Neural Induction (in addition to those from MoD)

Question 1

what initially inhibits BMP expression in the dorsal region of the xenopus?

Answer 1

• goosecoid expression induced by the siamois/twin and smad2/4 interactions in the dorsal mesoderm at the start of gastrulation.

Question 2

what does goosecoid inhibits the expression of?

Answer 2

WNT8 and BMP4

Question 3

what neural gene does BMP repress the expression of?

Answer 3

neurogenin among others

Question 4

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

Answer 4

1. sizzled vent 1 and vent 2
2. lose szled
3. lose vent 1
4. gain myf5
   5 chordin

Question 5

how was it shown that the different endomesodermal structures that the organiser gives rise to are responsible for the different AP patterning?

Answer 5

• 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

Question 6

what experiment showed that the first cells to enter the zebrafish gastrula from the SO induce head and the later ones induce trunk?

Answer 6

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

Question 7

what are the most anterior regions of the head an brain underlain by?

Answer 7

pharygneal endodern (anterior endoderm) and prechordal plate plate (head mesoderm).

Question 8

what does the leading edge of the blastopore lip contribute to? what is their role?

Answer 8

the anterior endoderm and the prechordal plate. to allow the patterning of anterior structures of the anterior head by inhibiting WNT and BMP

Question 9

what happens when you inject cerberus into the ventral side of the xenopus blastomere?

Answer 9

you get a second head

Question 10

what does cerberus inhibit?

Answer 10

BMP and WNT and nodal

Question 11

where is cerberus expressed during gastrulation?

Answer 11

• in the deep cells of the early blastopore lip.

Question 12

how does cerberus protein inhibit BMP WNT and nodal?

Answer 12

by binding outside the cell

Question 13

what does the pharyngeal endoderm secrete?

Answer 13

cerberus, dkk1 frzb and IGF

Question 14

what does the prechordal plate mesoderm secrete?

Answer 14

dkk1 frzb IGF chordin noggin

Question 15

what does the notochord release?

Answer 15

chordin, noggin and follistatin

Question 16

what signals does the epidermis need to form

Answer 16

BMP and WNT

Question 17

what signals does the trunk and spinal cord need to form?

Answer 17

inhibition of BMP but WNT expression

Question 18

what signals are required for head and brain to form?

Answer 18

inhibition of BMO and WNT

Question 19

what does dkk1 inhibit?

Answer 19

wnt

Question 20

how does IGF inhibit WNT and BMP

Answer 20

acts on a RTK which interferes with the signal transduction pathways of BMPS and WNTS

Question 21

what is the dominant posteriorising factor in the neural tube?

Answer 21

XWNT8

Question 22

what happens if you add XWNT8 to the early embryo?

Answer 22

lose anterior neural sturctures

Question 23

what is the role of FGF In AP patterning thought to be?

Answer 23

they appear to be critical in allowing cells to respond to the WNT signal

Question 24

what is the role of RA in AP patterning though to be?

Answer 24

• high levels in the posterior end and exists as a gradient

Question 25

what is the evidence that the presence of WNT inhibits the formation of anterior structures?

Answer 25

• 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.

Question 26

how does WNT signalling confer posterior fates?

Answer 26

activating transcription of posterior hox genes