Exam 2: Neural Crest and Facial Disorders Flashcards
Neural crest cells have what 3 characteristics?
transient
migratory
multipotent
Neural crest cells are only found in
vertebrate embryos
neural crest cells important for embryo development, forming __ germ layer
4th germ layer
where are neural crest cells in head/face?
bones.
Pharyngeal arch
cranial morphogenesis
Mesoderm, ectoderm, endoderm, where are neural crest cells from?
Ectoderm, but special. They can turn into anything
How do neural crest cells migrate in the chicken embryo?
Dorsal –> Ventral
back to front
tools for cell fate mapping
1) vital dye labelling
2) lineage tracing
Describe vital dye labeling
using certain dye to label cells on back.
Culture embryos and see where labelled cells go. Then injection shows where cells migrate. Where you inject determines where they migrate.
Neural crest cells migrate based on where they originated.
HOWEVER, injections could be contaminated, need something more precise.
How do you use Cre-Loxp system for lineage trace?
Mate Cre with LacZ and stop allele
Offspring gets lacZ- recognizes certain color. Label cells without taking them out.
What do we see from Wnt1Cre tracing?
migrate extensively and go far.
Wnt1cre to skull
c-shape morphology in E8.5-15, in forebrain, midbrain, medial arch.
To study the origin of the scale: what labels? What results ?
mesp1-cre/R26R- label mesoderm cells
Wnt1-cre/R2R- label neural crest cells
Wnt- frontal
Mes- parietal
Conclusion? Scalp has 2 origins.
Neural crest derivatives
1) PNS
2) Endocrine and paraendocrine derivatives
3) Pigement cells
4) Facial cartilage and bone
5) connective tissue
many very specific cell types
neural crest development- 4 stages
1) Induction
2) Delamination
3) Migration
5) Specification
Induction
transformed from ectoderm into neural crest cell
Delamination
through epithelial-mesenchymal transformation (EMT)
Migration
toward ventral destination
Specification
multipotent neural crest cells differentiate into specific lineages
Where do neural crest cells originate from?
Ectoderm cells at the neural plate border
Edge of neural tube are neural crest cells, follow development from ectoderm to tube
Neural plate inductive signals
Bmps, Wnts, FGFs, Notch
Neural plate border specifiers,
Dll5, Pax3/7
Neural plate crest specifiers
FoxD3, Twist, Snail, Sox10
Neural crest effectors
MlTF, Rho GTPases, Kit, Ret
How do neural crest cells migrate
Dorsal –> Ventral
dorsal ventral pathway
dorsal lateral –> ventral lateral
What are they hypothesis for why D –> V
1) Growth Factor Gradients
2) Fibrolactin
Neural crest cells migration patterns: Cranial cells
Cranial cells spread SHEET (frontonasal prominence cells)
spread in STREMS (pharyngeal arch cells, including cardio and neural crest cells)
Neural crest cell migration patterns:
Trunk cells
dorsal root ganglia
Neural crest cell migration patterns:
Vagal and sacral neural crest cells
adrenal gland
Example of cardiac cells which are in cranial neural crest cells
top part of heart
pulmonary artery, arch, arota
Trunk neural crest cells migrate in 1 of 2 pathways
1) Neurons and glial cells (ventromedial)
2) Melanocytes (dorsolateral)
Dorsolateral: both sides
Ventromedial: into the heart, determine glial cells
Transplantation of trunk neural crest cells
radiolabeled donor chicken embryo.
neural crest cells transplant to another chick embryo.
Cells Black = neural crest
transplant donor –> host (chicken/quail)
4 types of cell neural crest can make
**not: doesn’t mean these cells only from neural crest, just that it CAN make them
1) Mesenchymal (firoblasts, muscle, heart)
2) Neuronal cells
3) Secretory cells (chromaffin, parafollicular, calcitonin producing)
4) pigmented cells (melanocytes)
Specification of neural crest:
Edn1 and Nppc
Cartilage/bone
Specification of neural crest:
Neuregulin and Edn3
Schwann cells
Specification of neural crest:
Neururin, Gdnf, Nts
neurons
Specification of neural crest:
Edn3, alpha-MSH, Steel (steel and Edn3 together)
Melanocytes
Why express each different gene?
lineages in different origins, different segments. Tell morphology under microscope. What makes 1 segment different from the others.
____ is a crucial regulator of neural crest cell differentiation
Sox10
Cranial neural crest cells become…
cartilage/bone
connective tissue
pigment
glial/peripheral neurons
Trunk neural crest cells become…
pigment
glial/peripheral
Vagal and Sacral neural crest cells become…
gut enteric ganglia
how do neural crest genes decide the factor of derivatives?
interact with cofactors
congenital craniofacial disorders
scalps have different patterns. We know the lines connected to different tracks and they have different patterns.
craniofacial anomalies observed in __ human newborns with birth defects
3/4
Occurrence of cleft lip/palate
1:700
Occurrence of cleft craniosynostosis
1:2,500
*****What is craniosynostosis?
premature closure of scalp
bones fuse.
Normally, babies born, scalp has several bones which separate so brain can grow.
Since bones not separated, grow and pressure builds. Effects development/speaking ability.
cleft lip and palate
unilateral and bilateral
severe nose/upper lip split
1/1,000-1/700 world wide.
highest in Asians
Cleft lip/palate (45%), palate (35%), lip (20%)
Causes of cleft lip and palate
genetic factors
environmental factors- mother with alcohol early, cigarette, prenatal nutrition, drug exposure, other environment factors
80%- only lip/palate, probably genetic
mammalian craniofacial morphogenesis
feltro?- place where face fits like puzzle, meets at top line. why faces have nose groove.
Happens in womb between 2-3 months
Upper lip formation in mammals
2 things
mnp and lnp form triangle region.
Two separate regions that fuse for upper lip.
when they get close, ectoderm cells covering migrate and undergo apoptosis. Forms integrated tissues.
*If cells don’t die- cleft lip
What indicates that apoptosis is a pathway for the epithelia seam breaking down during upper lip fusion?
Expression of active Caspase 3 at the boundary between MNP/LNP
___ regulates upper lip fusion via maintaining cell proliferation and activating apoptosis at LNP/MNP boundary.
Lrp6
activating apoptosis at LNP/MNP boundary
if cell does not meet in middle, cleft lip in mouse.
Palatogenesis
formation of secondary palate.
upper lip: MxP and MNP
palate: Mx cells?
critical steps of PALATE development
Growth
Elevation
Adhesion/fusion
Any step disruption = cleft palate
Polarity of developing palate
anterior posterior
Lateral Medial Lateral
Barx1 is only lower part of palate. Certain polarity. Regulated by different genes, which interact and monitor.
Polarity of Developing palate: The anterior palatal shelves elevate in a flip-up process,
flip-up process
Polarity of Developing Palate: the posterior palatal shelves undergo
remodeling and reorientation through horizontal outgrowth from the medial wall
Cellular process for palate fusion
1) apoptosis
2) extrusion of medial edge sema (MES) cells
this is what happens to ectoderm cells, but not in palate. instead, cells attach and migrate to the side (displacement) actin cables left in. Forms epithelial triangle which eventually disappears.
Molecular control palate patterning
takes a number of genes
Epitheial cell development important
cells lose integrity and fuse.
5 categories of palatal shelf defects that result in cleft palate
1) failure of palatal shelf formation
2) fusion with tongue or manidibel
3) failure of palatal shelf elevation
4) failure to meet following elevation
5) persistence of medial edge epithelium
Calvaria development and craniosynostosis
premature suture fusion
1/2,500 births
plagiocephally
20-30%
fused coronal suture
(one side)
Sacphocephaly
40-60%
Fused saggital suture
Trigoncephaly
fused metopic suture
what causes types of craniosynostosis
mutations of Fgf2 cause autoactivation of receptor and abnormal differentiation of suture cells
How do we rescue craniosynostosis mouse.
Fdfr2 mutation is functional mutation. Receptor can be activated without ligand binding.
Erk signal downstream.
Erk signal shows WT mutant rescuing.
calvaria derived from what two origins?
neural crest
mesoderm
Suture cells are ____ cells, which serve as ____
mesenchymal stem cells
serve as connection between different bones
Development of homeostasis of calvaria is under rigorous control of
genetic factors, such as FgFr2
