Lecture 20: Controlling proliferation and differentiation

Question 1

What is erythropoietin?

Answer 1

Secreted cytokine that stimulates red blood cell production

Question 2

What are mitogens as an external factor?

Answer 2

Stimulate proliferation by driving the cell cycle

Question 3

What are growth factors as an external factor?

Answer 3

Stimulate growth

Question 4

What are survival factors as an external factor?

Answer 4

Suppress apoptosis

Question 5

What are differentiation factors as an external factor?

Answer 5

Control cell lineage

Question 6

What is marked by R in the cell cycle?

Answer 6

The restriction point Cells no longer need mitogens Handover from Cdk4/6 to Cdk2 driven by rise of Cyclin E

Question 7

What is the overall process of mitogens triggering cell cycle entry?

Answer 7

1. Mitogens bind bind to receptors and activate RAS-MAPK signalling pathways and turn on transcription factors
2. 2. Expression of cyclin D gene and Cyclin D protein activates Cdk4/6
3. The complex phosphorylates Rb to let go of E2F
4. E2F drives Cyclin E expression which activates Cdk2
5. Positive feedback where cdk2-cyclin E phosphorylates Rb and Cyclin E increases
6. Drives entry into S phase

Question 8

What is the process of proliferation restriction?

Answer 8

Restricted in the base of the crypt 1. Paneth cells secrete Wnt signals 2. Stem cells induce cyclin D and proliferate 3. Precursor cells migrate out of crypt away from Wnt signals 4. When out of range they stop proliferating and differentiate