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111 Cards in this Set
- Front
- Back
Principal mesoderm territories
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Intermediate Mesoderm
Chordamesoderm Paraxial Mesoderm Lateral Plate |
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Intermediate Mesoderm Derivative
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Kidneys
Gonads |
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Chorda-Mesoderm Derivative
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Notochord
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Paraxial Mesoderm Derivative
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Head and Somite
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Lateral Plate Mesodetm Derivative
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Splanchnic Mesoderm(Outer) Circulatory Mesoderm
Somatic Mesoderm(Inner) body Cavity Extra Embryonic |
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Somite Tissue Derivatives
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MEDSS
Myotome(Skeletal Muscle) Endothelial Dermatome(Dermis, Skeletal Muscle) Sclerotome(cartilage) Syndotome(tendons) |
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chordin
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used to suppress BMP, binds BMP
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Paraxis
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essential for somite formation
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Why are Somites Important to study?
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They are essential in segmenting the body, gives you a foundation for body development
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What happened when adding Noggin near Lateral Mesoderm?
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Ectopic somite formation, infers BMP influence on somite formation
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What did the quail somite transplant experiment show?
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showed predicted boundary was determined
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What signaling pathway is responsible for segmentation of somites?
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Notch, important in generating boundaries
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Notch Signaling
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Juxtacrine Signaling, one cell with delta And cell with notch bind, causing notch tail to be severed by protease. severed tail becomes part of transcription complex
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What happens when delta like 3 is knocked out of mouse embryo?
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Multiple mistakes in somite and rib formation, lethal mutation
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Clock and Wave
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Hairy1 is expressed in waves and are timed to condense and pinch off somites
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lunatic fringe
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regulated by notch, responsible for cells to respond to delta signal, can be used to drive GFP formation that is short lived. enabling to see clock wave.
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Determination Front
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Where FGF and WNT are no longer expressed, critical for specifying boundary formation because notch will remain active
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Ephrin A4
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activated by hairy1, tells neighbring cells to make somite boundary, is expressed in anterior half of somite
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Axin
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inhibits Wnt, part of negative feedbackloop where wnt turns on axin as well as notch, axin inhibits, but fgf is still turning on wnt, so it cycles
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Mesp2 and Lefringe
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part of negative feedback loop that supresses notch
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MET
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Mesenchymal to Epithelium Transition. eph ligand become epitheslium surrounding a mesenchymal center
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What happened when presomitic mesoderm was transplanted to another region?
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determined to be what it would have had it not been removed
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How many HOx clusters do vertebrates have? why?
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4, by coping and evolution overtime
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paralogs
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the genes on the clusters that correspond to one another act similarly, like a1 is similar to b1, c1 and d1
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Hox Code Hypothesis
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if you are a certain type of mesoderm spatially, you are going to express a certain combination of hox genes
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What happens when you knock out hox 10 on mouse embryo(Homeotic Transformation)
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you see the cells that should be lumbar become thoracic, they think they are more anterior
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Retonic Acid responsibility in somites
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It posteriorizes, opposite of homeotic transformation
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Role of Retnoic Acid
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It converts the somite to a more posterior structure
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EMT
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Epithelium to Mesenchyme Transition
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MET
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Mesenchyme to Epithelium Transition
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2 day Somite features
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tight ball but specfied cells with lower left quandrant destined for sclerotome
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3 day somite features
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EMT, more heavily in scelrotome Region, you see it spreading out a bit
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4 day Somite features
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Scelrotome completely mesenchyme
dermamytome differentiates to abaxial, primaxial dermamyotome lips and a central dermatome couch like structure there is also primaxial and abaxial myotome cells fated to muscle, the lips guide |
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late 4 day somite features
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extended couch structure
layers of sclerotome and myoblasts, ypu can see central myotome region in dermatome which give rise later to satelite cells |
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what does tagging Prox1 help us to see?
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Abaxial muscle
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What is the effect of SHH on on Somites?
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Turns on Pax1 gene and differnetiates to sclerotome
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What secretes shh?
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notochord
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What does noggin do? Where is it Somite formation?
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Blocks BMPS, notochord secretes it, protects ventral half from BMP4, secreted by Epidermis
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Nerotrophin3 and Wnt 1
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Secreted by neural tube, and inudces Dermatome formation
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Wnt1, Wnt3a and shh
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Secreted by neural tube and notochord respectively, induces Primaxial Myotome by expressing Myf 5
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Wnt, Bmp4 and FGF5
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Wnt from epidermis, and BMP4, FGF5 from Lateral Plate Mesoderm induce Abaxial Myotome by expressing Pax3 and Myod
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General Steps in Muscle Differentiation
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a) myotome cells differentiate, by wnt, ssh-> myoD Myf5
b) multiply and divide, by FGF for growth c) Multiplicaton stops, cells allign, by myogenin d) myotube formation, cellfusion e) myotube maturation, last myoblasts fuze f) maturation of muscle fiber |
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MRFs
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Myogenic Regulation Factors, organized helix loop helix, with DNA Binding domain
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E-Proteins
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Counterparts to MRFs, also Helix loop helix formation, they dimerize and Activate Genes
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List MRF genes
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Myod, myf5,mrf4 and myogenin
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Knockouts of MRFS
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knock out single genes , there is no muscle defects except with myogenin, which as less muscle than normal, it takes a triple KO in order to have serious defects
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General order of MRF gene action
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myoD and myf5 activate eachother and themselves(positive feedback), These activate MRF4 and shortly after FGF is introduced bringing myogenesis to the multiplication stage,
Once FGF is degraded, MRF4 activate Myogenin, the key component in terminal differentiation of muscle |
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Myostatin
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Regulates Muscle growth by stopping muscle cells form dividing.
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What happens if Myostatin is knocked out?
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Bulk Up
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How is the Myostatin gene knocked out?
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insert Stop codon by changing a base through genetic recombination.
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In the Belgian Blue Cow, how did it lose myostatin?
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Deletion
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What family of proteins is Myostatin a part of?
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TGF B, activates smad 2,3 pathway
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what stage of muscle differentiation is myostatin the most active
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Multiplication stage, puts a break on growth and multiplying
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Scelrotome formation
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forms vertebra from two pieces of adjacent sclerotome regions/cells, this is done because of the nerves growing out if the spine
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What does the scelerotome contribute to besides bone?
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the aorta, syndotome, which forms tendons
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Scleraxis
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gene that forms tendons
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How is the Syndetome induced?
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by the myotome cells with FGF, bringing about scleraxis and ultimately tendons
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Stylopod
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Upper Limb, arm humerus, leg femur
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Zeugopod
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Lower Limb, arm ulna and radius
leg Tibula, fibula |
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AutoPod
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hand/feet metacarpals and digits
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What specifies the position of limbs?
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Hox genes in the lateral plate mesoderm, specifically somatic side,
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which hox genes are responsible for limb position and what happens when knocked out?
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b8, c8, d8. shift in fate towards more anterior. the limb is shifted by one segment
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Apical ectodermal ridge
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leading edge of the Limb bud, a key lining of endothelial cells guiding limb bud development
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Trematode Cysts
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generate extra limbs by going into limb buds and splitting it up
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step 1: Limb Development
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FGF10 is expressed widely in LPM. Wnt8c is then expressed which stabilizes and focuses FGF 10.
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step 2: Limb Development
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FGF10 is fouces in a smaller band on LPM. WNT 2b keeps this area expressing FGF10
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Step 3: Limb Development
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FGF10 induces the ecotderm nearby to produce Wnt3a, which in turns induces FGF 8 which then loops back to LPM promoting FGF10 stabilization.
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Tbx5
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transcription factor expressed in mesoderm of anterior forelimb
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Tbx4
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transcription factor expressed in mesoderm of posterior hindlimb
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which somite is line that determines hind or fore limb in the chicken? What happens when you put bead at this location?
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somite 22
chimera limb is developed |
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What happens when tbx4 is forced in forelimb bud mesoderm?
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convert wing to leg, same thing happens with tbx5 but reverse
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What are the four functional regions of the limb bud?
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1) Apical Ectodermal Ridge(AER)
2) Progress Zone(PZ) 3) Zone of Polarizing Activity(ZPA) 4) Dorsal Ectoderm(DE) |
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What happens with AER is removed or put extra on it?
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Loss stops limb development
Gain duplicates digits |
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What happens when Leg Mesenchyme is transplanted to where arm mesenchyme should be?
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becomes a leg, because it expresses tbx4
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What happens when you replace Leg mesenchyme with nonlimb mesenchyme?
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AER regress and limb development ceases
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Progress Zone(PZ)
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located behind apical ectodermal and receives FGF from AER to continue grow. Proximal and distal growth
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What regulates the length of limb?
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Progress Zone is responsible, age determines what structures to form
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What are two Models for PZ explanation of distal growth?
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1) Cells somehow count how many times it has divided, PZ leaves cells behind that know how long they've been away from the PZ
2) Young Bud determines the tissues early on and expands overtime |
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What are the three models for limb development?
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Process model, cells get left behind
early stage, progression, cell boundaries set early Reaction diffusion |
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How are limb bone elemts patterend?
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paralogous hox genes
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Hox gene limb map
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9+10 sylopod
10+11 zuegopod 11,12,13 Autopod |
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What happens when you Knock out hox 11 in regards to limb development?
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Ulna And radius are mising
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What happens when you Knockout hox 13 in regards to limb development?
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autopod, digit fusion
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hox genes and limb development
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Where Hox genes begin to be expressed and this area grows with the limb bud where the higher hox genes are expressed more distally and lower ones more proximally
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Zone of Polarizing Activity
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Responsible for Anterior/Posterior direction of limb, located at posterior end of limb bud, helps to organize up and down oreintation using shh
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Inactive state of shh pathway
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Patched and Smoothened Proteins in membrane are doing nothing and protease cuts ci/gli in half, this forms a repressor
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active state of shh pathway
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binding of hedgehog to Patched, activates smoothened and inhibits proteases and ci activates genes
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How does the ectopic digits in mouse happen in relation to shh?
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mutation of of enhancer that represses shh in certain areas beocmes an activators
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B-Galactsidase
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reporter gene, was used to see expression of shh
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shh patterning in regards to concentration and time of expression
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Digits 4 and 5 have the most shh exposure, as you go more anterior there is less and less influence
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What protein is repressing anterior digits from forming?
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BMP, it helps to make cells respond to Gli
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What happens when you cut pieces of tissue away from inbetween developing digits?
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fingers develop more anterior, like loss of shh, index finger looks like a thumb, but really is losoig BMP which in turn makes the cells lose competence to respond to ssh
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BMP role in digit formation
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induces apoptosis and increases competence to shh
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How AER and ZPA help each other grow?
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by maintaining FGF4 and FGF8 for the AER and shh for the ZPA
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What does the Dorsal Ectoderm express?
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Wnt7a
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what happens when wnt7a is knocked out?
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ventralization of the dorsal side, ventral on both sides
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Gremlin
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inhibits BMP, duck webbed feet
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What are the four ways to regenerate?
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1) Stem Cell Mediated
2) Epimorphosis 3) Morphallaxis 4)Compensatory Regeneration |
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Stem cell mediated Regeneration
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planaria as an example has stem cells throughout the body and regenerate any part cut off, can be seen by piwi, stem cell marker
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Compensatory Regeneration
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differentiated cells replace themselves by dividing, happens in mammalian liver
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Whats the evidence of blastema knowing position?
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blastema transplant showed it healed the daMAGED PART OF THE DONOR EVEN THOUGH THE RECEIPIENT was cut off at different location
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blastema
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a group of tissue right at cut site,
its guides regeneration |
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Epimorphosis
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cells dedifferentiate, they gain stem cell factors. marker msx1. they proliferate and redifferentiate back to the cell type they were.
regeneration that regrows the missing parts by "filling in" the positional system |
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Morphallaxis
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REajusts positional values then re differentiates
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Stages of limb regeneration
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1) Amputation
2) Healing-epidermis heals 3) Dedifferentiation- blastema forms 4) Cone Stage- dedifferniated cells proliferate 5) Palette Stage-newly created cells that are more proximal begin to redifferentiate, blastema looks like palette 6) Notch Stage-right before digits reform, like a notch/nub 7) Digit Stage |
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Are dedifferentiated cells pluripotent?
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no, they act like stem cells but they are still determined to the tissue they came from
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What role does a nerve play in limb regeneration?
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if you denerve the limb, and then cut it off, the limb won't regenerate, proteins prod1(CD59) and nAG
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nAG
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stimulates regeneration
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prod1 expression
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expressed more proximally in blastema.
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What happens when you add REtnoic acid to balstema?
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blastema will grow as if it was right next to the body, a whole limb, RA is probably playing a role
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i cells
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stem cells for regeneration in hydra
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