Wnt signalling

Question 1

What is the Hg, Wg and En autoregulatory loop?

Answer 1

Wg and Hh maintain each others expression in an autoregulatory loop
Hh upregulates Wg
Wg upregulates En
En downregulates Hh

Question 2

What are the 2 modifications of the Wnt protein before its secretion?

Answer 2

1. Palmitoylation

2. Palmitoleic acid addition

Question 3

Which drosophila genes are involved in the reception and transmission of the Wnt signal to the nucleus?

Answer 3

Frizzled
Dishevelled
Groucho

Question 4

Example of a Wnt inhibitor

Answer 4

Dickkopf1 (Dkk1)

Question 5

What does loss of axin1 in zebrafish embryos cause?

Answer 5

Posteriorisation of the anterior brain- loss of eyes

Question 6

What does Wnt do in intestinal crypts?

Answer 6

Wnt is required for the maintenance of stem cells

Wnt expressed by the stroma- below the crypts

Question 7

Examples of 3 diseases associated with Wnt signalling

Answer 7

1. Tetra amelia syndrome- absence of limbs
2. Increased bone density (insensitive to DKK)
3. Tooth agenesis (missing teeth)

Question 8

What does the loss of the APC gene cause? And how does this link to adenomatous polyposis?

Answer 8

Loss of the APC gene can cause ectopic Wnt signalling
Adenomatous polyposis (heterozygous for APC gene)- polyps caused by random loss of remaining WT copy of APC gene- resulting in activation of Wnt- proliferation of cells forming polyps