Wolpert et al., 1998

1
The main axes of a developing vertebrate embryo
Wolpert et al., 1998
2
Animals share germ layer organization
Wolpert et al., 1998
3
?
4
Embryonic Patterning in Zebrafish
blastoderm
yolk
dorsal
determinants
microtubules
A
Spemann- Mangold Organizer
SMO
bozozok
V
D
Nieuwkoop Center
-catenin
b
YSN
yolk
P
BMP
5
Developmental Biology Toolbox

• Pure Description
• Microscopy, Fate Mapping
• Experimental Methods
• Embryological methods
• Gain of function approaches
• Injections, transgenic methods
• Loss of function approaches
• Forward Genetics
• Reverse Genetics (Knockout, Knockdown)

6
Developmental Biology Model Systems
7
What are important features of an ideal animal
model system?

• Short generation cycle
• Small size of adult animal, but relatively large
  embryos
• Low cost of maintenance
• Mating habits (no seasonal variation)
• Large umber of progeny
• Fast embryogenesis
• Ability to screen for morphological and
  behavioral traits
• Advanced knowledge of embryology and behavior
• Small genome size
• Advanced are genomics
• - genetic map
• - genomic libraries, chips
• - knockout technology
• - transgenesis methods
• - mutagenesis methods
• - genome sequence

8
Cleavage of Xenopus embryo
Cleavage of the zebrafish embryo
Wolpert, Dev. Biol., 1998
9

• Strategy for identification of recessive zygotic
  mutations in zebrafish.
• Upon ENU mutagenesis F2 generation genetic screen
  is performed

10
De Robertis et al., 2000
11
(No Transcript)
12
Fate Map of Frog Pre-Gastrula
Wolpert, Dev. Biol., 1998
13
Frog and Zebrafish Fate Maps are similar
Yolk Cell
Wolpert, Dev. Biol., 1998
14
De Robertis et al., 2000
15
Wolpert, Dev. Biol., 1998
16
Wolpert, Dev. Biol., 1998
17
De Robertis et al., 2000
18

• Injection of synthetic b-catenin RNA into
  zebrafish zygote induces secondary axis

Kim Fekany-Lee
19
blastoderm
yolk
dorsal
determinants
microtubules
Spemann- Mangold Organizer
SMO
bozozok
Nieuwkoop Center
-catenin
b
YSN
yolk
20
bozozok - Japanese motorcycle thug
SMO
NC
Fekany et al., 1999
21

• boz function is required for organizer formation
• boz function in YSL is sufficient for normal
  development

wt
boz
Fekany et al., 1999
22
Fekany et al., 1999
23
(No Transcript)
24
Neural ectoderm
Nonneural ectoderm
SMO
somites
V
D
Bmp
25
(No Transcript)
26
Morphogens are molecules that specify cell fates
directly in a concentration dependent manner
Wolpert et al, 1998
27

• Increased BMP activity phenocopies the boz
  phenotype

BMP
28
boz negatively regulates BMP activity
Bmp
wt
boz
chordino
bmp2b (swirl)
bozozok
boz
wt
chordin
29
Bozozok and Chordin functionally interact to
repress Bmp during head and trunk development
Gonzalez et al., 2000
30
boz din mutants lack head and trunk rudiments
boz din
wt
31

• In boz din double mutants nonneural ectoderm is
  expanded at the expense of neural ectodermal

gta3
10 h
huc
14.5 h
wt
boz din
32

• boz din mutants show a dramatic increase in bmp4
  expression

7.5 h
13 h
boz din
wt
33
(No Transcript)
34
A coinhibition of BMP activity by overlapping
functions of only two genes, bozozok and
chordino, specifies head and trunk during
vertebrate development
BMP