NEURAL INDUCTION Flashcards
In worms, insects and vertebrates, neural precursors first form where?
At the surface, next to the future skin (ectoderm) on one side and next to the mesoderm on the other side.
What is happening for the ectoderm to change their identity and become neurogenic?
A signal coming from the mesoderm.
How does the body decide to put aside cells to become the neural plate?
Depends on how much BMP is or is not received.
What is BMP4 in Drosophila?
Decapentaplegic (dpp)
What is BMP7 is Drosophila?
Screw
What is BMP1 in Drosophila?
Tolloid
What is Chordin in Drosophila?
Short gastrulation
Although many genes have different names in vertebrates and non vertebrates, it shows what?
The body plan is conserved throughout vertebrates and there are surprising similarities between vertebrates and invertebrates.
What do early BMPs code for?
Non neural homeobox genes.
If BMP/dpp is antagonised, what happens.
The cells that do not receive BMP become neural.
How is BMP /dpp inhibited?
If chordin/short gastrulation binds to BMP/dpp, then BMP/dpp cannot bind to its receptor. If the receptor is not activated there is not pSMAD157 pathway - low SMAD4 and so the cell undergoes epidermal differentiation.
What other transcription factors are known for helping neural differentiation?
Sox genes
As vertebrate development progresses, what happens to the neural plate?
The neural plate rolls up to form the neural tube - this is neurulation.
Our understanding of how the neural plate forms and how neurulation occurs came from studies of which vertebrate?
Xenopus
Following fertilisation of Xenopus, the egg undergoes mitotic cleavages and give rise to a hollow ball of cells consisting of what?
Three germ layers: ectoderm, mesoderm, endoderm
What is the difference between the the Xenopus germ layers and the human germ layers?
The germ layers consist of the same ectoderm, mesoderm and endoderm but in Xenopus these are shaped in a hollow ball and in humans, this is flat plate.
What is meant by neural induction?
The neural embryonic plate is set aside from other parts of the ectoderm.
The neural pate forms when BMP antagonists prevent the BMP ligand from binding to its receptor.
The mesoderm is not uniform, a specialised type of mesodermal cells is induced that collectively is called what?
The organiser/node
What happens in the organiser/node?
The cells express a transcription factor that acts intrinsically to activate further genes that encode for BMP antagonists.
What is the transcription factor in the node/organiser that induces activation of BMP antagonist genes.
Goosecoid
Give examples of BMP antagonists.
Chordin
Noggin
Follistatin
BMP antagonists diffuse from the organiser/node. Where diffusion is highest, what happens to these cells?
They become neural.
In order to localise and visualise expression of different proteins, what studies should be done?
In situ hybridization
What are the stages of mesoderm induction and patterning?
- Low levels of Nodal gives for ventral mesoderm
- High levels of Nodal gives the Organiser/Node
- Signals from the organiser acts to inhibit BMPs
- Antagonism of BMPs in ectoderm lead tissue to acquire neural identity