L1: Neural Induction

Question 1

what does the gastrula contain

Answer 1

3 germ layers (ectoderm, endoderm, mesoderm)

Question 2

what does the ectoderm form

Answer 2

epidermis
neural tissue (neural crest and neural tube)

Question 3

spemann organiser transplantation in newts

Answer 3

if organiser removed then no anterior structures (head)
transplant of organiser on ventral side - twinned embryo (2 heads)

Question 4

where is the notochord derived from

Answer 4

organiser

Question 5

what do earlier signals form

Answer 5

anterior structures (brain and head)

Question 6

what do later signals form

Answer 6

posterior structures (spinal cord and tail)

Question 7

what is the default model of neural induction

Answer 7

neural tissue

Question 8

animal cap cultures

Answer 8

culture intact - epidermis
cultures dissociated - neural cells (no signalling)

Question 8

what are the signals for the epidermis

Answer 8

bone morphogenetic protein (BMP) in animal cap of ectoderm

evidence:
BMP+dissociated cells from animal cap = epidermis

Question 9

what inhibitor does neural tissue require

Answer 9

BMP inhibitor

Question 10

what does the ectoderm close to the spemann organiser (dorsal lip) become

Answer 10

neural tissue

Question 11

UV light

Answer 11

ventralised embryo
no dorsal structures

Question 12

Lithium

Answer 12

hyperdorsalised embryo

Question 13

Li + UV embryo

Answer 13

extract polyA mRNA of hyperdorsalised embryo
normal dorsal patterning

Question 14

name 3 BMP antagonists

Answer 14

Follistatin
Chordin
Noggin

Question 15

name extracellular antagonists

Answer 15

smad6&7 (induces neural plate border markers in chicks)

Question 16

role of noggin in normal and ventralised embryos

Answer 16

noggin + normal embryo = dorsalised embryo
noggin + ventralised embryo = normal embryo

Question 17

FCN MO

Answer 17

no neural plate
increase in BMP signalling

Question 18

FCN injection (rescue)

Answer 18

rescues neural plate markers (sox2, myoD, Shh)

Question 19

what does the KO of chordin and noggin cause

Answer 19

loss of anterior structures

Question 20

what is the organiser called in mammals

Answer 20

henson’s node

Question 21

use of krox20

Answer 21

hindbrain formation

Question 22

what occurs if wnt3a and activin is added to embryonic SC

Answer 22

induces a primitive streak
induces 2nd axis

Question 23

what can generate an ectopic PS in chicks

Answer 23

chordin
(alone does not produce neural tissue)

Question 24

what does NOT alone produce neural tissue

Answer 24

misexpression of BMP antagonists

Question 25

FGF expression in chicks

Answer 25

FGF4 in node - weak
FGF8 in node - strong

Question 26

FGF inhibition

Answer 26

inhibits sox3 erni (early response to neural induction gene)

Question 27

what does FGF require for a 2nd axis

Answer 27

Churchill (ChCh)

Question 28

how does ChCh block mesoderm induction

Answer 28

interacts with SIP1 (smad interacting protein) to block mesoderm induction by FGF

Question 29

role of FGF dependent Churchill

Answer 29

smad1 inhibition
tissue response to BMP antagonists

Question 30

FGF in amniotes

Answer 30

needed for neural induction in xenopus

induces genes also induced by organiser but not enough to induce a nervous system