Transcript BIO 127 * Developmental Biology Fall 2010

BIO 127 – Developmental Biology
Fall 2011
Dr. Tom Landerholm
[email protected]
Humboldt Hall 211E
916-278-6152
Office Hours: Wednesday 1:00-2:00,
Thursday 2:00-4:00 (or by appointment)
Course Organization
•
•
•
•
•
Section I: Developmental Terms and Processes
Section II: Early Development
Section III: Development of Organ Systems I
Section IV: Development of Organ Systems II
Section V: Late Development and Other Topics
• Labs are designed as extensions of the lectures
– Exams will cover both together as a unit
Grades will be based on the result of four exams, 8 laboratory
write-ups, the presentation of your poster and participation in
the lab as follows:
A(-) > 90%, B(+) > 80%, C(+) > 70%, D(+) > 60%, and F < 60%
Exam 1
Friday 09/16
100 points
Exam 2
Friday 10/07
100 points
Exam 3
Friday 10/28
100 points
Exam 4
Friday 11/18
100 points
Exam 5
Wed. 12/14
100 points
Lab Write-ups 8 total
Project presentation 12/09
200 points
50 points
Total Points 750
Bio 127 - Section I
Developmental Terms and Processes
The Big Picture
Developmental Anatomy
Gilbert 9e – Chapter 1
What are we studying?
• The COMPLEX PROCESS: one cell to one hundred
trillion cells, over 200 cell phenotypes in humans
• The KEY BIOLOGICAL TRANSITION: genetic
inheritance to phenotypic expression
• The SPECIES COMPARISON: all early animal
embryos are similar, the earlier the mutation the
bigger the potential change
A VERY COMPLEX PROCESS
• Most fields of Biology study the adult
– Anatomy, Physiology, Genetics, Molecular Biology
• One cell to one hundred trillion cells
– very tightly regulated cell division and death
• Devo produces 200+ cell types in humans
– nearly every one has the same genotype
– how do they express different genes so they can change?
• Cells, tissues, organs, systems, regulation???
Some of the key terms of Developmental Biology
The three embryonic germ layers
Just a few of the 200+ cell types......
Fig. 13-6
Sexual Life Cycles
Key
Haploid (n)
n
Gametes
n
Mitosis
n
n
Spores
Zygote
Diploid
multicellular
organism
Animals
2n
Mitosis
Mitosis
n
Mitosis
n
n
MEIOSIS
2n
Mitosis
n
n
FERTILIZATION
MEIOSIS
Haploid unicellular or
multicellular organism
Haploid multicellular organism
(gametophyte)
Diploid (2n)
n
n
n
Gametes
Gametes
FERTILIZATION
MEIOSIS
2n
Diploid
multicellular
organism
(sporophyte)
2n
Zygote
Mitosis
Plants and some algae
FERTILIZATION
2n
Zygote
Most fungi and
some protists
n
THE KEY BIOLOGICAL TRANSITION
• Genetic inheritance to phenotypic expression
– XX = female adult, XY = male adult (in some organisms)
– Globin genes carry mutation for sickle cell
– Gigantism can be caused by mutations in a-subunit of G-protein Gs9
• Developmental Biologist wants to know.....
–
–
–
–
What’s on the X and Y chromosome?
When is it expressed? How does it change sex?
Why are globin genes expressed only in RBC? Why does it persist?
a-subunit of G-protein Gs9 - how does that cause large size?
THE SPECIES COMPARISON
• Much is learned from studying
organisms that develop the same way,
as well as those that do it differently
Such as...
• All early animal embryos are similar
• The earlier a mutation, or other event,
occurs, the bigger the potential change
Figure 1.10 Similarities and differences among
vertebrate embryos during development
Sometimes the adults are quite different but the
embryos give away the closeness of two species
Figure 1.19 Homologies of structure among human
arm, seal forelimb, bird wing, and bat wing
Some more key ideas
• Developmental Mechanisms of
Regeneration
• Development’s Role in Evolution
• The Impact of the Environment on
Developing Organisms
Bio 127 - Section I
Introduction to Developmental Biology
Developmental Anatomy
Gilbert 9e – Chapter 1
Fertilization
embryogenesis
Birthing (hatching)
post-embryonic development
Maturity
gametogenesis
Fertilization
post-embryonic devo
and senescence
Death
Birthing (hatching)
The frog is a classic model organism
Frog Post-Embryonic
Development is very
different from ours
animal
vegetal
FERTILIZATION
Figure 1.2 Early development of the frog Xenopus laevis
EGG = GAMETE
CLEAVAGE
BLASTULATION
The result is
a “blastula”
GASTRULATION FORMS THE GERM LAYERS
“gastrula”
neurulation
marks the
beginning of
organogenesis
“neurula”
ORGANOGENESIS
the tadpole
is a “larva”
POST-EMBRYONIC DEVELOPMENT: METAMORPHOSIS
Figure 1.4 Metamorphosis of the frog
Fig. 13-5
Egg
Haploid
gametes
The Human Life Cycle
Sperm
MEIOSIS
FERTILIZATION
Diploid
Zygote
Multicellular
adults
-Embryogenesis
-Post-Embryonic Development
-Senescence
1672
ART AND
ANATOMY
ARE THE
BACKBONE OF
UNDERSTANDING
DEVELOPMENT
1908
1817
1981
The greatest progressive minds
of embryology have not looked
for hypotheses; they have
looked at embryos.....
....Jane Oppenheimer
Drawing is still a very important skill in Developmental
Biology but this semester we will employ the digital
technologies that are available to us to generate the
critical visual communications required to learn DB.
- Digital cameras
- Image software
- Google Images
- University websites
- Wikipedia
- Sac CT
• Like all of our sciences, Developmental Biology, had
to wade through a time before we knew about cell
and molecular biology and digital communications.
– No doubt there are other discoveries coming that will
change how we view these processes in the future.
– We’ll study it in the context of what we know now.
(Don’t let that stop you from being
amazed by the genius of Aristotle!)
This class is going to teach you a LOT of terminology!
Let’s start with some Aristotle classics......
Oviparity = hatched from an egg
(birds, amphibians, most reptiles and fish, inverts)
Viviparity = born live
(placental mammals, some fish and reptiles)
Ovoviviparity = born live from eggs hatched in mom (!)
(sharks, some reptiles)
What is the platypus?
Aristotle Plus Modern Biology...
1. everybody’s born from an egg and
2. cleavage is the first developmental stage after
fertilization of that egg, so...
meroblastic cleavage = some of the egg cell divides
to embryo cells, while some just goes for nutrition
holoblastic cleavage = all of the egg cell divides to
cells, some embryonic and some extraembryonic
Remember: The Germ Layers
formed during gastrulation
This is one of the major morphological determinants of taxonomy in Animalia.
Of the nine phyla in the kingdom, 7 are triploblastic and 2 are diploblastic.
The Blastopore
This is another
key taxonomic
determinant:
2 phyla of 9
in Animalia
form the anus
here, the rest
form the
mouth at the
blastopore.
deuterostomes
v.
proteostomes
formed during gastrulation
The Notochord
Only members
of phylum
Chordata make
a notochord.
(of the three
sub-phyla,
only Vertebrata
makes a spine
out of it.)
Evolution of pharyngeal arches in the vertebrate head
early embryo
adult reptile
adult fish
human
This is also a
characteristic
found only in
Chordata.
von Baer’s Laws:
1. The general features of a large group of animals appear
earlier in development than do the specialized features of a
smaller group.
2. Less general characters develop from the more general, until
finally the most specialized appear
3. The embryo of a given species, instead of passing through
the adult stages of lower animals, departs more and more
from them.
4. Therefore, the early embryo of a higher animal is never like a
lower animal, but only like its early embryo.
Keeping Track of Moving Cells in the Embryo
– A key difference between embryos and adults is
cell movement
• Nearly all embryo cells are on the move
• Only limited types of cells move in the adult
- There are two types of moving cells in the embryo
- Epithelial cells adhere to each other, move as a group
- Mesenchymal cells live and move as individuals
Tissue Morphogenesis results from.....
– Direction and number of cell divisions
– Cell shape changes
– Cell movement
– Cell growth
– Cell death
– Changes in the composition of the cell membrane
or secreted products
– Cell differentiation is an obvious omission!
Important Term: Mesenchymal to Epithelial Transition
Important Term: Epithelial to Mesenchymal Transition
Fate Maps: Mapping the Movements of
Cells in the Embryo
The idea is to....
1. Pick a developmental stage and a group of cells
in the embryo that you want to study
2. Find a way to visually distinguish those cells from
all of the rest
3. Find your cells again during and at the end of the
stage and make a map of their fate
Figure 1.11 Fate maps of vertebrates at
the early gastrula stage
The value of
fate mapping
is clear from
this figure,
which shows
the common
organization
of embryos
even when the
shapes differ.
The process has gotten more sophisticated
as our tools have gotten better and better.
1. Direct observation of pigmented cells in the
embryo
2. Marking small groups of cells in the early embryo
with dyes
3. Replacing embryonic cells of one species with
those of another that look different
4. Replacing embryonic cells with those from the
same species carrying transgenes
Fate map of the tunicate embryo
Direct observation of pigmented cells
in the embryo (sea urchin larva)
Vital dye staining of amphibian embryos
The first experimental
fate maps allowed
investigators to put
color wherever and
wherever needed.
Fate mapping using a fluorescent dye
Powerful fluorescent dyes allowed investigators to take their
fate map studies much later into development of the embryo.
Genetic markers as cell lineage tracers
Chick and quail are so similar that
they won’t immunologically reject
the others’ cells plus quail have
very large nucleoli and the cells are
easy to distinguish from chick cells.
Figure 1.16 Chick resulting from transplantation of a trunk neural crest
region from an embryo of a pigmented strain of chickens into the same
region of an embryo of an unpigmented strain
Chick and
quail can
also grow
up with
each
other’s
parts!
Permanent
fate maps!
Fate mapping with transgenic DNA shows that the neural
crest is critical in making the bones of the frog jaw
Now we can
fate map nearly
any embryo, at
nearly any cell
or stage, with
molecular tools.
Evolutionary Developmental Biology (EvoDevo)
Similarities and Differences Between Embryos Can Define
Most Taxonomic and Evolutionary Relationships
• This idea pre-dates Darwin
• A center pin of “Origin of the Species”
• Two things show in the embryo:
– Commonalities show common ancestry
– Modifications show adaptations to environments
• Combined with von Baer:
– Evolutionary modifications of related species
should come later in development than those of
distant species
Homology vs. Analogy
• Homologous structures arise from a common
ancestral structure
• Analogous structures share a common
function that has arisen independently in the
two (or more) organisms
Larval stages reveal the common ancestry of
two crustacean arthropods
Homologies of structure among human arm,
seal forelimb, bird wing, and bat wing
Development of bat and mouse
How does developmental biology contribute to
this evolution?
• Mice, humans and bats all start with two
forelimb bones and five digits with webbing in
between
• Bat wing has more rapid growth rate in finger
cartilage making digits longer
• Bat wing also has a block to cell death in the
webbing making them connected
Analogous Wing Development
Selectable variation through mutations of
genes active during development
How does developmental biology contribute to
this evolution?
• Humans bred the dachsund to go into badger dens
during the hunt
• Unknowingly, we selected for an extra copy of
fibroblast growth factor 4 (Fgf4)
• Fgf4 tells leg cartilage to stop growing and
differentiate into bone
• An independently acquired mutation, a truncated
Fgf5 gene, allows overgrowth of the hair shaft in
long-haired dachsunds
How can these developmental
relationships directly affect us?
• Between 2% and 5% of humans are born with
visible developmental abnormalities
• some are caused by mutations
• some are caused by environmental disruptions of
development
• These abnormalities have provided a great
deal of insight into normal development
Causes of Birth Defects
- Chromosome anomolies
- Single gene defects
- Mitochondrial defects
- Teratogen exposure
Others:
- Imprinting
- Sporadic/field defects
- Multifactorial
- Idiopathic
Chromosomal Anomolies
Trisomy 21
Down’s Syndrome
Single gene mutation
Human syndrome
Mouse model
Piebald
Syndrome:
KIT mutation
reduces cell
division in
neural crest
cells. These
cells give rise
to pigment
cells, ear cells,
gut neurons,
blood cells and
germ cells.
Mitochondrial Defects
Teratogen Exposure
Treatment for Morning Sickness
Thalidomide Syndrome
Susceptibility
Environmental Estrogenic Compounds
Increasingly Common
Indicator Species
Toxic Plants Ingested by the Mother