Post embryonic development and cancer
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3 ways to achieve growth
• Cell proliferation • cell enlargement • accretion of extracellular material
What drives the cell cycle?
Cyclins and CDKs
What happens in the first few cell cyles in drosophila?
Rapid and synchronous nuclear divisions Creates syncytial blastoderm No G phases
What happens at cycle 14 in drosophila?
Blastoderm becomes cellularized Well defined G2 phase change in the synthesis and distribution of string- zygotic string expression takes control
Where is string not causing cell proliferation and why?
Presumptive mesoderm Gene= tribbles- expressed here- blocks string
What determines overall size?
Rate and duration of growth
What determines the size of the adult drosophila?
Insulin signalling-> larval size-> adult size
What is IGF1 & IGF2?
Insulin-like growth factor, important for embryonic and adult growth
What stimulates and represses GH?
Stimulated by GHRH from the pituitary Repressed by somatostatin
What happens when Hippo is active?
Hippo phosphorylates Warts- phosphorylates Yki
What happens when Hippo is inactive?
Yki translocates to the nucleus and stimulates the growth and survival of cells
What does the Hippo pathway do?
Limit organ size
Examples of proto-oncogenes
Ras Raf EGFR
Examples of tumour supressor genes
RB P53 Patched
Examples of devlopmental signals which can cause cancer
Wnt Hedgehog
What are the hormones involved in metamorphosis?
Juvenile hormone= prevents Ecdysone= promotes
What causes metamorphosis in tadpoles?
Environ cues-> CRH-> TSH->Thyroxin If a certain level of thyroxin is reached- metamorphosis becomes irreversible