Chapter 13- The neural crest

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Chapter 13- The neural crest
Recall lineages
Ectoderm-skin/nerves
Mesoderm-Blood, heart, kidney, bones
Endoderm- Gut and associated organs
Recall- Ectoderm has three fates
___________(skin)
1._________
____________________________
2.Neural crest cells
3. _________
__________________
Fig. 12.3
This process is called ______________
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Neural crest cell fate depends largely on where
they _______
The neural crest is a ________ structure
Potential cell fates include- 1. _______ and
_______ 2. ________ of adrenal gland (produces
___________) 3. ______________ cells of
epidermis 4. Skeletal/connective tissue of
___________
Neural crest- four functional ____________
A. ___________- cartilage, bone, neurons, glia of
face
B. __________
C. ________- parasympathetic ganglia
D. ________- melanocytes (produce pigment)
sensory and sympathetic neurons, medulla
Fig. 13.1
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Sensory pathways- conduct info to brain-, spinal
cord
A quick review of nerve nomenclature
1. _____________ nervous system

• ____________ controlled muscles-
• CNS sends signals to _______ muscles of heart,
  blood vessels, iris, pancreas liver, digestive
  tract, kidney
• 1.___________- -homeostasis of body systems,
  originate from hindbrain
• 2. ___________- fright and flight reactions-
  originate form spinal chord

2. ______ nervous system-
-__________ controlled organs- - CNS sends
signals to ________ muscles communication between
various parts of the body (e.g. thallumus,
cerebellum) with muscles
Figure not in text
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A. Start with the _____Neural crest
Two major paths taken
Fig. 13.2
Path 2-cells to _____ of __________ and through
anterior sclerotome to become sympathetic and
sensory ________
Note Sclerotome will become vertebral cartilage
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How do these neural crest cells know where to
migrate?
1. Epidermis secrete ____________________ -
BMP-4 and 7 induce neural crest cells to
produce slug and RhoB
- Slug dissociates cell-cell tight junctions
2. ____________ expression is also lost then
regained once reaching final destination
3. __________ proteins in extracellular matrix
guide cells

• Neural crest cells have Eph ___________
• Trunk sclerotome express Eph ________
• Binding of Eph receptor to Eph ligand
  interferes with migration
• Thus, Eph proteins tell neural crest cells where
  _____ to go

Fig. 13.4
4. __________ factor allows continued
proliferation
5. Other chemotactic and maintenance factors
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• Trunk neural crest cells are __________ (can
  become many cell types)
• However, it may be that only certain populations
  of cells are pluripotent

• Some _________________ have been identified that
  dictate cell fate

Trunk neural crest cell
___________ recently shown to convert neural
crest cells to sensory neurons in mice

• Expose cells to Wnt1 - cells become sensory
  neurons
• If do same experiment in B-cat -/- mice- no
  effect

Lee et al, Science 303, 1020-1023 (Feb. 2004)
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Final cell fate is determined by final
______________
__________ Neuron
Fig. 13.6- Fate of a trunk neural crest cell is
influenced by _____ and ______________
FGF2
Glucocorticoids
Neural crest Cell
__________ Cell
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B. The _________ neural crest
Like the trunk neural crest cells, these can
produce glia, ________ and _____________
But, only __________ neural crest cells can
produce cartilage and bone

• Recall the neural tube subdivides into
  forebrain, midbrain and hindbrain
• The hind brain then further subdivides into
  ________________
• Each rhombomere is a __________, each produces
  ganglia, but each has a distinct _____
• Rhombomeres sit behind the ________________

Pharyngeal arches
Fig. 13.1
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Three paths for ________ neural crest cells
1. Rhombomere ____- to 1st Ph. Arch
1
2. Rhombo. _- to 2nd Ph. Arch
2
3
4
Fig. 13.7
Rhombomeres _______ do not migrate through arches
Fate map of pharyngial arches contributions to
face formation
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What determines distinct fates of cranial neural
crest cells?
Answer- The combination of ______ genes
Evidence
1. _______ KO- neural crest cells of 2nd Ph. Arch
transformed into ___ Ph. Arch structures
2. Hoxa-1 and Hoxb-1 double KO- no _____________
migration
3. Retinoic acid induces more ______ expression
of certain Hox genes- Induces rhombomeres 2 and
3 to assume role of rhombomeres _________
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How is neuronal ______ achieved??
5 ways-
1. Blocking ____ signal allows formation of
dorsal neural tube (recall chapter 12)
2. __________ specifies _______ fate (not
epidermal or glial)
3. Initial __________ determines neuronal type
4. Migration ___________ further dictates
specificity
5. Specific _________ made with target organs or
other neurons
3 parts described
1. __________ selection- axons travel along a
given route
2. __________ selection- axons reach a target,
then bind to specific cells
3. _________ selection- axons now refine
interactions- bind to only a subset of possible
targets
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A. 5 Hypotheses for pathway selection-

• _____________- Growth cone can adhere to certain
  cells, but not
• others

• ________ a glycoprotein which appears to pave
  the road for several axonal migrations

• ________

2. _______________- Growth cone can adhere to
certain cells, but not others
3. ____________ hypothesis- in ______, a neuron
can precisely follow the path of a prior
neuron
Kallmann syndrome- an infertile man with lack of
smell Reason- a single protein directs migration
of both __________ axons and _______________
nerve cells

• 4. ___________-
• _______ (recall Fig 13.4) Growth cones contain
  Eph _______- binding prevents migration into
  undesirable areas
• ___________ proteins- important in directing axon
  turns

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Hypotheses for pathway selection- (Cont.)
5. _______________-
a. ____________ are chemotactic

• Netrins are homologues of the ____________ in C.
  Elegans

Loss of Unc-6 prevents migration of both sensory
(to ventral) and motor (to dorsal) neurons
b. _______________ are repulsive
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B. Hypotheses for_________ selection-
Target cells secrete short-range chemotactic or
_____________ factors
Example- NT-3 attracts axons
C. Hypotheses for _______ selection-
Fig. 13.24
Growth cone makes contact with a cell,
______________ receptors cluster on target cell
surface, and a ______ is formed
Additional axons synapse target cell, but
eventually only _________ remains
Fig. 13.25