Transcript Chapter 13- The neural crest

The neural crest
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
1._________
2.Neural crest cells
3. _________
Fig. 12.3
___________(skin)
______________
______________
__________________
This process is called ______________
The neural crest
Neural crest cell fate depends largely on where they _______
Potential cell fates include- The neural crest is a ________ structure
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
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
The neural crest
A. Start with the _____Neural crest
Two major paths taken
Path 1-cells travel ______epidermis,
become melanocytes, colonize hair and
skin follicles
Epidermis
__________
__________
_________
Path 2-cells to _____ of __________ and
through anterior sclerotome to become
sympathetic and sensory ________
Fig. 13.2
This is a _______
Note – Sclerotome will become
vertebral cartilage
The neural crest
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
Neural
Crest
cells
Fig. 13.4
Ephrinin sclerotome
4. __________ factor allows continued proliferation
5. Other chemotactic and maintenance factors
The neural crest
•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:
________
Sympathetic and
Trunk neural crest cell ___________ parasympathetic neurons
Sensory neuron
___________ 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)
The neural crest
Final cell fate is
determined by final
______________
__________
Neuron
Fig. 13.6- Fate of a
trunk neural crest
cell is influenced by
_____ and
______________
Neural crest
Cell
__________
Cell
The neural crest
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
Rhombomeres
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
The neural crest
Three paths for ________ neural crest cells:
Pharyngeal
arches
Rhombomeres in
hind brain of
____________
1
1. Rhombomere ____- to 1st Ph. Arch
2
2. Rhombo. _- to 2nd Ph. Arch
Incus, Malleus, jaw cartilege
Stapes, Styloid Process
3
4
3. Rhombo. __ to 3rd and 4th Ph. Arch
Hyoid bone, thyroid cartilage
Fig. 13.7 Rhombomeres _______ do
not migrate through arches
Fate map of pharyngial
arches contributions to
face formation
The neural crest
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
+ retinoic
No ear
WT
acid
3. Retinoic acid induces more
______ expression of certain
Hox genesInduces rhombomeres 2
and 3 to assume role of
rhombomeres _________
Fig. 13.8
How is neuronal ______ achieved??
5 ways1. 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
A. 5 Hypotheses for pathway selection-
1. _____________- 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. ___________a. _______ (recall Fig 13.4) – Growth cones contain Eph
_______- binding prevents migration into undesirable areas
b. ___________ proteins- important in directing axon turns
Hypotheses for pathway selection- (Cont.)
5. _______________a. ____________ are chemotactic
Fig. 13.20
Rat dorsal spine explant
Neuron
Outgrowth
Neutrin producing cell
•Netrins are homologues of the ____________ in C. Elegans
Loss of Unc-6 prevents
migration of both sensory
(to ventral) and motor (to
dorsal) neurons
Fig. 13.21
Sensory Neuron
Motor
WT Neuron
b. _______________ are repulsive
Unc-6 -/-
B. Hypotheses for_________ selection-
0 min
2 min
Target cells secrete short-range
chemotactic or _____________
factors
Example- NT-3 attracts axons
C. Hypotheses for _______ selection-
Fig. 13.25
Growth cone
makes contact
with a cell,
______________
receptors cluster
on target cell
surface, and a
______ is formed
6 min
10 min
Fig. 13.24
Additional axons synapse
target cell, but eventually
only _________ remains