Induction and signalling

Question 1

What is induction?

Answer 1

A cell/tissue instructs neighbouring cells to develop in a certain way. Directs morphogenesis in neighbouring cells

Question 2

What was the experiment done by Spemann that showed the process of induction?

Answer 2

Used amphibian eggs and transplanted cells to other parts of the embryo

Question 3

What did Spemann’s experiment show?

Answer 3

A new intestinal tract and new body axis formed where cells from the dorsal blastopore lip had been transplanted

Question 4

What did Spemann conclude after his experiment showing induction?

Answer 4

The dorsal blastopore lip has the ability to organize the development of surrounding cells

Question 5

What is instructive induction?

Answer 5

The signalling cell/tissue directs something specific to occur

Question 6

What is permissive induction?

Answer 6

Certain events are allowed to occur if the right signal is received at the right time

Question 7

What did the experiment on differential cell adhesion involve doing?

Answer 7

Digested epidermal and neural cells (aka separated them and broke all adhesion) and mixed them together. They then aggregated into a ball with the epidermal cells on the outside and the neural cells on the inside

Question 8

Why were the neural cells in the middle of the ball in the differential cell adhesion experiment?

Answer 8

They had stronger adhesive forces, so packed tighter together

Question 9

What is a cadherin?

Answer 9

Calcium dependent adhesion molecules. They are anchored to the cytoskeleton inside a cell and reach out to form connections with cadherins coming out of other cells, sticking them together

Question 10

What molecules anchor cadherins to the cytoskeleton?

Answer 10

Catenins

Question 11

What happens when cadherins are knocked out?

Answer 11

Neural tube can’t form properly because the cells can’t stick together enough

Question 12

What are the 5 types of cadherins?

Answer 12

E-cadherin (embryo, adult epithelial tissue), P-cadherin (attach placenta to uterus), N-cadherin (nerve cells), R-cadherin (retina), protocadherins (no intercellular actin binding)

Question 13

What is the quantitative aspect of cadherin interactions?

Answer 13

More cadherins = stronger adhesion

Question 14

What is the qualitative aspect of cadherin interactions?

Answer 14

Strength of adhesion depends of type of cadherins present

Question 15

What is the function of integrin?

Answer 15

Attachment to the extracellular matrix. They extend out of the cytoplasm and attach to fibronectin. Used for communication from the extracellular matrix

Question 16

What is a juxtacrine signal?

Answer 16

The neighbouring cells interact through complementary receptors

Question 17

What is the receptor for Delta?

Answer 17

Notch

Question 18

What happens inside the cell when Delta binds to Notch?

Answer 18

A protease cuts Notch and the cut portion influences transcription

Question 19

What is an endocrine signal?

Answer 19

Signal over a long distance

Question 20

What is a paracrine signal?

Answer 20

Signal over a local, short distance

Question 21

What is an autocrine signal?

Answer 21

Signal acts back on the cell

Question 22

What are the 4 paracrine family signalling pathways that we covered?

Answer 22

FGF family pathways, Wnt, Hedgehog, TGF pathways

Question 23

What is the signal in an FGF family pathway?

Answer 23

FGF or a similar growth factor molecule

Question 24

What is the receptor in an FGF family pathway?

Answer 24

Tyrosine kinase receptors that will autophosphorylate and dimerize

Question 25

What sort of response is typically caused by an FGF pathway?

Answer 25

Cell division. The downstream products act in the nucleus

Question 26

What is the signal in the Hedgehog pathway?

Answer 26

Hedgehog

Question 27

What is the receptor in the Hedgehog pathway?

Answer 27

Patched

Question 28

What does the Patched receptor act on?

Answer 28

Smoothened

Question 29

What does Smoothened act on?

Answer 29

Cubitus interruptus (Ci)

Question 30

What are the steps in the Hedgehog pathway?

Answer 30

Hedgehog - (inhibits) - Patched - (inhibits) - Smoothened - (activates) -> Ci

Question 31

What type of pathway is Hedgehog?

Answer 31

Double negative

Question 32

What is the cellular response when Hedgehog is being received?

Answer 32

Patched is inhibited, so it releases Smoothened which activates Ci. Ci activates gene expression for normal development

Question 33

What is the cellular response when Hedgehog is not being received?

Answer 33

Patched is inhibiting Smoothened, so Ci is not activated. No gene expression and get abnormal development

Question 34

What are the steps in the Wnt pathway?

Answer 34

Wnt - (activates) -> frizzled - (activates) -> dishevelled - (inhibits) - GSK3 - (inhibits) - beta catenin

Question 35

What is the signal in the Wnt pathway?

Answer 35

Wnt

Question 36

What is the receptor in the Wnt pathway?

Answer 36

Frizzled

Question 37

What is the cellular response when the cell is receiving Wnt?

Answer 37

Beta catenin doesn't get degraded and acts as a transcription factor

Question 38

What is the cellular response when the cell is not receiving Wnt?

Answer 38

Beta catenin gets degraded/stays attached to cytoskeleton and doesn't activate gene expression

Question 39

What are the steps in the TGF-beta family pathways?

Answer 39

TGF-beta -> Ser/Thr kinase receptor -> Smad -> transcription

Question 40

What is the receptor in the TGF-beta family pathways?

Answer 40

A serine/threonine kinase receptor that will autophosphorylate and dimerize

Question 41

What is the cellular response when the cell is receiving TGF-beta?

Answer 41

Smad is active and either turns on or off transcription depending on the environment

Question 42

What is the cellular response when the cell is not receiving TGF-beta?

Answer 42

Smad isn't active and transcription will not change