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Unformatted text preview: BICD 130 Embryos, Genes, and Development D/V patterning of the neural tube: Signaling molecules Green: Sonic hedgehog Blue: Dorsalin (TGF- family) Red/orange: Motor neurons D/V patterning of the neural tube: Transcription factors Green: Pax6 Blue: Pax7 Red: Nkx6.1 Yellow: Motor neurons Specification of the neural crest by signaling molecules and transcription factors FoxD3: Required for neural crest cell specification Slug: Required for neural crest cell migration Major Divisions of the Neural Crest Cranial (cephalic) Trunk (6 through tail) Vagal (1-7) & Sacral (posterior to 28) Cardiac (1-3) Domains of the neural crest Regional Derivatives of the Neural Crest Cranial: Skeletal and connective tissues of the face and neck; cranial nerves Trunk: Pigment cells; dorsal root (sensory) ganglia; sympathetic ganglia; adrenal medulla Vagal and Sacral: Parasympathetic (enteric) nerves of the gut Cardiac: Connective tissue of large arteries near the heart Hirschsprung Disease: A congenital disorder characterized by absence of enteric ganglia along a variable length of the intestine Normal HD Apparent cause: Failure of neural crest cell migration into the hindgut
Iwashita et al. (2003) Science 301: 972-976 Pluripotency of neural crest cells Growth factors and the fate of neural crest cells e Pathways of neural crest cell migration in the trunk region of the chick embryo Anterior Neural crest cells taking the ventral pathway migrate through the anterior portion of the sclerotome HNK-1 Migrating neural crest cells avoid ephrinexpressing (posterior) regions of the sclerotome
mRNA HNK-1 Repulsion of neural crest cells by posterior Ephrin proteins Ephrins Eph receptors Axon Guidance Molecules Semaphorins (membrane/soluble) Ephrins (membrane) Netrins (soluble) Slits (soluble) Action of Semaphorin I in the developing grasshopper limb Selective inhibition of sensory axon projections by Semaphorin III in the rat spinal cord Selective inhibition of rat mechanoreceptor axons by Semaphorin III-secreting tissue culture cells Ephrin inhibits motor axon outgrowth Ephrins Ephrin inhibits motor axon outgrowth Opposing gradients of Ephrin and Eph receptors pattern chick retinotectal projections Role of netrins in the guidance of commissural axons in the rat spinal cord netrin-1 Attraction and repulsion of axon outgrowth by netrins Control of sensory and motor axon projection by netrin in the worm embryo Dark blue: UNC-6 expression UNC-6: Netrin UNC-5: Component of repulsive receptor UNC-40: Component of attractive receptor Control of commissural axon projection by Slit and Robo in the fly embryo Comm: Attractive cue Slit: Repulsive cue Robo: Slit receptor Commissural axons never leave the midline in Slit mutant embryos all CNS neurons all CNS neurons ...
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