Lecture 19 Notes - Vandan Desai BIOL 442Developmental...

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Vandan Desai BIOL 442—Developmental Biology 1 Lecture #19—Dorso-Ventral Pattern Formation in the Drosophila Embryo I. Establishment of Dorsal Nuclear Gradient :: A. Dorso-Ventral Patterning in Drosophila i. From ventral => dorsal :: Mesoderm => Neuroectoderm => Lateral Ectoderm => Dorsal Ectoderm => Amnioserosa Mesoderm : heart, muscle, blood, etc. Neuroectoderm : neural tube; equivalent to ventral cord Lateral and Dorsal : cuticles that form bristles Amnioserosa : extra-embryonic structures not found in adult Dorsal-ventral axes are flipped neural structures are ventral in invertebrates (unlike them being dorsal in vertebrates) ii. How are these different tissues specified?— Involves establishment of a D-V gradient of DORSAL (a transcription factor) nuclear localization during the syncytial blastoderm stage Ventral Nuclei = high levels of DORSAL Dorsal Nuclei = low levels of DORSAL DORSAL starts out uniformly expressed in the cytoplasm throughout the embryo; but, upon activation, it translocates to the nucleus of ventral and ventro-lateral cells only DORSAL specifies ventral cell fates B. How are Dorsal Fates Initially Specified? [Activation of Torpedo in Dorsal ] [Activation of Torpedo (EGF receptor) on dorsal side results in inhibition of pipe synthesis in dorsal , but not in ventral follicle cells] i. The oocyte nucleus travels to the anterior and dorsal side of the oocyte ii. The nucleus synthesizes Gurken RNA, which upon translation , activates the Torpedo receptor in follicle cells iii. Follicle cells in which Torpedo is activated are specified as dorsal
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Vandan Desai BIOL 442—Developmental Biology 2 iv. Synthesis of Pipe protein
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