chapter 13- the neural crest ectoderm-skin/nerves endoderm- gut and associated organs...

Chapter 13- The neural crest

Ectoderm-skin/nerves

Endoderm- Gut and associated organs

Mesoderm-Blood, heart, kidney, bones

Recall lineages

Recall- Ectoderm has three fates

___________(skin)

__________________

____________________________

2.Neural crest cells

3. _________

1._________

Fig. 12.3 This process is called ______________

The neural crest

Neural crest cell fate depends largely on where they _______

Potential cell fates include-1. _______ and _______2. ________ of adrenal gland (produces ___________)3. ______________ cells of epidermis4. Skeletal/connective tissue of ___________

A. ___________- cartilage, bone, neurons, glia of face

D. ________- melanocytes (produce pigment); sensory and sympathetic neurons, medulla

C. ________- parasympathetic ganglia B. __________

Neural crest- four functional ____________

The neural crest

The neural crest is a ________ structure

Fig. 13.1

A quick review of nerve nomenclature

1. _____________ nervous system

2. ______ nervous system-

Sensory pathways- conduct info to brain-, spinal cord

-“____________ controlled muscles”-- CNS sends signals to _______ muscles of heart, blood vessels, iris, pancreas liver, digestive tract, kidney

1.___________- -homeostasis of body systems, originate from hindbrain2. ___________- fright and flight reactions- originate form spinal chord

Figure not in text

-“__________ controlled organs”- - CNS sends signals to ________ muscles communication between various parts of the body (e.g. thallumus, cerebellum) with muscles

A. Start with the _____Neural crestThe neural crest

Two major paths taken

Epidermis

This is a _______

Path 1-cells travel ______epidermis, become melanocytes, colonize hair and skin follicles

Path 2-cells to _____ of __________ and through anterior sclerotome to become sympathetic and sensory ________ Note – Sclerotome will become

vertebral cartilage

Fig. 13.2

__________

__________

_________

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 destination3. __________ 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 Ephrinin sclerotome

Neural Crest cells

Fig. 13.4

4. __________ factor allows continued proliferation5. Other chemotactic and maintenance factors

The neural crest

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

___________ Sensory neuron

________ Sympathetic and parasympathetic neuronsTrunk neural crest cell

• Some _________________ have been identified that dictate cell fate:

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

Lee et al, Science 303, 1020-1023 (Feb. 2004)

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

The neural crest

Final cell fate is determined by final ______________

Fig. 13.6- Fate of a trunk neural crest cell is influenced by _____ and ______________

__________ Neuron

__________ Cell

Neural crest Cell

FGF2

Glucocorticoids

B. The _________ neural crest 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 ________________

Fig. 13.1Pharyngeal arches

Rhombomeres

Three paths for ________ neural crest cells:

1. Rhombomere ____- to 1st Ph. Arch

Rhombomeres in hind brain of

____________

2. Rhombo. _- to 2nd Ph. Arch

3. Rhombo. __ to 3rd and 4th Ph. Arch

Rhombomeres _______ do not migrate through arches

1

2

3

4

Pharyngeal arches

Fig. 13.7

Fate map of pharyngial arches contributions to face formation

The neural crest

Incus, Malleus, jaw cartilege

Stapes, Styloid Process

Hyoid bone, thyroid cartilage

What determines distinct fates of cranial neural crest cells?

Answer- The combination of ______ genes

1. _______ KO- neural crest cells of 2nd Ph. Arch transformed into ___ Ph. Arch structures

Evidence

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 _________

+ retinoic acidWT

Fig. 13.8

No ear

The neural crest

How is neuronal ______ achieved??

2. __________ specifies _______ fate (not epidermal or glial)

1. Blocking ____ signal allows formation of dorsal neural tube(recall chapter 12)

3. Initial __________ determines neuronal type

4. Migration ___________ further dictates specificity

5. Specific _________ made with target organs or other neurons

3 parts described1. __________ 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

5 ways-

A. 5 Hypotheses for pathway selection-

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

2. _______________- Growth cone can adhere to certain cells, but not others

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

3. ____________ hypothesis- in ______, a neuron can precisely follow the path of a prior neuron

Kallmann syndrome- an infertile man with lack of smellReason- 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 areasb. ___________ proteins- important in directing axon turns

5. _______________- a. ____________ are chemotactic Fig. 13.20

•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

Unc-6 -/-WT

Sensory Neuron

Motor Neuron

b. _______________ are repulsive

Hypotheses for pathway selection- (Cont.)

Neutrin producing cell

Rat dorsal spine explant NeuronOutgrowth

B. Hypotheses for_________ selection-

Target cells secrete short-range chemotactic or _____________ factors

Example- NT-3 attracts axons

0 min 2 min

6 min 10 min

Fig. 13.24C. Hypotheses for _______ selection-

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