4-1-13_frogs_pt_3

Gilbert 9e fig 79 marginal zone morphogenesis is

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Unformatted text preview: und yolk plug. Gilbert, 9e, Fig. 7.9 Marginal zone morphogenesis is crucial for gastrulation Marginal zone adapted from Gilbert, 9e, Fig. 7.6 The marginal has two cell types: (1) deep cells and (2) superficial cells. The superficial cells of the marginal zone form endoderm. The deep cells form mesoderm. Superficial and deep cells have different fates in Xenopus Marginal zone superficial cells: endoderm Marginal zone deep cells: mesoderm Dorsal marginal zone mesoderm = Organizer Gilbert, 9e, Fig. 7.5 Amphibians- Fate Map (Surface) dorsal AP ventral anterior NIMZ IMZ courtesy Ray Keller VP BCs posterior Amphibians: Fate Map (Surface) • NIMZ = Non-involuting marginal zone. Dorsal NIMZ becomes neural ectoderm; ventral NIMZ becomes epidermis. • IMZ = Involuting marginal zone. Deep cells of the dorsal IMZ are Organizer mesoderm; superficial dorsal IMZ becomes part of the roof of the archenteron. • BC = Bottle cells. They constrict at the beginning of gastrulation, and later respread to form part of the roof of the archenteron. Amphibians- Fate Map (Interior) dorsal NIMZ ventral animal cap anterior blastocoel IMZ (deep) A BCs LEM (deep zone) vegetal base blastopore posterior courtesy Ray Keller Amphibians: Fate Map (Interior) • Deep cells of the dorsal IMZ are Organizer mesoderm. • Dorsal leading edge mesoderm (LEM) becomes head and other mesenchyme. • BC = Bottle cells form part of the roof of the archenteron (A). Amphibians: Deep Cell Fates dorsal dorsal IMZ IMZ ventral anterior LEM ventral DIMZ LEM posterior Hd Ht LV LEM courtesy Ray Keller Amphibians: Deep Cell Fates •Deep cells of the dorsal IMZ are Organizer mesoderm. •Dorsal leading edge mesoderm (LEM) becomes mesenchyme. It forms head (Hd), heart (Ht) and liver (Lv). Gastrulation involves region-specific behaviors Adapted from Gilbert 9e, Fig. 7.10 Gastrulation involves region-specific behaviors Animal cap cells: epiboly via radial intercalation of deep cells and spreading of superficial cells Radial intercalation involves intercalation of cells throughout the thickness of a tissue, leading to its thinning....
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