L19: Neural Crest & Eye Development

Question 1

origin of neural crest tissue

Answer 1

originate from lat margins of neural plate

initially epithelial in nature
then transform into mesenchymal cells for migratory purposes

Question 2

induction of neural crest tissue

Answer 2

induction from non-neural ectoderm:
BMPs and Wnts

induction from mesoderm:
FGF-8

Question 3

what factors are important in order for neural crest cells to break free and become migratory?

Answer 3

snail 1/2

foxd3

Question 4

list the migratory pathways for the 1st, 2nd, 3rd wave and emigrating neural crest cells

Answer 4

1st
ventral/sympathoadrenal path
2nd
ventrolateral path
3rd
dorsolateral path

Question 5

ligand/receptor pair guidance molecules

Answer 5

robo/slit
neuropilin/semaphorin
ephrin/eph

Question 6

early vs late migratory neural crest cells

Answer 6

early have most potential for differentiation

later can only dif into dorsal cells

latest can only form melanoblasts

Question 7

name the neural crest cell divisions

Answer 7

trunk
cranial
circumpharyngeal
cardia
vagal

Question 8

trunk neural crest

Answer 8

comprised of 3 migration pathways

1. sympathoadrenal path
2. ventrolateral path
3. dorsolateral path

Question 9

sympathoadrenal pathway

Answer 9

follows intersomitic BVs around and btwn somites

Question 10

ventrolateral pathway

Answer 10

neural crest cells enter and pass thru ant sclerotome compartments

repulsed from post by semphorinA3F and neuropilin2

passage is facilitated by thrombospondin

Question 11

dorsolateral pathway

Answer 11

migrate just beneath ectoderm

Question 12

sympathoadrenal lineage

Answer 12

cells that take this pathway give rise to:
adrenal chromaffin cells
adrenergic sympathetic neurons
cholinergic sympathetic neurons

Question 13

ventrolateral path lineage

Answer 13

or sensory lineage
give rise to:
dorsal root ganglia
schwann cells

Question 14

dorsolateral path lineage

Answer 14

or melanocyte lineage
give rise to:
melanocytes

Question 15

cranial neural crest cells: R1 - R7 and pharyngeal arches

Answer 15

R1-2 — arch 1
do not require hox influence

R4 — arch 2
require hoxa2 to keep from becoming 1st arch

R6-7 — arch 3
requires hox3

Question 16

circumpharyngeal neural crest

Answer 16

arises from somites 1-7

cells migrate to provide pathway for CN XII

Question 17

cardiac neural crest

Answer 17

arises from somites 1-3

cells migrate towards heart and give rise to:
septa, leaflets of valves, thymus, thyroid, parathyroid

Question 18

vagal neural crest

Answer 18

arises from circumpharyngeal crest

mostly associated w/ gut enteric system but also:
dorsal root ganglia
sympathetic ganglia

Question 19

what role do slit-2 and robo play?

Answer 19

slit 2 expressed near gut and prevents neurons from crossing midline of CNS

trunk neural crest express robo and avoid cells expressing slit-2

vagal crest cells do not express robo thus are able to cross to the gut wall

Question 20

waardenburg’s syndrome

Answer 20

pax3 mutations

white stripe in hair
deaf, cleft lip, eye problems

Question 21

CHARGE

Answer 21

mutation of CHD7 gene

• -deficient in migration of cervical neural crest cells
• -deficient mesoderm formation
• -defective interaction btwn neural crest and mesoderm

Question 22

DiGeorge syndrome

Answer 22

deletion in chr 22

related to defects in neural crest associated w/ 3rd and 4th pharyngeal arches

Question 23

define ectodermal placodes

Answer 23

local thickening in the embryonic ectodermal layer that generally constitutes a primordial group of cells from which a sense organ or ganglion will develop

Question 24

list the major ectodermal placodes

Answer 24

hypophyseal 
olfactory
lens
trigeminal
otic
epibranchial

Question 25

optic stalk

Answer 25

a lateral evagination of the diencephalon which enlarges distally to form the optic vesicle

Question 26

Pax6

Answer 26

expressed in lens, nasal placodes, diencephalon

absence of gene results in early optic vesicle but the rest of the eye doesn’t form

Question 27

____ is necessary for corneal induction

Answer 27

pax6

Question 28

____ stimulated by _____ is necessary for the differentiation of the pigmented retina

Answer 28

otx2 stimed by shh

Question 29

fixation of retinal polarity

Answer 29

nasotemporal or ant-post axis is fixed 1st
—established by gradients composed of ephrins and receptors

dorsoventral axis is fixed 2nd

• –established by actions of shh and BMP antagonistically
• –also ventropin, tbx5, pax2, vax2