Neurogenesis in the forebrain

Question 1

Initial neurogenesis in the rostral brain

from flat disc to hollow tube

Answer 1

2 process
follding up of neural plate to form neural tube
and 
in rostral part in the brain 
formation of primary brain vesicles
patterning
forming of forebrain prosencephalon di and telencephalon
midbrain mesencephalon
and hindbrain rhombencephalon

formation of the first neurons and difrt connections

Question 2

the early axon scaffold

conserved in vertebrates

Answer 2

formed by first neurones in th ebrain pioneers major pathway in t he CNS
consists of
longitudinal tracts
transversal - perpendicular direction
and commissural tracts - in anamniote i.e. zebrafish zenopus form larval nervous system

Question 3

in the chick
forebrain hypothamamus joins mlf to form the longitudinal tract
midbrain desecending tract

Answer 3

MLf neurons first neurons in the forebrain diencephalon

gene expression in this region:

starting w the neural ectoderm
neural progenitor cells characterised by expression of Sox 2
neurogenic region marked by neurogenin2 expression
region where neurons can form small region in which lateral inhibition acts to select cells to undergo differentiation marked by neuroD4

neurogenin 2 - neuroaonal determination
neuroD4- differentiation
Crap1 - differentiating neurons - cellular retinoic binding protein
ddifferentiation = mature neurons

Question 4

how do we define wthere neurogenin 2 is expressed initially
does fgf control mlf neurogemesis
fgf signalling centre = isthmus and anterial neural ridge = as far from the mlf region as can be
we know fgf signalling inhibits nurogenesis in the spinal cord

Answer 4

test
cornish pasy culture of chick embryos
take chick embros out of the egg at an early stage
blastoderm and embryo in the middle
can fold it over venral side up
and take the embryos into culture in a defined medium
allows us to apply specific pharmacological agonists or antagonists
result w 3 embryos
always looking for neuroD4
looking for neurogenesis
1 control
chemical - not water solvent so dissolved in DMSO
solvent control
applied increasing contration 1 nmor one micromoler oh an inhibitor to the fgf recpetor

resullt = increase of neurod4 expressing cells expanding into the teritory that would normalled be devoid of neurogenesis

conc
fgf discontrols l the expression of neurogenin2
the neurons are restricted to the diencephalon to the forebrain region
boundary betweeen the diencephalon and the mesencephalon is set up in the interaction between 2 transcription factors
en1 induced by fgf8 signalling
and is expressed up to the midbrain forebrain boundary
pax6 is repressed by fgf8
and is expressed in the forebrain up to the forebrain midbrain bounddary

pax6 and eng1 repress each other
pax6 switched on neurogenin 2 in the spinal cord
in the forebrain - fgf acts through the interaction w eng1 and pax 6