Neural Induction (in addition to those from MoD) Flashcards
what initially inhibits BMP expression in the dorsal region of the xenopus?
- goosecoid expression induced by the siamois/twin and smad2/4 interactions in the dorsal mesoderm at the start of gastrulation.
what does goosecoid inhibits the expression of?
WNT8 and BMP4
what neural gene does BMP repress the expression of?
neurogenin among others
list the gradient of genes that are induced and then lost as you move from the ventral BMP high region of the xenopus to the dorsal region - showing it acts as a morphogen
- sizzled vent 1 and vent 2
- lose szled
- lose vent 1
- gain myf5
5 chordin
how was it shown that the different endomesodermal structures that the organiser gives rise to are responsible for the different AP patterning?
- four sections from the archenteron plate were taken and grafted into the blastoceols of the early embryo - the most anterior section produced anterior facial structures such as the oral apparatus, then the next produced head structures, then hindbrain structures and the most posterior induced dorsal trunk
what experiment showed that the first cells to enter the zebrafish gastrula from the SO induce head and the later ones induce trunk?
when you graft the BL from an early gastrula you get whole axis but when you graft from old you dont get anterior structures- can even just get secondary tails
what are the most anterior regions of the head an brain underlain by?
pharygneal endodern (anterior endoderm) and prechordal plate plate (head mesoderm).
what does the leading edge of the blastopore lip contribute to? what is their role?
the anterior endoderm and the prechordal plate. to allow the patterning of anterior structures of the anterior head by inhibiting WNT and BMP
what happens when you inject cerberus into the ventral side of the xenopus blastomere?
you get a second head
what does cerberus inhibit?
BMP and WNT and nodal
where is cerberus expressed during gastrulation?
- in the deep cells of the early blastopore lip.
how does cerberus protein inhibit BMP WNT and nodal?
by binding outside the cell
what does the pharyngeal endoderm secrete?
cerberus, dkk1 frzb and IGF
what does the prechordal plate mesoderm secrete?
dkk1 frzb IGF chordin noggin
what does the notochord release?
chordin, noggin and follistatin
what signals does the epidermis need to form
BMP and WNT
what signals does the trunk and spinal cord need to form?
inhibition of BMP but WNT expression
what signals are required for head and brain to form?
inhibition of BMO and WNT
what does dkk1 inhibit?
wnt
how does IGF inhibit WNT and BMP
acts on a RTK which interferes with the signal transduction pathways of BMPS and WNTS
what is the dominant posteriorising factor in the neural tube?
XWNT8
what happens if you add XWNT8 to the early embryo?
lose anterior neural sturctures
what is the role of FGF In AP patterning thought to be?
they appear to be critical in allowing cells to respond to the WNT signal
what is the role of RA in AP patterning though to be?
- high levels in the posterior end and exists as a gradient
what is the evidence that the presence of WNT inhibits the formation of anterior structures?
- studies of dissociated animal caps have shown that they differentiate the most anterior region of th nerve system (the forebrain. adding increasing concentrations of WNT proteins to th medium transforms this anterior neural tissue into more posterior neural tissue, with low concentrations producing mid brain, intermediate producing hindbrain and high producing spinal chord.
how does WNT signalling confer posterior fates?
activating transcription of posterior hox genes
