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107 Cards in this Set
- Front
- Back
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The AP axis of neural tube is regulated primarily by __ ___.
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Hox genes
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T/F Motor neuron specificity is regulated by the cell's age when it last divides
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T
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A neurons birthday determines which layer of the ___ it will enter.
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cortex
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Motor neurons axons travel from the ___ ___ to a specific ___. In the optic system, axons originating in the retina find their way back into the ____.
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spinal cord; muscle; brain
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The specificity of axonal connections is seen to unfold in what three steps? How are these steps regulated?
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1. Pathway selection
2. Target selection 3. Address selection Chemosensory structures |
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Growth cones detect and respond to molecular ___ ___.
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guidance cues
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Motor neurons can establish their normal patters of innervation in the absence of ___ ___.
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Neuronal activity
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The ECM provides substrates for the ___ ___ to migrate, and these substrates provide ____ info to it.
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growth cone; navigational
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If substrates adhere to growth cone, what happens? What is the other possibility?
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Promotes axon to grow in that direction; can cause growth cone to retract.
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Growth cones require ___ surfaces for migration. These roads have ___ on them.
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adhesive; laminin ("highways")
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Laminin often coats ___ cells. ___ is the receptor required to bind laminin.
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glial; integrin
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What three types of guidance cues can growth cones detect?
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1. ECM
2. Transmembrane proteins 3. Diffusible factors |
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Two of the membrane protein families involved in neural patterning are the ___ and the ___.
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Ephrins and semaphorins
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Contact Dependent repulsion causes growth cone to ___.
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collapse
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Semaphorins often guide growth cones by __ ___.
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selective repulsion
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Membranes isolated from the posterior portion of a somite cause the growth cones of these neurons to ___. Why?
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collapse; These gc's have Eph receptors
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What region of each somite is covered with ephrin? What is repelled by lanes of ephrin?
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posterior; axons
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T/F All semaphorins are membrane bound
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No; Some are diffusible
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Which semaphorin is membrane bound? Diffusible?
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Sem1; Sem2 and Sem 3
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All semaphorins mediate ___.
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Repulsion
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Sem1 inhibits the growth cones of the ___ sensory neurons from moving forward, thus causing them to turn.
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Ti1 (Sem1 is between epithelial cells. Ti1 is searching for Cx1 so Sem1 helps it find it)
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T/F Sem3 patterns sensory projections from the dorsal root ganglia by selectively repelling certain axons so that they terminate dorsally
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T
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T/F growth cone directs growth, not collapse
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T
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Netrins are a chemoattrac./chemorepuls.?
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Chemoattractant. They guide commissural axons across midline
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Commissural neurons are interneurons that cross the ___ midline to coordinate ___ to ___ motor activities.
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ventral; right; left
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Commissural neurons are told by ___ ___ to travel from dorsal to ventral on neural tube.
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diffusible factors
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Commissural neurons are attracted to the ventral region of neural tube by what gradients?
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Shh (from floor plate) and Netrin1 (from floor plate)
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Netrin-1 acts as an ___ and a ___ signal in vertebrates. How?
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Attractive; repulsive; Gc's of retinal neurons are attracted to netrin-1 and are guided to head of optic nerve. Once there, netrin1 and laminin work together to prevent axons from leaving the optic nerve.
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Laminin of ECM surrounding the optic nerve converts the netrin from being an ___ molecule to a ___ one.
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attractive; repulsive
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What do wt unc-6 induce axons from central located sensory neurons to move to? What about ventral located motor neurons?
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ventral; dorsal
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Unc-6 is a homologue to what? What happens in unc-6 mutants?
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Netrin; sensory neurons don't move ventrally and motor neurons don't move dorsally.
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What happens in unc-5 mutants? unc-40?
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motor neurons dont move; sensory neurons don't move
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What mutation led to the discovery of the netrin receptor?
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unc-5
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Slit protein is a chemo_________.
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repellant
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What does Robo do for Slit?
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It is a receptor for slit on growth cones of Drosophila neurons
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Slit is only located in the ____. What does it do?
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midline; Slit prevents most neurons from crossing the midline from either side.
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Along with Slit, what other protein is in the midline? Is it a chemoattractant or chemorepellant?
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Commissurless; Chemoattractant
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What does commissurless do to Robo?
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downregulates it as they approach midline
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Without slit, axons enter midline but they cant do what?
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Leave the midline
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Slit and robo work together with __ and __. This allows ___ neurons to cross the midline.
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DCC and Netrin; commissural
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Robo 3 inhibits robo1 so growth cone can pass through midline with help of what signals?
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DCC and Netrin
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Besides Slit, what else is in the midline that acts as a chemoattractant?
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Commissurless
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Target cells secrete ___, such as ___ ___ ___ ___.
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neurotrophins; Nerve growth factor (NGF), Brain-derived neurotrophic factor (BDNF), and Neurotriphins 3 and 4/5 (NT3, NT4/5)
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T/F Neurotrophins (all 4 examples) can act both to attract the groth of some axons and inhibit other axons
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T
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Neurotrophin receptors are called ___. They are a type of ___.
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Trk; RTK
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When an axon contacts its target it forms a specialized junction called a ___.
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synapse
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What are released at the synapes from the axon terminal?
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Neurotransmitters
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When axons reach the muscle cell, the neuron secretes ___ which causes ___ receptors to cluster near the axon.
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Agrin; ACh (acetylcholine)
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What ECM component connects the axon to the muscle cell?
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beta 2 Laminin
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Soon after the axon joins the muscle cell, ___ begin building up in the axon terminal.
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neurotransmitter-containing vesicles
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When one axon binds, many other bind, but in the end only one axon remains. This is "_____ __"
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Address selection
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Neurotrophins are involved in target selection, but they also help in neuronal ___.
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survival
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What three things help in the survival of a neuron?
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1. neurotrophins
2. ECM 3. depolarization |
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What happens to excess neurons?
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apoptosis
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T/F All neurons respond the same way to all types of neurotrophins
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F
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What is pruning? What happens if it's misregulated?
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When excess neurons die away; Alzheimers
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R-cadherin is involved with?
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The retina
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Directional migration of the retinal ganglion growth cones depends on the ____ -expressing glial endfeet.
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N-CAM
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What three things help in retinal axon migration?
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1. Laminin
2. N-CAM 3. Netrin 1 |
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___ and ___ are very important in retinal layering.
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N-cadherin ; R-cadherin
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What three adhesion molecules help orient the retinal axon to the optic tectum?
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Integrins, NCAM, cadherins
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When mammalian retinal ganglion axons reach the optic ___, they have to decide if they are to continue staight or it they are to turn 90 degrees.
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Chaism
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What repulses some axons from turning right or left when entering the optic chaism?
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ephrin on neurons in chaism and ephrin receptors on retinal axons (dictates ipsilateral or not)
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Temporal axons attach to the ___ side of the tectum, and Nasal axons attach to the ___ of the tectum.
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anterior; posterior
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Neural crest cells migrate and can become what four things?
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1. Neuron and glial cells of sensory system
2. Epinephrine-producing cells of the adrenal gland 3. Pigment-containing cells 4.skeletal and connective tissues in head |
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Laminin is necesarry to keep neurons ___ in optic ___.
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constrained; nerve
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In the kitten experiment, What was lost when one eye was shut in a newborn?
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Transient contact was lost for that eye. Axon dies due to lack of neural activity.
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What happened in the kitten experiment when both eyes were shut?
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No blindness. Neurons can't "out compete eachother"
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What happened in the kitten experiment when 1 eye was shut after it was 3 months old? What did that prove?
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No blindness. There is a critical period when transient contacts are made permanent.
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What is the first thing to happen during specification of the neural crest?
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border gets specified by BMPs and Wnt8 high in lateral low in center..
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BMP and Wnt are where on the developing NC?
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Neural fold
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What are the five regions the crest can be divided into?
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1.Cranial
2. Cardiac 3. Trunk 4. Sacral 5. vagal |
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___ ___ are the ultimate specifiers of AP neural crest fates.
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Hox genes
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How many pathways do trunk neural crest cells have to choose from?
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2
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What do the earliest trunk neural crest cells do? What do they become?
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Migrate ventrally away from neural tube to PNS. They become sensory and sympathetic neurons and Schwann cells.
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T/F Pigment cells from retina come from trunk neural crest cells
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F-all other pigments are
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Trunk cells that migrate second travel along what pathway? What do they become?
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Dorsolateral; Melanocytes (skin)
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What transformation do neural crest cells undergo to separate from the epithelium?
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epithelial-to-mesenchymal
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The epidermis secretes what?
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BMP and Wnt
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When FGF and Wnt are present, ___ induces expression of what proteins in the cells destined to become neural crest?
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BMP; slug and RhoB
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What happens if slug or RhoB is inhibited?
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Crest cells fail to emigrate from the neural tube.
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What does slug do?
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Makes sure adhesion gene isn't transcribed
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What does RhoB do?
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It is a GTPase that regulates actin polymerase
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What happens if you mutate BMP, Wnt, OR FoxD3?
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No neural crest!
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What is FoxD3 used for?
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It specifies premigratory crest
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Schwann cells come from where?
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Ventral route of trunk neural crest cells
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The ventral route of trunk NC cells is controlled by what?
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ECM and chemotactic factors
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What does the ECM contain (surrounding the neural tube)?
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Fibronectin, laminin, some collagens..etc
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What factors impede migration of neural crest cell movement? Where are they located?
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ephrins and semaphorins;Posterior section of each somite (so NC don't go there)
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What is GDNF?
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It's produced by gut mesenchyme and its receptor is RET. Come from NC of sacral and vagal regions. Controls peristalsis.
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T/F Maturation of somites adjacent to Neural tube controls migration of neural crest cells
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T
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What crest cells are attached to the colon?
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Glial-derived neurotrophic factor (GDNF)
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The adrenal gland secretes what two hormones?
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cortisol and epinephrine
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Does ephrin play a positive or negative role in ventral pathway of trunk crest cells? Dorsal pathway?
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negative; positive
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Stem Cell Factor (SCF) is important for what?
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Critical for dorsolateral migration of trunk NC cells. Allows proliferation and antiapoptosis
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What happens if you put SCF somewhere like your foot?
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melanocytes go there!
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Neural crest cells are ___.
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Pluripotent
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SCF is AKA
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steel ligand (mouse)
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Loss of SCF ligand or receptor results in
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same thing. lack pigment..sterile...
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NC cell fates depend on ___ not place of ___.
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eventual location; origin
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The final differentiation of NC cells is determined in large part by ____.
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environment they migrate to
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___ factors encounted in the environment help specify the different neural crest-derived lineages in the trunk.
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Paracrine
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Cranial NC cells are special because they make. What usually makes these tissues?
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Cartilege, bone, muscle; mesoderm
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The jaw bone comes from where?
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Pharyngeal arch bone
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What happens if Hoxa1 and Hoxa2 are knocked out?
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no arch 2 derivatives. r4 makes A2 so you get 2 A1 instead.
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What does RA treatment do to hindbrain?
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POSTERIORIZES
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The heart NC initially forms near r__.
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7
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