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Zebrafish development
Monday, May 26
Zebrafish An ideal subject for imaging and manipulation.
Very small species of minnow Native to the Ganges region of India Named for distinctive stripes
Zebrafish have been popularized as a model for studying vertebrate development:
Cell biology and development Organ system development Genetic studies Toxicology Environmental biology
Stages of Zebrafish Development
Key:
=Injection stage =Imaging stage
Fertilization
https://www.youtube.com/watch?v=E381CoymOT8
Devo gone wrong!
Blastula Stages
1-cell 2-cell 4-cell 8-cell 32-cell
512-cell 1000-cell
Transcription begins
sphere dome 30% epiboly
4 2/3 hrs
Cleavage in Zebrafish• What kind of cleavage occurs in fish?
Cleavage in Zebrafish
• At the time of the mid-blastula transition three cell populations form:– yolk syncytial layer (YSL)– enveloping layer (EVL)– deep cells
• What is the importance of each?
GASTRULATION is a complex series of cell movements that:
--rearranges cells, giving them new neighbors--results in the formation of 3 GERM LAYERS that will form
the subsequent embryo: ectoderm, endoderm and mesoderm
--forms the main body axes of the embryo (they were specified earlier but not formed)
Animal and vegetal poles
• A blastula embryo is divided into two hemispheres: the animal pole and the vegetal pole.
• The animal pole consists of small cells that divide rapidly, in contrast with the vegetal pole below it. – The animal pole draws its name
from its liveliness relative to the slowly developing vegetal pole
Gastrulation in Fish• How does gastrulation
begin?
Gastrula Stages
50% germ ring shield
75% 90% bud
10 hr
Three germ layers
Side view
top view
Skin & nervous system
Muscle & cardiovascular
Gut and liver
Animal pole
Vegetal pole
ECTODERM----skin, nervous system, neural crest
MESODERM----muscle, bones, blood and vessels, kidney,gonads, connective tissue
ENDODERM----gut, liver, lungs, pancreas
Gastrulation simplified
Involution
Mesoderm & endoderm insideEctoderm outside
Dorsal-VentralSide view
top view
dorsal
dorsal
ventral
ventral
Involuting cell movements during gastrulation
Convergence-Extension
convergence
extension
Axis Formation in Fish
• How has it been demonstrated that the embryonic shield is critical to dorsal-ventral axis formation?
• What structures form from it?
Axis Formation in Fish• How does notocord induce neural structures from
overlying ectoderm?
Axis Formation in Fish• Where is the Nieuwkoop center and how does it
function?
What determines the anterior-posterior axis?
Neurulation
Neural tube (hollow):formed by subsequent closure of neural platein fish it is a rod first, then becomes hollow
Fish1. neural plate forms on dorsal half of epiblast2. cells on both sides of median hinge point grow together3. rounded rod: neural keel
Organogenesis
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