Lecture 10 - Growth and Cancer Flashcards
What drives the cell cycle forwards?
The kinases Cyclins and Cdks
How do drosophilia grow ?
- Form a Syncytium- lots of nuclei in ONE CELL
- First 14 cycles of cell division is rapid (only S and M).
- Inside 14th cycle it slows and phase G1and G2 is introduced.
What is String protein and how is it relevant to the cell cycle ?
String protein, after 14th cycle maternal string runs out you are only left with foetal string
String - activates Cdks which drives the cell cycle
It is first expressed in the mesoderm (one of the last bits to form because tribble is expressed in mesoderm as well, tribble inhibits string. because you need time to form ventral furrow)
What does the rate of cell division in dropholia embryo depend on ?
Rate of cell divison in drosopholia embryo depends on cell location.
This creates mitotic domains, this is all based on String
What are the 2 ways in which organs grow?
Intrinsically and extrinsically
How can organs grow intrinsically?
Intrinsically - the organ knows the size it needs to be
How can organs grow extrinsically
The body and surrounding areas signal to the organ
What is organ size dependent on ?
Organ size is dependent on organ size not cell number
What was the experiement using a thymus and spleen to prove ex and intrinsic growth ?
- Took the thymus of a dif organism and transported it into another one
- The thymus stayed the same ze
- Whe done with a spleen the spleen got smaller
- Spleen was being controlled intrinsically/systemic
What are the 2 growth pathways?
TOR pathway
Hippo pathway
What is the difference between TOR and Hippo pathways ?
TOR - increases cell size
Hippo - (MST1/2) limits organ size
What does Hippo do after activation?
Hippo activates 3 proteins. YAP, TAZ and Yka
When Hippo is activated these proteins are not in the nucleus and prevents cells from increasing in size
HIPPO inactive stimulates cell growth, blocks things because it is big
Mutation in HIPPO = overgrowth
What does the size of drosophila depend on ?
In drosophila its size depends on insulin signalling
Insulin-defiecient = remain small with smaller and fewer cells
Maternal environment influences growth
What does the size of a human depend on ?
In humans it depends on our second growth spurt and insulin and growth hormones
How are human growth hormones released?
- GHRH, released from hypol=thalamus
- Causes pituitary gland to release growth hormone
- Somatostatin is also released from the hypothalamus but inhibits growth hormone release.
- Growth hormone allows IGF to be released
- IGF is released from the liver or local cells