Gut Signalling

Question 1

What is the frequency of Wnt pathway mutations in colorectal cancer?

Answer 1

Inherited caused by 15% - familial APC mutations induce loss of function.

Sporadic caused by 85% - 85% APC
10% B catenin.

Question 2

How do ephrins signal the boundary between crypts and villi?

Answer 2

proliferative and paneth cells in crypts produced EphB (RTK)
Differentiated cells express Ephrins.

At boundary ephrins bind EphB preventing cells moving up.

Question 3

What are the different types of cadherins?

Answer 3

E is epithelial
N is mesenchymal
P is stratified epithelial
Ve is endothelial.

Question 4

Which GEF is used in the Ras pathway?

Answer 4

Sos, activated by binding SH3 domains of Grb2.

Question 5

How is wnt signalling preventing in the villus?

Answer 5

BMP proteins from villus core inhibit expression of Hedgehog and Wnt.

Question 6

How do mutations affect Ras in cancer?

Answer 6

They prevent GTP hydrolysis.