The Neural Crest the fourth germ layer

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The Neural Crest the fourth germ layer

The Great Wave Off Kanagawa, Katsushika Hokusai
(1760-1849).
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Neural Crest Cells are interesting because they
are

• migratory
• pluripotent

• Facial bones
• Pigment cells of skin
• Sensory ganglia of dorsal root
• Thymus, thyroid, parathyroid

• Major arteries of the heart
• Peripheral glial cells
• Peripheral nerve cells
• Sympathetic (adrenal medulla)
• Parasympathetic (gut peristalsis)

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Chick
Quail

http//www.sdbonline.org/archive/dbcinema/ledouari
n/ledouarin.html
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MELANOCYTES DORSAL ROOT GANGLIA

SYMPATHETIC GANGLIA
GLIAL CELLS
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Important questions about the neural crest

• How is the neural crest induced at the N-E
  boundary?
• What are the A-P differences between NC cells and
  how do these differences arise?
• What are the migratory pathways of NCs?
• Are cells specified before they migrate or after
  they get to their destination?

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Prospective Fate Maps of Blastulae
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Double in situ hybridization in a frog early
neurula for the neural plate gene Sox2 (blue) and
the neural crest gene Slug (purple)
Sox2
Slug
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TF cascade
Neural plate border specifiers
Neural crest specifiers
http//www.anat.ucl.ac.uk/research/mayor/index.htm
l
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Important questions about the neural crest

• How is the neural crest induced at the N-E
  boundary?
• What are the A-P differences between NC cells and
  how do these differences arise?
• What are the migratory pathways of NCs?
• Are cells specified before they migrate or after
  they get to their destination?

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CRANIAL
PHARYNGIAL
CARDIAC
VAGAL
TRUNK
SACRAL
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This chick embryo has been stained with an
antibody (HNK-1) that is used to identify
migrating neural crest cells. The dark blue
regions (arrows) are streams of neural crest
cells. The stream of cells migrate to the
branchial arches (I-!V). Arch I forms the
mandible (lower jaw), Arch II forms the hyoid
apparatus, and neural crest from Arches III and
IV contribute tothe heart. Failure of these
cells to migrate, or to differentiate is thought
to be a common cause of congenital heart
defects. http//web.uvic.ca/rburke/burkelab/
neuralcrest.htm
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Figure adapted from Harvey et al., Heart
Development (1999)
Ablation of the cardiac neural crest in chick
results in patterning defects of the great
arteries, ventricular septal defects, and
abnormal development of the thymus, thyroid and
parathyroid glands.
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Important questions about the neural crest

• How is the neural crest induced at the N-E
  boundary?
• What are the A-P differences between NC cells and
  how do these differences arise?
• What are the migratory pathways of NCs?
• Are cells specified before they migrate or after
  they get to their destination?

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Two pathways (dorsolateral and ventral) for
migration of trunk neural crest cells
http//dir.nhlbi.nih.gov/labs/ldb/chd/neuralcrest.
asp
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Dorsolateral route d/d mutation blocks DL neural
crest migration in salamanders
http//8e.devbio.com/article.php?ch13id132
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Reciprocal transplantation experimenthttp//8e.de
vbio.com/article.php?ch13id132
Conclusion failure to migrate is not due to the
cells, but their environment.
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Ventral route Stain for antibody to HNK-1
protein
ANT
POST
MIGRATION THROUGH ANTERIOR SOMITE ONLY!
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Important questions about the neural crest

• How is the neural crest induced at the N-E
  boundary?
• What are the A-P differences between NC cells and
  how do these differences arise?
• What are the migratory pathways of NCs?
• Are cells specified before they migrate or after
  they get to their destination?

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Le Douarin, N. M., D. Renaud, M.-A. Teillet and
G. H. Le Douarin. 1975. Cholinergic
differentiation of presumptive adrenergic
neuroblasts in interspecific chimeras after
heterotopic transplantation. Proc. Natl. Acad.
Sci. USA 72 728732.
Neural crest donor
host
Conclusion A-P fates are conditionally
specified. Other evidence suggests some limits to
this pluripotency along the A-P axis.
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Single NC cells are pluripotent
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