Download Zebrafish Development - UCONJ 542 DEVELOPMENT

Gastrulation
It is not birth, marriage or death, but gastrulation,
which is truly the most important event in your life
Lewis Wolpert
17 hours in the life of a zebrafish embryo
Blastula Stages
1-cell
2-cell
4-cell
8-cell
32-cell
512-cell
1000-cell
sphere
dome
30% epiboly
Transcription
begins
4 2/3 hrs
Gastrula Stages
50%
germ ring
shield
75%
90%
bud
10 hr
Somitogenesis
3-somite
6-somite
18-somite
26-somite
22 hr
Zebrafish development
Early development
?
Three germ layers
Side view
Animal pole
Skin & nervous system
Muscle & cardiovascular
Gut and liver
Vegetal pole
top view
Gastrulation simplified
Involution
Mesoderm & endoderm inside
Ectoderm outside
Dorsal-Ventral
Side view
ventral
dorsal
ventral
dorsal
top view
Involuting cell movements during gastrulation
Convergence-Extension
convergence
extension
Convergence-Extension
Convergence-extension
Cell fates
dorsal
dorsal
Cross section
Dorsal view
Convergence-extension
Convergence-extension
Convergence-extension cell movements
Slow dorsal
migration
Convergence
Extension
Convergence-extension cell movements
Slow dorsal
migration
Fast dorsal
migration
Convergence
Extension
Convergence-extension cell movements
Slow dorsal
migration
Fast dorsal Packing,
migration inhibition of
protrusions
Convergence
Extension
Convergence-extension cell movements
Slow dorsal
migration
Fast dorsal Packing,
migration inhibition of
protrusions
Convergence
Intercalation
Extension
Convergence-extension cell movements
Summary
Cleavage
Formation of
germ layers
Convergenceextension
Formation of
tissue boundaries
Early Development movies
Histone 2B
GFP
Made RNA
Injected embryos at the 1-cell stage
Imaged with Digital Scanned Laser Light Sheet Fluorescence Microscopy
(capture whole embryo image every 60-90s)
Produced a “digital embryo”
Early Development Movies
512-cell
Divisions symmetric prior to 512-cell
Divisions asymmetric after 512-cell
Radial waves just after 512-cell
Early Development Movies
Animal view
Vegetal view
dorsal
dorsal
dorsal
dorsal
dorsal
dorsal
Early Development Movies
Slow-moving nucleus
Fast moving nucleus
Early Development Movies
dorsal
Early Development Movies
Two major Questions
• How are the germ layers established?
• What determines polarity?
Signaling from the YSL
Nodal mutant
wild-type
sqt;cyc -/No endoderm
No head & trunk mesoderm
Normally ~1550 cells internalize; in MZoep ~60 internalize
Germ layer patterning
YSL signal
Tail mesoderm
Sqt and Cyc
Endoderm
Head and Trunk Mesoderm
Dorsal-ventral patterning
Shield
(Organizer)
Bozozok
The Organizer
Shield
(Organizer)
Bmp promotes ventral fates
Bmp signals promote ventral fates (skin, ventral mesoderm)
and oppose dorsal fates (neural, dorsal mesoderm)
Organizer signals are BMP binding factors:
Noggin, Chordin
Mutants in the dorsal-ventral pathway
Snailhouse (snh)
= bmp7 mutant
Chordino (din)
= chordin mutant
Bmp regulates cell movement
High Bmp
Low Bmp
Summary