Developmental biology

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• Developmental biology
• Definition
• Field of biology that studies how a single cell
  (the fertilized egg) gives rise to a fully grown
  organism.
• Draw out embryonic development from 1-cell stage,
  cleavage, blastula, gastrula, germ layer
  formation, body plan development, neurulation,
  organogenesis
• Why study it (why do people get excited about the
  topic? Complexity, beauty, imaging, relevance
  (human congenital defects, cancer)
• Why have a course in it? (most of what you have
  studied so far has been intracellular biology,
  focusing on molecules and what happens inside
  individual cells one important aspect of biology
  that has not yet been covered is how cells
  communicate with each other, how they form
  multicellular organisms, how cells form different
  tissues, and how these different tissues form
  organs that in turn interact with each other).

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• Questions
• axis determination (AP, DV, LR) Q. how do you
  break the symmetry of the egg? Sperm entry,
  localized determinants
• cell differentiation, cell proliferation, cell
  growth
• cell migration, polarization (symmetric vs
  asymmetric cell division), cell shape (giving
  cells different morphologies, e.g. neurons), cell
  death
• morphogenesis (how cells come together to form
  tissues and how these tissues migrate)
• organogenesis
• timing (biological clock)
• aging
• germ cell development, fertilization
• stem cells (what are they (multipotency, ability
  to self-renew), why did they become so trendy
  (Dolly the sheep, 1997, showed that cloning was
  possible development of human ES cells, 1998))
• regeneration
• evo-devo (a field of biology that compares the
  developmental processes of different animals in
  an attempt to determine the ancestral
  relationship between organisms and how
  developmental processes evolved.)
• Q. How efficient is human development? (talk
  about implantation)

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Human reproduction is an inefficient process
50 of concepti do not implant (implantation 8-10
dpf, Heart beat at 21 dpf). a further 30 die
and abort after implantation.
3-4 of all live births possess a
macroscopically visible congenital defect
(120,000 babies/year in the USA).
1 of all babies are born with a heart defect.
20 of neonatal deaths are caused by congenital
defects (the leading cause of neonatal death in
the USA)
congenital disorders are the cause of 50 of
pediatric admissions in the USA
Developmental defects seen at birth are caused by
defects in the cellular processes of development.
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• Developmental biology
• Model systems
• Worm (C. elegans)
• Fly (Drosophila melanogaster)
• Fish (zebrafish, medaka)
• Mouse
• Xenopus (laevis, tropicalis)
• Chick (Quail)
• Sea urchin (echinoderm), ascidians (ciona
  intestinalis, savigni) (urochordate (tunicate)
  (notochord in larvae), hydra (cnidaria,
  invertebrate), planarians (flatworm), arabidopsis
  (weed) ( other plants), axolotls (and other
  salamanders), chlamydomonas (unicellular green
  alga, protozoan), yeast (?),
• Many systems available which one to use most
  powerful one where you can study your questions
  of interest. (also, many of these model systems
  are used to study processes other than
  developmental biology).

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• Developmental biology
• Tools
• - Forward genetics
• - Reverse genetics (is gene x necessary)
  (mutation, RNAi)
• - Gain-of-function expts (is gene x sufficient)
  (mRNA injections, transgenics various levels of
  sophistication, gal4-uas, temporal and spatial
  control)
• - Where is function of gene x required? Creating
  genetic mosaics (genetic, transplants)
• Imaging (live, gene and protein expression)
• - Experimental embryology (cell or tissue
  ablations, bead implantation, chick-quail
  chimeras)

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• Developmental biology
• Course
• Discussions
• one paper per session
• Proposals where to identify topics?

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C. Elegans (adult 1 mm in length)
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C. Elegans development (embryo about 50 ?m in
length)
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Xenopus laevis
AP
V
D
VP
D
A
P
V
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Early developmental stages of Xenopus laevis
2.5 hpf
5 hpf
10 hpf
3.5 hpf
hpf hours post-fertilization
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Early developmental stages of Xenopus laevis
Cleavage movie
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Developmental stages of Xenopus laevis
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Gastrulation the ultimate cell migration problem
Danilchik movie
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Gastrulation and Neurulation highly
coordinated tissue movements
Keller neurulation movie
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Zebrafish embryonic development
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http//anatomy.ucsf.edu/Pages/devbio/course.htm
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http//www.nature.com/milestones/development/miles
tones/index.html