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