells are inactivated and do not divide
• secrete LIF which maintains ES cells

Question 11

Which cells secret LIF?

Answer 11

• outer trophoblast cells
• ICM cells have receptors for LIF but can survive without it

Question 12

Why does the embryo not maintain the ICM

Answer 12

• it is not needed unless in diapause where the ICM is able to be maintained for much longer

Question 13

What is the diapause in mice?

Answer 13

• move that have just given birth can ovulate and be fertilised
• held in the uterus without implantation until the female has weaned

Question 14

How do we prove that ES cells are stem cells?

Answer 14

• can be put back into a blastocyst with a different genotype for a trait
• can look at offspring and see which phenotypes are present where (chimeras)
• can be bred to produce offspring only from ES cells
• can produce all cell types

Question 15

Explain how to culture cells to look at dependents of a single cell

Answer 15

• add trypsin to cells on a dish, detaches
• dilute suspension
• add suspension to dish at such a dilution that each cell will be able to make a clonal colony
• single colony picked up
• then replaces

Question 16

What cell types can neural stem cells differentiate into?

Answer 16

• neurons
• glial cells

Question 17

Name 2 applications of ES cells

Answer 17

• cell therapy
• testing new pharmaceutical products on differentiates ES-derived cells