Neural crest and ectodermal placodes Flashcards
Where do neural crest cells arise?
Where are placodes induced?
along the whole neural tube
induced at anterior positions
Wnt and BMP signaling: how does it look like where
a) epidermis
b) placodal cells
c) neural crest cells
d) neural cells are created?
a) BMP and Wnt present for extended period of time
b) Wnt induces BMP, but is then downregulated
c) Wnt induces BMP and remains active
d) Wnt only
What is the potency of neural crest cell derivatives and which are they?
multipotent
melanocytes, Schwann cells, sensory neurons in the PNS, neurons of autonomic nervous system, cartilage derivatives
What structure do the neural crest cells and placodes develop from and which proteins are active there?
neural plate border
Dll5, Pax3/7
Which TFs specifiy neural crest cells and which proteins are effectors in these cells?
specifiers: FoxD3, Twist, Snail
effectors: Rho, Kit, Ret, MITF
What are pharyngeal arches?
metameric structures
outpocketings of endoderm
create respiratory and feeding apparatus
What are the 2 migratory paths of the cranial neural crest cells and which structures do they give rise to?
stream to the frontonasal process
stream to the pharyngeal arches
give rise to cartilaginous structures
Hox negative anterior domain gives rise to facial skeleton
also, cranial sensory ganglia (extending out of rhombomeres)
What role do the neural crest cells play in the formation of anterior neural ridge?
induce FGF expression
no Fgf8 = no brain growth
What are the 2 migratory paths of the trunk neural crest cells and which structures do they give rise to?
ventral route: sympathetic adrenal ganglia, dorsal root ganglia, Schwann cells, adrenal medulla
dorsolateral route: melanocytes
Which gene regulatory networs control neural crest development?
GNR controlling the formation of the neural plate border (induced by Wnt, BMP)
GNR controlling specification of the neural crest (separating premigratory neural crest from preplacodal region)
GNR allowing delamination and dispersion of NCCs (Snail TFs, FoxD3, Sip1)
Neural crest specifiers that drive the transition to the migratory neural crest state (end of Noggin expression from somites is the signal for emigration of NCCs)
subcircuits that control neural crest diversification
NCCs are multipotent. Which signals influence their differentiation?
intrinsic:
no Hoxa2 in anterior cranial NCCs = facial skeleton; Hox presence gives rise to cartilage
extrinsic:
BMP from aorta;
glucocorticoids from the adrenal cortex inhibit neuronal differentiaton to get adrenomedullary cells
How can you use NCCs as a model for multipotent stem cells?
NCC cell culture:
remove the embryo, cut away from the yolk sac and the amnion
select the segment, dissociate in pancreating
cut away the lateral tissues before beginning dissociation
keep the cells in suspension
single cell cultures:
derived from adult tissues
e.g. nerves containing Schwann cells and melanocyte precursors
What are cranial placodes?
epidermal thickenings which produce delaminating sensory cells which will create sensory organs
(exception: lens placode - not neurogenic)
Name the placodes.
olfactory lens adenohypophyseal trigeminal otic epibranchial
What is essential for lens placode formation?
optic vesicle AND competent endoderm above it
