Patterning of the telencephalon - PICS Flashcards
Where are most morphogens located in the developing brain?
Midline
What morphogens are located in the anterial neural ridge?
Fgf8 & other Fgf families
What morphogens are located in the cortical hem?
Wnts and BMPs
What morphogens are located in the anti-hem?
FGF15 - used to antagonise the affects of other Fgf family members at the anterial neural ridge
What does the ventral part of the diecephalon express?
Shh
What are the markers for the cortical hem?
Lhx2, Emx1/2
What are the markers for the dorsal pallium?
Ngn12, Pax6
What are the markers for the ventral telencephalon?
Mash1, Dlx1/2, Gsh 1/2
What is the pallium and what kind of neurons are produced here?
Dorsal part of the forebrain and it makes glutamatergic projection neurons
What is the tissue that forms in the pallium?
Choroid plexus and choroid roof aka the choroid field that gives rise to cells that produce tissue fluid
What is the subpallium?
It is the ventral part of the forebrain
What structure is in the subpallium and is made here?
Ganglionic eminences - produce GABAergic interneurons
What is the cortical hem and what does it do?
Organising centre that’s vital for patterning of the cortex
What does the archicortex give rise to?
This gives rise to the hippocampus
What does the neocortical domain give rise to?
Cortex
What is the paleocortex give rise to?
Many structures within the limbic system e.g. hippocampus and cingulate gyrus
What are the dorsal markers of the telencephalon?
Pax6, Tbr2, Ngn2, Emx1
What are the ventral markers of the telencephalon?
Gsh2, Gsh1 and Mash1
How is the cortex affected by double mutants of Emx2 and Pax6?
Dorsal part appears to be reduced/ gone
What happens if you completely eliminate Emx2 but leave one copy of Pax6?
The brain looks weirder but you will still have the expression of the dorsal markers
What happens if you remove Pax6 but leave one copy of Emx2?
Brain looks quite weird but you can still detect some dorsal markers
What happens if both Emx2 and Pax6 are ablated from the brain? (4 marks)
No dorsal markers
This shows there is no dorsal plate (tissue) and any left over tissue could be ventral
However it may be positioned dorsally but because its ventral tissue the markers are ventral
What do ventral (subpallial) markers do in Pax6 mutant embryos?
The markers expand dorsally
What happens to the cortex in the absence of Pax6?
Ventral marker DLX moves up with the cortex.
No Pax6 expression means that Mash1 is no longer restricted to the ventral region
What does the roof plate (uppermost dorsal part in neural tube) do? (2 marks)
- It invaginates at the level of the forebrain, and produces separation of the 2 hemispheres
- As it does this it specifies the different structures i.e. cortical hem, hippocampus and choroid plexus
What happens if the roof plate is removed?
Reduced expression of Lhx2 in forebrain
Smaller hemisphere
What do the effects of removing the roof plate show us?
That something is needed in the roof plate to stimulate the expression of Lhx2
What specific morphogen is expressed in the roof plate?
BMPs - these promote expression of Lhx2
How experimentally can you prove that BMPs are needed for Lhx2 expression and what does this show?
So - put beads containing BMP4 into forebrain explant
It was found that if you put the beads in it or around it there is no Lhx2 expression
Whereas if you put it at the border of empty cell, there is slightly higher Lhx2 expression
Shows the occurrence of regulation
What is the importance of Lhx2 expression?
With no Lhx2 expression found there’s a loss of cortical progenitors and neurons. Choroid plexus thickens and stretches up and round more of the cortex
What happens to the choroid plexus in the absence of Lhx2 expression?
Choroid plexus becomes more medial, marker Ttr is absent
What happens to the cortical hem in the absence Lhx2?
Wnt2b is not expressed and the structure becomes more medial
What happens to the telencephalon in the absence of Lhx2?
Foxg1 is not expressed and the structure condenses
