Slide 1

Early Vertebrate Development Axis Determination Amphibian Early Development: Frog Fish Early Development: Zebra Fish

Slide 2

Heads or Tails? Axis specification Common theme in early development Conserved mechanisms Divergent mechanisms

Slide 3

Early Vertebrate Development: Xenopus

Slide 4

Xenopus: Cleavage Sperm entry point: Dorsal-Ventral (D-V) axis Microtubule array Cortical rotation.

Slide 5

Xenopus: Cleavage Radially Symmetrical; Holoblastic High amount of yolk in vegetal half. Second cleavage before first finishes. Third= equatorial 16-64 cell stage: Morula 128 cell stage: Blastula

Slide 6

Mid-Blastula Transition DNA demethylation H3K4 methylated (trimethylation) transcription activation Ex. Vegetal cells endoderm. Produce paracrine factors that induce mesoderm specification of cells above.

Slide 7

Xenopus: Gastrulation Same goals as other organsims: get cells to appropriate locations! Movements start in Gray Crescent, cells invaginate to form slit-like blastopore.

Slide 8

Xenopus Gastrulation: Involution Vegetal Rotation: Movement of Pharyngeal endoderm above involuting mesoderm. Involuting Marginal Zone (IMZ)

Slide 9

Xenopus: Gastrulation

Slide 10

Xenopus Gastrulation: Convergent extension

Slide 11

Axis specification in Xenopus: Induction Animal-Vegetal axis determines tissue type A-V, D-V, and L-R axis specification is triggered by fertilization Primary embryonic induction. Hans Spemann and Hilde Mangold- The Organizer

Slide 12

Axis Specification in Xenopus: Molecular Mechanism Dorsal Signal: -catenin, Nodal, and Vg1. Bone Morphogenic Proteins (BMPs) noggin chordin follistatin

Slide 13

Regional Neural Induction in Xenopus Head inducer: Wnt inhibitors Cerberus Frzb, Dickkopf Insulin-like Growth factors Trunk patterning: Wnt and Retinoic Acid

Slide 14

Frogs are left handed! Xenopus Nodal related protein (Xnr-1) determines left-right axis Xnr-1 is expressed on Left side. Pitx2 is activated by Xnr-1 and also persists on left side. Injection of Pitx2 on right side alters gut coiling and heart placement.

Slide 15

Early Vertebrate Development: Danio rerio

Slide 16

Danio Gastrulation

Slide 17

Epiboly and beginning formation of notocord

Slide 18

Axis Formation: Danio D-V axis: BMP/Wnt inhibitors regulated by -catenin and Nodal-like proteins. Fish Nieuwkoop center = Organizer.

Slide 19

Danio A-V axis formation

Slide 20

Left-Right Axis formation in Danio

Slide 21

Early Vertebrate Developement

Slide 22

Slide 23

Slide 24

Slide 25

Slide 26

Slide 27

Slide 28

Slide 29

Slide 30

Slide 31

Slide 32