lecture 4- brain vs spinal cord Flashcards
as gastrulation proceeds, what is established?
an AP gradient of Wnt signalling
Where are Wnts and Wnt antagonists expressed in the neural plate
Wnts= posteriorly
Wnt antagonists= anteriorly
what do neural cells exposed to low Wnt signals become
brain
what do neural cells exposed to high Wnt signals become
anterior spinal cord
why is Wnt low anteriorly
because Wnt antagonists are expressed in prechordal mesoderm
what is the main Wnt antagonist
Dickkopf
which part of the neural plate doesnt express Wnt antagonists
the notochord
How do we know the neural plate is becoming regionalised?
we look at expression of transcription factors with in situ hybridisation
what does Otx 2 expression induce
forebrain
what does Hox gene expression induce
anterior spinal cord
How do we know the prechordal mesoderm is the source of signals that regionalise the neural plate?
gain/loss of function
neurula anterior mesoderm in early gastrula induces extra head w brain
neurula posterior mesoderm in early gastrula induces trunk and tail
How do we know that the ability of the prechoral mesoderm to promote brain is mediated by wnt antagonists ?
gain/loss of function
over expression of Dickkopf = bigger forebrain
knockout of Dickkopf = lose forebrain
what kind of signalling develops the anterior nervous system
wnt-wnt antagonist
why is the posterior spinal cord formed by a different mechanism to the anterior spinal cord
due to changes in in properties of the organiser cells
what is spinal cord segmentation due to
different hox genes having different anterior limits of expression
which leads to different coding
