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Morphogen gradient, cascade, signal transduction

Morphogen gradient, cascade, signal transduction. Maternal effect genes. Zygotic genes Syncytial blastoderm. Cellular blastoderm. Homeotic selector genes Similar signal into different structures— Different interpretation—controlled by Hox genes.

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Morphogen gradient, cascade, signal transduction

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  1. Morphogen gradient, cascade, signal transduction Maternal effect genes Zygotic genes Syncytial blastoderm Cellular blastoderm

  2. Homeotic selector genes Similar signal into different structures— Different interpretation—controlled by Hox genes

  3. Homeotic transformation of the wing and haltere Homeotic genes—mutated into homeosis transformation As positional identity specifiers: Bithorax-haltere into wing

  4. Imaginal discs and adult thoracic appendages Bithorax mutation—Ubx misexpressed T3 into T2 –anterior haltere into Anterior wing Postbithorax muation (pbx)— Regulatory region of the Ubx— Posterior of the haltere into wing

  5. The spatial pattern of expression of genes of the bithorax complex Bithorax—Ultrabithorax –5-12 Abdominal-A—7-13 Abdominal-B—10-13 Bithorax mutant –PS 4 default state +Ubx—5,6 +Abd-A—7,8,9 +Abd-B—10 Combinatorial manner Lack Ubx—5,6 to 4 also 7-14 thorax structure in the abdomen Hox—gap, pair-rule for the first 4 hours, then polycomb (repression), and Trithorax (activation)

  6. Regulatory elements

  7. Segmental identity of imaginal disc Antennapedia—expressed in legs, but not in antenna If in head, antennae into legs Hth (homothorax) and Dll (distal-less)—expressed in antennae and leg In antenna: as selector to specify antenna In leg: antennapedia prevents Hth and Dll acting together Dominant antennapedia mutant (gene on)— blocks Hth and Dll in antennae disc, so leg forms No Hth, antenna into leg

  8. Fly and mouse/human genomes of homeotic genes

  9. Homeobox and homeodomain

  10. Expression pattern and the location on chromosome

  11. Egg chamber formation A/P during oogenesis the oocyte move towards one end in contact with follicle cells. Both the oocyte and the posterior follicle cells express high levels of the E-cadherin If E-cadherin is removed, the oocyte is randomly positioned. Then the oocyte induces surrounding follicle cell to adopt posterior fate.

  12. Specifying the Anterior-Posterior Axis of the Drosophila Embryo During Oogenesis

  13. Specifying the Anterior-Posterior Axis of the Drosophila Embryo During Oogenesis Protein kinase A orients the microtubules

  14. Anterior/posterior extremities Torso---receptor tyrosine kinase Ligand---trunk Terminal structure- acron, telson, most posterior abdominal segment Before fertilization ligand immobilized on vitelline membrane Small quantities—bound to torso at the poles little left to diffuse

  15. Torso signaling Groucho: repressor Huckenbein, tailless are released from transcriptional suppression

  16. The EGFR signal establishes the A/P and D/V axial pattern Gurken—TGFa Torpedo--- EGFR

  17. The EGFR signal establishes the A/P and D/V axial pattern Red-actin Green-gurken protein As well as mRNA The expression of EGFR pathway target gene

  18. The localization of Gurken RNA Cornichon, and Brainiac- Modification and Transportation of the protein K10, Squid localize gurken mRNA (3’UTR& coding region) Cappuccino and Spire – cytoskeleton of the oocyte MAPK pathway

  19. The Key determinant in D/V polarity is pipe mRNA in follicle cells Cross section

  20. The activation of Toll windbeutel—ER protein pipe—heparansulfate 2-o-sulfotransferase (Golgi) nudel—serine protease

  21. The dorsal-ventral pathway Perivitelline space Fig. 31-16

  22. Toll pathway Maternal genes— Fertilization to cellular blastoderm Dorsal system—for ventral structure (mesoderm, neurogenic ectoderm) Toll gene product rescue the defect Toll mutant – dorsalized (no ventral structure) 2. Transfer wt cytoplasm into Toll mutant specify a new dorsal-ventral axis (injection site =ventral side) spatzle (ligand) fragment diffuses throughout the space

  23. The mechanism of localization of dorsal protein to the nucleus Without Toll activation Dorsal + cactus Toll activation – tube (adaptor) and pelle (kinase) Phosphorylate cactus and promote its degradation B cell gene expression Dorsal=NF-kB Cactus=I-kB

  24. Dorsalization mutation

  25. The activation of NF-kB by TNF-a NLS

  26. The dorsal-ventral pathways Fig. 31-17

  27. Dorsal nuclear gradient Activates—twist, snail (ventral) Represses—dpp, zen (dorsal) Fig. 31-19

  28. Toll protein activation results in a gradient of intranuclear dorsal protein Spatzle is processed in the periviteline space after fertilization

  29. Model for the subdivision of the dorso-ventral axis into different regions by the gradient in nuclear dorsal protein Zygotic genes pattern the early embryo Dorsal protein activates twist and snail represses dpp, zen, tolloid Rhomboid----neuroectoderm Repressed by snail (not most ventral) Binding sites for dorsal protein in their regulatory regions

  30. Nuclear gradient in dorsal protein Dorsalized embryo— Dorsal protein is not in nuclei Dpp is everywhere Twist and snail are not expressed Threshold effect—integrating Function of regulatory binding sites Regulatory element =developmental switches High affinity (Dpp) (more dorsal region-low conc.) Low affinity (twist, snail) (ventral side-high conc.)

  31. Snail— Reduce E-cadherin

  32. Microarray analysis for gene expression profile

  33. Dpp protein gradient Cellularization---signal through transmembrane proteins Dpp=BMP-4(TGF-b) Dpp protein levels high, increase dorsal cells Short of gastrulation (sog) prevent the dpp spreading into neuroectoderm Sog is degraded by tolloid (most dorsal)

  34. The TGK-b/Bmp signaling pathway • Antagonist • Proteases dpp: decapentaplegic Smad= Sma + Mad Sma-C. elegans Mad-Fly Fig. 31-24

  35. The Wnt and BMP pathways are used in early development Fig. 31-23

  36. The Smad-dependent pathway activated by TGF-b Type I, II receptor-Ser/Thr phosphorylation

  37. The Smad-dependent pathway activated by TGF-b Colorectal cancer: type II receptor Pancreatic cancers: 50% Smad One component between receptor and gene regulation

  38. De-repression of target genes in Dpp signaling groucho Nature reviews genetics-8-663-2007

  39. Structural and Functional Domains of Smad Family TGFb , Activin: R-Smad 2,3 BMPs: R-Smad 1, 5, 8 Common Smad4-nucleocytoplasmic shuttling, DNA binding Inhibitory Smads: I-Smad 6, 7 Cell, 95,737,1998

  40. Integration of two signal pathways at the promoter Smad2 and FAST Smad3 and c-Jun/cFos Cell,95,737, 1998 SBE: Smad binding element ARE: activin-response element TRE: TPA-response element (AP-1 binding) XBE: transcription X

  41. Smad4 shuttles between the cytosol and nucleus SARA: smad anchor for receptor activation NLS , NES 13,216, 2003

  42. Inhibitory Smads: I-Smad 6, 7 —recruting Smurf (ubiquitin ligase to receptor) Cell, 95,737,1998

  43. Different internalization pathways resulted in distinct cellular effects 2005, 17:107

  44. Models of morphogen gradient formation sharpen Fig. 31-11, 12, 13

  45. The axis determining systems Fig. 31-21

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