Download Cell and Embryology Textbook: Wolpert L, Beddington R, Jessell T

2010/10/1
Cell and Embryology
Textbook: Wolpert L, Beddington R, Jessell T, Lawrence P, Meyerowitz E, Smith
J. (2007) Principles of Development. 3th ed. London: Oxford university press.
Gilbert SF. (2003) Development Biology. 7th ed. Sunderland: Sinaure
Associates Inc.
Schedule
introduction
Basic concept
Exam I
Fertilization
Exam II
Model systems
Exam III
Patterning the vertebrate body plan I: Axes and germ layer
Exam VI
Patterning the vertebrate body plan II: the mesoderm and early
nervous
Exam V
Development of nematodes, fish, sea urchins ascidians and slime
mold
Exam VI
Human embryology or development biology
Final exam VII
http://www2.nsysu.edu.tw/MR-embryology/index.htm
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• development
Why Study Development?
I am fearfully and wonderfully made. (Psalm 139)
There are a Handful of Major Model Organisms
Overview of basic embryonic development
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Zebrafish (Danio
(Danio rerio)
rerio) -- A Vertebrate Model
Zebrafish as a High-throughput Model for biomedical Research and
Therapeutic Development
•It is 3 cm long
•Short generation time
•Large clutch size
Forward Genetics:
ENU mutagenesis
Insertional mutagenesis
•External fertilization
Large number of offspring
Optically clear embryos
Short generation time
S ll Si
Small
Size
Reverse Genetics:
Transgenic fish
Tilling with ENU
Morpholino injection
•Transparent embryos
•Rapid development
Small Molecule
Screens:
Predictive of higher
vertebrates
Delivery by injection
or soaking
http://zfin.org/ and
http://www.nih.gov/science/models/zebrafish/
Carcinogenesis:
Aqueous delivery
Similar to human
tumors
Model organism
cleavage
The organism chosen for understand broad biological principles is
called a model organism.
ARABIDOPSIS THAMAN
MUS MUSCULUS
DROSOPHILA MELANOGASTER
(COMMON WALL CRES
(MOUSE)
(FRUIT FLY)
CAENORHABDITIS ELEGANS
(NEMATODE)
Genomics:
Sequenced Genome
cDNA projects
Microarrays
DANIO RERIO
(ZEBRAFISH)










once fertilization is
completed, a succession
of rapid cleavage
ensues
the cells undergo the
1) S (DNA synthesis)
2) M (mitosis) phases
of the cell cycle
but often no
G1 and G2 phases
No human,
why?
0.25 mm
Figure 21.2
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cleavage in echinoderm embryo
Cleavage to neurulation
the embryo does not enlarge during this period but simply partitions the
cytoplasm of the zygote into many smaller cells, called blastomeres
and each with its own nucleus
Gastrulation: External view
Gastrulation: Internal view
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Caenorhabditis elegans
Xenopus
Drosophila
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Experimental Approaches
• What causes cell differentiation: cytoplasm or nucleus?
•
•
•
•
– Defect experiment:
Defect experiments
Isolation experiments
Recombination experiments
Transplantation experiments
Spemann and Mangold’s Discovery of Induction (1924)
Isolation experiment
Conditional specification?
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after fertilization, embryonic development proceeds through
cleavage, gastrulation, and organogenesis
• Many different structures
– Are derived from the three embryonic
y
germ
g
layers
y
during
g
organogenesis
ECTODERM
• Epidermis of skin and its
derivatives (including sweat
glands, hair follicles)
• Epithelial lining of mouth
and rectum
• Sense receptors in
epidermis
• Cornea and lens of eye
• Nervous system
• Adrenal medulla
• Tooth enamel
• Epithelium or pineal and
pituitary glands
MESODERM
• Notochord
• Skeletal system
• Muscular system
• Muscular layer of
stomach, intestine, etc.
• Excretory system
• Circulatory and lymphatic
systems
• Reproductive system
(except germ cells)
• Dermis of skin
• Lining of body cavity
• Adrenal cortex
ENDODERM
• Epithelial lining of
digestive tract
• Epithelial lining of
respiratory system
• Lining of urethra, urinary
bladder, and reproductive
system
• Liver
• Pancreas
• Thymus
• Thyroid and parathyroid
glands
Figure 47.16
fertilization in sea urchin model
fertilization in sea urchin model
fig 47.3
cortical reaction: sperm
binding activate a signal
transduction pathway
involving 2 second
messengers, IP3 and
d
DAG, that
cause Ca2+ to be released
from the egg’s
endoplasmic reticulum
(ER) into the cytosol  a
surge in Ca2+ levels in
the cytoplasm
fig 11.12
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fertilization in sea urchin model
fertilization in sea urchin model
  cortical reaction: the Ca2+ release from the ER begins at the
site of sperm entry and then propagates in a wave across the
fertilized egg
fig 47.5
fig 47.4
cleavage in echinoderm embryo
cleavage
once fertilization is
completed, a succession of rapid cleavage
ensues
 the cells undergo the
 1) S (DNA synthesis)
 2) M (mitosis) phases
 of the cell cycle
 but often no
 G1 and G2 phases
fig 47.7
the embryo does not enlarge during this period but simply partitions the
cytoplasm of the zygote into many smaller cells, called blastomeres
and each with its own nucleus
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cleavage in frog embryo
cleavage in frog embryo
 morula: the first 5 to 7 divisions form
a cluster of embryonic cells
 blastocoel
 a fluid-filled cavity of the early
embryobegins to form within the
morula and is fully formed in the
blastula
 blastula: a hollow ball of embryonic
cells
 the body axes has been determined
before fertilization and been
i t
intensively
i l studies
t di iin many ffrog spp
polarity of the zygote
 except the egg of mammals, the
eggs and zygotes of animals have a
definite polarity
 is due to uneven distributions of
mRNAs, proteins, and yolk
cleavage in bird embryo
cleavage in bird embryo
fig 47.10
meroblastic cleavage: the incomplete
division of a yolk-rich egg, i.e. cleavage of
the fertilized egg is restricted to the
small disk of yolk-free
yolk free cytoplasm and
cannot penetrate through the dense yolk
 the yolk remains uncleaved
holoblastic cleavage: the complete division
of eggs having little yolk (as in sea urchins)
or a moderate amount of yolk (as in frogs)
blastoderm
the avian equivalent of the blastula
blastomeres devidedinto 2 layers
1)) epiblast: upper
2) hypoblast: lower
blastocoel
the cavity between
epiblast and
hypoblast layers
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gastrulation in sea urchin embryo
gastrulation






gastrula: some of the cells at or near the surface of the blastula
move to an interior location and the embryo becomes 3-germ-layer
embryo
 allows cells to interact with each other in new ways
 ectoderm: forms the outer layer of the gastrula
 endoderm: the embryonic digestive tract
 mesoderm: partly fills the space between the ectoderm and
the endoderm
eventually, these 3 cell layers develop into all the tissues and organs
of the adult animal
gastrulation in frog embryo
gastrulation in bird embryo
• 
•
involution: a process along
the blastopore, future endoderm
and mesoderm cells on the
surface
f
rollll over th
the edge
d off th
the
lip into the interior of the embryo
 blastocoel collapses and
displaced by archenteron which
is formed by the tube of
endoderm
fig 47.12
47 12
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organogenesis in frog embryo
organogenesis in frog embryo

somites: condensations occur
in strips of mesoderm lateral to the
notochord, which separate into
blocks off somites, being arranged
serially on both sides along the
notochord

 parts of the somites dissociate
into individual mesenchymal
cells, which migrate to new
locations

 vertebrae:
t b
th notochord
the
t h d
functions as a core around
mesodermal cells
fig 47.14
organizer region
inductive signals and the cell fate
fig 47.25
Spemann
and
Mangold
g
in 1920s
dorsal lip of the blastopore
functions as an organizer by
initiating a chain of inductions
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formation of the limb in chick model
formation of the limb in chick model
 fig
47.27
homeotic genes and pattern formation
  homeotic genes and pattern formation in the development of the
body segments of Drosophila and Mus
organogenesis
  adult derivatives of the three embryonic germ layers in vertebrates
fig 47.16
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cytoskeleton in morphogenesis
tab 6.1
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