Animal and Organ Size Control (L26, 27)

Question 1

Extrinsic Growth Control Mechanism

Answer 1

Hormones, nutrients, cell-cell/organ-organ communication

Question 2

Intrinsic Growth Control Mechanism

Answer 2

Genetic programmes within cells.
Cell death
Cell proliferation
Cell size
Protein synthesis

Question 3

MVW

Answer 3

Minimum Viable Weight

o Minimum weight to survive metamorphosis, eclose to adult when starved

Question 4

CW

Answer 4

Critical Weight
o Minimal size at which starvation no longer delays metamorphosis
Release ecdysone when reached.
Release ILPs from fat body and imaginal discs.

Question 5

Ecdysone

Answer 5

Released from ring gland.

Initiate morphogenesis.

Question 6

Ring Gland

Answer 6

Impact organ size.
Small ring gland = longer time to pupation = eat more = bigger.
Release ecdysone.

Question 7

Nutrition-Tor Signalling

Answer 7

1. Nutrients sensed by slim/fast receptor
2. Phosphorylates and activates TOR (kinase)
3. TOR phosphorylates S6K and inhibits 4EBP
4. S6K phosphorylates S6 ribosomal protein (maturation and connection of 40S and 60S). 4EBP would usually inhibit translation
5. Protein synthesis occurs and allows cell growth

Question 8

Insulin Like Peptides (ILPs) and Insulin Signalling

Answer 8

Growth factors.

1. ILPs bind insulin receptor which is phosphorylated
2. The receptor recruits IRS
3. IRS recruits many proteins including PI3K
4. PI3K phosphorylates Akt kinase
5. Akt phosphorylates the FOXO transcription factor
6. FOXO drives cell growth (protein synthesis) and proliferation (DNA synthesis)

Question 9

TSC1/2

Answer 9

• Part of TOR pathway

* Act on TOR, promote protein synthesis and cell growth

Question 10

SWH Pathway

Answer 10

Intrinsic growth regulation.
Inhibit cell death (diap1)
Increase cell proliferation (cycE)
Activated when Yki enters nucleus.

Question 11

Fat

Answer 11

Apical.

Act on SWH pathway.

Question 12

KEM complex

Answer 12

FERM family: Kibra, Merlin, Ex

Act on SWH pathway