lecture 7 Jan27 pdf - BIOL 303 Developmental Biology...

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BIOL 303 - Developmental Biology Mechanisms of differentiation: Induction & competence Model system – C. elegans vulval development 1. C. elegans as a model system 2. Lin-3/Let-23: induction of VPCs by AC 3. Lateral inhibition by Notch signaling 4. AC/VU decision: another case of Notch signaling
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C. elegans vulva 2nd larval instar - L2 4th larval instar – L4 P3p-P8p are the Vulva Precursor Cells (VPCs) Central part of vulva Lateral vulval cells Lateral vulval cells Fuse into hypodermis Fuse into hypodermis
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What phenotypes to expect? mutants that disrupted vulva formation: 1) No vulva : worms hatch inside (yuck!!) 1) Too many vulvas: formation of ectopic (non functional) vulvas “bag of worms” multivulva From Kornfeld, 1997 vul, egl, lin muv, lin
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C. elegans vulva Identified lin-3 mutant: “bag of worms” 3° cell 3° cell 3° cell 3° cell 3° cell no vulva VPCs Horvitz and Sulston, 1980; Ferguson and Horvitz, 1985; Ferguson et al., 1987
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WT AC VCPs Normal vulva lin-3 AC VCPs “bag of worms” AC: lin-3 VPCs: WT AC (WT) VCPs (lin-3) Normal vulva AC VCPs “bag of worms” AC: WT VPCs: lin-3 Q : Where does LIN-3 act? Experiment: genetic mosaic analysis Results: Interpretation: LIN-3 acts in the AC Gonzalez-Serricchio and Sternberg, 2006
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C. elegans vulva LIN3 (EGF) LET23 LET60 LIN45 Egl-17 = Receptor Tyrosine Kinase = EGF (Lin-3)
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How to iden*fy more players in that pathway? - Screen for mutants with similar or opposite phenotypes Do genetic analysis with them: cross them together, look for synthetic interactions LET-23 LET-60 - suppressor/enhancer screens Fwd genetics: Rev genetics: - Many potential candidates from the RTK pathway LIN-45
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C. elegans vulva Lin-3 AC VPCs How does Lin-3 induce 3 different fates in equally competent VPCs?
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