Bio 1-L16-Cell Signalling in Development

what is induction

one group of cells influences the development of neighbouring cells

how is induction achieved at a molecular level

• they send signals to neighbouring cells

• the use paracrine signalling- secretion- genes turned on and off in response

explain signal transduction

it is the response of activation of a gene encoding TF- causes a cascade

major pathways in development

• Wnt- frizzles- positional info

• hedgehog - patched.smoothened- positional info- neural- ZPA

• FGF- FGF8- at all stages- AER, mesoderm

hedgehog signalling pathway?

1. hedgehog binds to patched receptor

2. moves smoothened to cell mebrane

3. gili transcription factor- becomes activated

what does hedgehog do in drosophila? and what happens when it is mutated?

• a segmentation gene

• establishment of segment boundaries

when mutated- caused a shorter body plan and ventral side was covered in bumps

hedgehog gene in the mouse? what does it do when mutated/transplated?

3 types- indian(cartilage to bone), sonic(neural tube and developing limbs) and desert(male reproductive system)

it is expressed in the ZPA- hedgehog is transplanted to the dorsal- it causes extra toes.

what else does sonic hedgehog control

the ZPA- sonic is a major active componenent

Fgf signalling what does it do- what happens

helps with limb development- has a relationship with AER. when AER is not present but if FGF8 is added- limb still grows

what does AER secrete?

FGF8- fibroblast growth factor 8

Wnt signallung- what is it in vertebrates and invertebrates?

• wingless- in dosphila- segmentation gene along with hedgehog

• 19 wnt in human and mice- developing limbs and nervous system and muscles

WNT signalling steps

• Wnt binds to frizzled

• Beta catenin is stabilised and released into cytoplasm and transported to the nucleus

• binds to Tf Tcf family and turns on gene expression

what does WNT develop in mice

• positional info

• cell proliferation

• limb development

• kidneys

• stem cell control

what happens when there are mutations in WNT in mice?

• no production- leads to loss of large area of the brain- as there is no paracrine signalling for development for. large part of the brain

what kind of cancer is Wnt linked to?

• colon cancer

  • APC controls how a signal is interpreted in a cell- keeps it OFF

    • in cancer- APC is mutated- even with no Wnt signal-acts like a Wnt signal and causes proliferation

what type of mutations lead to cancer

• proto oncogens- overdivide

• tumour supressors

what is the induction experiment? who and what animal and what’d it show?

spennman experiement- took a dorsal lip from one frog and transplanted to the other side of another

• development of double body plan

give a second example of inductio and in what animal? what signalling pathway

• c.elegans

• development of vulva is with 6 genes- anchor cell intimates a cascade and is concentration dependent

• EGF