Signaling Pathways

Question 1

Define and describe the process of lateral inhibition.

Answer 1

Type of signaling between a dominant cell and neighboring cell in which the dominant cell begins to differentiate along a certain pathway. Represses genes in the neighboring cellls. Delta Notch pathway.

Question 2

Describe signal transduction pathways.

Answer 2

They are established when a ligand binds to receptor and results in signals being transmitted to the nucleus of cell.

Question 3

What are four common signaling factor families?

Answer 3

1. Transforming Growth Factor B Superfamily
2. Fibroblast GF
3. Hedgehog
4. Wnt

Question 4

What family does Activin and Inhibin belong to?

Answer 4

TGF-B

Question 5

What does Mullerian Inhibiting substance belong to?

Answer 5

TGF-B

substance that results in inhibition of Müllerian ducts

Question 6

What does Decapentaplegic belong to?

Answer 6

TGF-B

Question 7

What family does Vg1 belong to?

Answer 7

TGF-B

Question 8

What family does BMP-1…BMP-15 belong to?

Answer 8

TGF-B

Question 9

What family does nodal and Lefty belong to>

Answer 9

TGF-B

Nodal: refers to notochord

Question 10

What family does Glial cell line derived neurotrophic factor belong to?

Answer 10

TGF-B

Factor that changes dev. Potential from becoming neuron to glial cell

Question 11

What family consists of a large pro region and a bio active region?

Answer 11

TGF-B1
The large pro region is cleaved from the bio active region and two of each regions are secreted. The pro regions keep the bio active dimmer inactive until they are cleaved.

Question 12

What do Bone morphogenetic proteins do, and what family are they part of?

Answer 12

They inhibit other processes in the embryo. They bind to bioactive dimers and prevent them from binding to receptors. Part of TGF-B Superfamily.

Question 13

Describe the Fibroblast Growth Factor Family.

Answer 13

Regulated by modification of interaction with heparin proteoglycans in the receptor complex and there are 22 members.

Question 14

Describe the Hedgehog family.

Answer 14

Related to segment polarity molecule in drosophila, it includes Desert, Indian, and Sonic hedgehog

Question 15

Describe the Wnt Family.

Answer 15

Stands for Wnt tumor found in kidneys.

Related to segment polarity genes in drosophila and interacts with components of the ECM.

Question 16

Describe cell surface receptors.

Answer 16

There are two types:

Ones that have intrinsic protein kinase activity or ones that utilize a second messenger system.

Question 17

Describe the Delta Notch pathway.

Answer 17

Delta is the signaling molecule on the dominant cell and Notch is the receptor on a neighboring cell. This pathway requires cell to cell contact.

Notch is cleaved and the intracellular domain complexes with Deltex and enters the nucleus and then binds to suppressor of hairless which then binds to enhancer of split resulting in repression of gene expression.

Question 18

Describe the RTK Pathway.

Answer 18

Utilized by fibroblast growth factor signaling molecules and by transforming growth factor B signaling molecules.

Question 19

Describe the hedgehog pathway.

Answer 19

Sonic hedgehog protein is complexed with cholesterol after translation and Shh-Cholesterol is trans located to cell surface and then inhibits the inhibitory actions of patched on smoothened on the target cell.

Uninhibited smoothened signals release of transcription Gli from complex on microtubules and Gli translocates to nucleus.

Doesn’t require cell to cell contact.

Question 20

Describe the Wnt Signaling Pathway.

Answer 20

When went is not present B-Catenins are bound to an intracellular destruction complex within the target cell.

Wnt ligand binds to Frizzled (receptor). Frizzled interacts with Disheveled. Disheveled prevents degradation of B-Catenins by destruction complex. B-Catenins can then trans locate to nucleus and activate TF.

Question 21

Why do we have complex signaling pathways?

Answer 21

Dr. Anderson says: Having multiple steps allows for large amounts of variations and different responses with a small number of molecules involved in the process.

Question 22

Describe the MicroRNA Pathway.

Answer 22

MiRNA’s are non coding RNA’s that influence gene expression. Two major groups:

1. PiRNA’s: act during gametogenesis
2. Endo-siRNA’s: expressed in somatic tissues throughout development

Question 23

Retinol pathway?

Answer 23

Retinol is the signaling molecule and binds to extra cellular retinol binding protein.
Retinol binding protein binds to membrane RBP and retinol is released into cytoplasm and binds to CRBP1 and after enzymes act retinoids acid is bound to CRABP1 and trans located to nucleus and rationing acid binds to dimmer RXR-RAR which binds to RARE to activate transcription.