L5 - Neural crest formation and dorso-ventral axis Flashcards
What is D-V regionalisation (patterning)?
it describes the transition from an unpatterned neural tube to a tube that is patterned along the dorso-ventral axis
What is the location of neural plate border cells and what do they become?
Neural plate border cells are at the neural-ectoderm cells.
They give rise to neural crest cells and roof plate cells.
What are the 4 steps in neural crest formation?
step 1: There is first the neural plate border cells which is an early border established between the neural plate and ectoderm. Specific transcription factors such as Msx are induced (at intermediate BMP signalling).
step 2: a transcriptional signature develops due to instrinsic and extrinsic events. It shows that transiently defines neural plate border cells.
step 3: other TFs are upregulated at the neural plate border cells. These TFs cause the neural plate border cells to go to a neural crest cell identity.
–> so this set of transcription factors then acts intrinsically to upregulate a whole other set of genes - so then genes that control cell proliferation, multipotency and survical are transcriptionally transcribed.
step4: at the same time, neural crest cell TFs upregulate a futher set of genes. These promote epithelial-mesenchymal cell transition. neural crest cells then delaminate (divide into layers) from the border region and migrate away.
step 5: after the neural crest cells have migrated away, the neural tube finally closes.
What is the importance of neural crest cells?
They are also known as the 4th germ layer - important as can give rise to a number of different types of cells of the body. e.g PNS and enteric system.
What is the origin and role of roof plate cells?
● Understanding nature of signals (BMPs) that derive from roof plate and their role in patterning the dorsal neural tube
When the neural plate border cell does not become neural crest cells, they become the roof plate border cells.
They are important in final step of neurulation and dorsal neural tube patterning.
- RP cells upregulate BMPs - they induce expression of TFs such as Pax genes.
- Pax TFs intrinsically cause the neural tube progenitors to get ‘dorsal identities’.
- Pax genes also induce BMPs so initiate a relay of BMP signalling in the dorsal neural tube.
Why do many BMPs contribute to dorsal patterning?
The roof plate expresses many different BMPs, which each induce a diff dorsal type.
It depends on the different threshold concentration, causes a certain fate to be adopted.
So morphogen/fate = depends on activation threshold.
● Describe cell types that develop in dorsal regions of the neural tube
cells that differentiate dorsally =
- roof plate cells
- neural crest cells
- diff classes of dorsal sensory relay interneurons.
What are dorsal progenitors induced by?
Induced by BMPs, with bilateral symmeyry, and prefigure/predict defined classes of dorsal spinal neurons. also by Wnt
What are dorsal progenitors induced by?
Induced by BMPs, with bilateral symmeyry, and prefigure/predict defined classes of dorsal spinal neurons. also by Wnt
