BIO 127 – D evelopmental Biology Fall 2011

BIO 127 – Developmental BiologyFall 2011

Dr. Tom Landerholmlanderholm@csus.edu

Humboldt Hall 211E916-278-6152

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 pointsExam 2 Friday 10/07 100 pointsExam 3 Friday 10/28 100 pointsExam 4 Friday 11/18 100 pointsExam 5 Wed. 12/14 100 pointsLab Write-ups 8 total 200 pointsProject presentation12/09 50 points

Total Points 750

Bio 127 - Section IDevelopmental Terms and Processes

The Big PictureDevelopmental 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

Key

Haploid (n)Diploid (2n)

n nGametes

nn n

Mitosis

MEIOSIS FERTILIZATION

MEIOSIS

2n 2nZygote2n

MitosisDiploidmulticellularorganism

Animals

Spores

Diploidmulticellularorganism(sporophyte)

Plants and some algae

2n

Mitosis

Gametes

Mitosisn

n n

Zygote

FERTILIZATION

nn

nMitosis

Zygote

Most fungi and some protists

MEIOSIS FERTILIZATION

2n

Gametes

n

n

Mitosis

Haploid multi-cellular organism(gametophyte)

Haploid unicellular ormulticellular organism

Sexual Life Cycles

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 IIntroduction to Developmental Biology

Developmental AnatomyGilbert 9e – Chapter 1

Fertilization

Birthing (hatching)

Maturity

Death

Fertilization

Birthing (hatching)

embryogenesis

post-embryonic development

gametogenesis

post-embryonic devoand senescence

The frog is a classic model organism

Frog Post-Embryonic Development is verydifferent from ours

Figure 1.2 Early development of the frog Xenopus laevis

CLEAVAGE

BLASTULATION

FERTILIZATION

EGG = GAMETEanimal

vegetal

The result isa “blastula”

GASTRULATION FORMS THE GERM LAYERS

ORGANOGENESIS

neurulationmarks thebeginning oforganogenesis

“gastrula”

“neurula”

the tadpole is a “larva”

Figure 1.4 Metamorphosis of the frog POST-EMBRYONIC DEVELOPMENT: METAMORPHOSIS

Fig. 13-5

Haploidgametes

Egg

Sperm

MEIOSIS FERTILIZATION

Multicellularadults

DiploidZygote

The Human Life Cycle

-Embryogenesis-Post-Embryonic Development

-Senescence

ART ANDANATOMYARE THE BACKBONE OFUNDERSTANDINGDEVELOPMENT

The greatest progressive mindsof embryology have not lookedfor hypotheses; they have looked at embryos..... ....Jane Oppenheimer

1672 1908

1817

1981

Drawing is still a very important skill in Developmental Biology but this semester we will employ the digitaltechnologies that are available to us to generate thecritical 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

formed during gastrulation

This is anotherkey taxonomicdeterminant: 2 phyla of 9in Animalia form the anus here, the restform the mouth at theblastopore.

deuterostomesv.

proteostomes

The Notochord

Only membersof phylumChordata makea notochord.

(of the three sub-phyla, only Vertebrata makes a spine out of it.)

Evolution of pharyngeal arches in the vertebrate head

This is also acharacteristicfound only inChordata.

early embryo adult fish

adult reptile human

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 offate mappingis clear from this figure, which showsthe commonorganizationof embryoseven when theshapes differ.

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

The process has gotten more sophisticatedas our tools have gotten better and better.

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 experimentalfate maps allowedinvestigators to putcolor wherever and wherever needed.

Fate mapping using a fluorescent dye

Powerful fluorescent dyes allowed investigators to take theirfate map studies much later into development of the embryo.

Genetic markers as cell lineage tracers

Chick and quail are so similar thatthey won’t immunologically rejectthe others’ cells plus quail havevery large nucleoli and the cells areeasy 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 andquail can also grow up with eachother’sparts!

Permanentfate 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 nearlyany embryo, atnearly any cellor stage, withmolecular 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

• 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

How can these developmental relationships directly affect us?

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

PiebaldSyndrome:KIT mutationreduces celldivision in neural crestcells. These cells give riseto pigmentcells, ear cells,gut neurons,blood cells andgerm cells.

Human syndrome Mouse model

Mitochondrial Defects

Teratogen Exposure

Treatment for Morning SicknessThalidomide Syndrome Susceptibility

Environmental Estrogenic Compounds

Increasingly Common Indicator Species

Toxic Plants Ingested by the Mother