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D V High [Dorsal] Low [Dorsal] No Dorsal Graded Dorsal Concentration Created by Mother Hierarchy of Gene Action in D/V Patterning Mesoderm Genes Neuroectoderm Genes Non-neural Genes D/V GenesBasic Tissue Types Controlled by Embryo
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= Mesoderm= Non-Neural Ectoderm= Neuroectoderm Epidermal Genes Dpp Neuronal Genes AS-C RhoVentral Epidermal Genes Neural Genes Twist Mesodermal Genes Snail Neural Genes Brk, Sog Dorsal Genes
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Dorsal meso neuro epi snail dpp “sog” sog dpp
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dpp versus sog Expression sog dpp
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DA Dorsal Region Cell Inside Outside OnOff Repressor From Mother N Nucleus Regulatory Region Coding Region Nucleus Dorsal or Lateral Region Cell Inside Outside Dpp Receptor Sog Signal Relay OnOff Non-neural genes (e.g. dpp) OnOff Neural genes (e.g. AS-C) dpp mRNA No Dorsal Dpp Protein Dpp versus Sog Function
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Mesodermal Genes Neuronal Genes = Mesoderm= Non-Neural Ectoderm= Neuroectoderm Dpp Sog dpp- versus sog- Mutants X Neuronal Genes Epidermal Genes
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Mesodermal Genes = Mesoderm= Non-Neural Ectoderm= Neuroectoderm dpp- Mutant Neuronal Genes Sog
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dpp- Mutant
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Mesodermal Genes Neuronal Genes = Mesoderm= Non-Neural Ectoderm= Neuroectoderm Dpp Sog sog- Mutant X Neuronal Genes Epidermal Genes
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Mesodermal Genes = Mesoderm= Non-Neural Ectoderm= Neuroectoderm Dpp Neuronal Genes Epidermal Genes sog- Mutant
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The Default State of Ectoderm is Neural
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Sog diffuses and patterns the dorsal region The Players Dpp: A signal that promotes dorsal fates Sog: A secreted inhibitor of Dpp Tolloid = Tld: A protease that cleaves and destroys Sog
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Dorsal Ventral Tld Low BMP Hi BMP BMP Sog Non-neural Ectoderm Amnioserosa Sog diffuses and patterns the dorsal region
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A Sog protein gradient forms dorsally Epi Neuro Meso A P V D sog RNA/ Sog Protein
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Sog protein/dpp RNA Tld limits Sog accumulation dorsally WTDf(tld)
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Sog Creates a BMP activity gradient dorsally SogDpp VD [Sog] 1) A dorsal Sog gradient is created by a ventral source and dorsal sinks for Sog. Relative BMPActivity 2) A reciprocal BMP activity gradient forms. 3) Dorsal region is subdivided into two domains. Non-neural Ectoderm A.S. race
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Dpp diffuses and patterns the ventral region - High levels of Dpp signaling in dorsal cells represses all neural genes - Low levels of Dpp diffuse ventrally - Some neural genes are more sensitive than others to Dpp repression (e.g., ind is more sensitive than msh) - Differential sensitivity to Dpp repression creates pattern in the neural region (the least sensitive gene, msh, can be expressed closest to Dpp source)
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= Mesoderm= Non-Neural Ectoderm= Neuroectoderm High Low None [Dorsal] High Low None Dpp Non-neural genes Neural genes Dorsal Subdivision of the Neuroectoderm Neuronal genes Msh Ind Vnd
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Drosophila Neuroectoderm Mouse Neural Tube Sonic Hh BMPs MsxNkx2.2Gsh Dorsal Dpp ind msh vnd dpp Patterning the Neuroectoderm in Flies and Mice
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ind vnd msh D V Ventral Dominant Repression
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vnd Dpp signaling represses ind more effectively than msh mshind Dpp X ind
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ECT NE MES 1 3 2 BrkDpp st2-brk Dpp signaling represses ind more effectively than msh
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Sog Dpp VD [Sog] [Dpp] Relative BMPActivity 2) A BMP repression gradient forms within the neuroectoderm -> Three rows of neuroblasts. mshindvnd Neuroectoderm 1) A Sog gradient creates an inverse BMP activation gradient dorsally -> Non-neural Ectoderm vs Amnioserosa. Non-neural Ectoderm A.S. race Reciprocal Patterning of the Ectoderm by Sog and Dpp
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BMP signaling in the neuroectoderm of flies and vertebrates
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