L1: Neural Induction Flashcards
what does the gastrula contain
3 germ layers (ectoderm, endoderm, mesoderm)
what does the ectoderm form
epidermis
neural tissue (neural crest and neural tube)
spemann organiser transplantation in newts
if organiser removed then no anterior structures (head)
transplant of organiser on ventral side - twinned embryo (2 heads)
where is the notochord derived from
organiser
what do earlier signals form
anterior structures (brain and head)
what do later signals form
posterior structures (spinal cord and tail)
what is the default model of neural induction
neural tissue
animal cap cultures
culture intact - epidermis
cultures dissociated - neural cells (no signalling)
what are the signals for the epidermis
bone morphogenetic protein (BMP) in animal cap of ectoderm
evidence:
BMP+dissociated cells from animal cap = epidermis
what inhibitor does neural tissue require
BMP inhibitor
what does the ectoderm close to the spemann organiser (dorsal lip) become
neural tissue
UV light
ventralised embryo
no dorsal structures
Lithium
hyperdorsalised embryo
Li + UV embryo
extract polyA mRNA of hyperdorsalised embryo
normal dorsal patterning
name 3 BMP antagonists
Follistatin
Chordin
Noggin
name extracellular antagonists
smad6&7 (induces neural plate border markers in chicks)
role of noggin in normal and ventralised embryos
noggin + normal embryo = dorsalised embryo
noggin + ventralised embryo = normal embryo
FCN MO
no neural plate
increase in BMP signalling
FCN injection (rescue)
rescues neural plate markers (sox2, myoD, Shh)
what does the KO of chordin and noggin cause
loss of anterior structures
what is the organiser called in mammals
henson’s node
use of krox20
hindbrain formation
what occurs if wnt3a and activin is added to embryonic SC
induces a primitive streak
induces 2nd axis
what can generate an ectopic PS in chicks
chordin
(alone does not produce neural tissue)
what does NOT alone produce neural tissue
misexpression of BMP antagonists
FGF expression in chicks
FGF4 in node - weak
FGF8 in node - strong
FGF inhibition
inhibits sox3 erni (early response to neural induction gene)
what does FGF require for a 2nd axis
Churchill (ChCh)
how does ChCh block mesoderm induction
interacts with SIP1 (smad interacting protein) to block mesoderm induction by FGF
role of FGF dependent Churchill
smad1 inhibition
tissue response to BMP antagonists
FGF in amniotes
needed for neural induction in xenopus
induces genes also induced by organiser but not enough to induce a nervous system
