1. Gen features appear prior to spec. features

2. Less gen char. dev from the more gen until most spec appear.

3. Embryos of given species depart from adult stage of lower animals.

4. Early embryo of a higher animal is never like an adult, only embryo

Developmental Dynamics of Cell Specification

(in order)

1. specification - capable of diff. autonomously (reversible)

2. determination - cell fate is fixed and irreversible even if environment is changed

3. differentiation - dev of specialized cells

1. autonomous - positioning of the morph determinants in the cytoplasm. (mosiac dev.)

2. conditional - ability of cells to change their dev fate according to location (regulation)

3. syncytial - spec of body regions by interactions b/t cytoplasmic regions prior to cellularization

1. sperm and egg contribute equally

2. chromosomes carry inherited pontential (determinants)

3. not every determinant inherited by all cells (diff distribution)

4. only cells with all determinants are those destined to b/c germ cells

Weismann 1893

1. Fate mapping

2. 4 Experimental Techniques

1. Defect - (extirpation) - remove parts and see what doesn't form.

2. Isolation - (explantations) 

3. Recombination - (autoplastic) - move parts to another area w/in embryo

4. Transplantation - replace parts of embryos with parts of diff ones. 

When prospective potency and prospective significance are equal what does this mean?

Who defined this?

The cell is specified and determined.

Dreisch, used isolation experiments.

1. Direction and # of cell divisions

2. Cell shape changes

3. Cell movements

4. Cell growth

5. Cell death

6. Changes in cell membrane or secreted products

1. Collagens - glycoprotein, effects cell adhesion

2. Proteoglycans - more carb than protein, carbs are GAGs

Glycosaminoglycan

Linear polysaccharide chains made of repeating disaccardie units containing either glucosamine or galactosamine.

Roles : lubricant, intracellular adhesive, interactions with GF, anti-coagulant, adhesion promotor

beta subunit connects to RGD binding site on fibronectin outside of cell, connects to talin inside of cell, which attaches to actin microfilament.

Known as bridge.

Cell Adhesion Molecules

1. Cadherins 

2. Immunoglobulin superfamily

CAM

The major cell adhesion molecule. Ca dependant. Anchored by cantenins inside cells, bind to actin inside cells. Spacial segregation.

See in blood/brain and blood/testes barriers

CAM

binding domains resemble those of antibodies.

dev of nervous system

1. E-Cadherins - uvomorulin, drive compaction

2. P-cadherins - placental

3. N-cadherins - nueral crest cells

4. R-cadherins - retinal cells

5. B-cadherins - brain cells

6. EP-cadherins - critical for blastomere positioning

7. Protocadherins - lock connections to cytoskelton, seperation of notocord from other mesoderm

Steinburg's 

conditional 

What three adhesive systems are used in adhesion of embryo to placental wall?

Describe.

1. E & P cadherins - primarily expressed in syncytiotrophoblast

2. Integrin receptors - collagen and heparin sulfate

3. Syncytiotrophoblast - glycosyltransferase enzymes, remains adherent b/c no glucose to finish rxn. Doesn't let go

1. Chemotaxis - cell follows chemical gradient (sperm and egg)

2. Hapotaxis - follows chemical concentration gradient on a substrate. ex. fibronectin

3. Galvanotaxis - follow electirical gradient (nuerons)

4. Contact guidance and inhibition - doesn't stop moving until locked in by other cells.

monoclonal antibodies

lectins

western blot

The ultimate test would be to remove the nucleus of a ____ ______ ____ and transfer to an enucleated egg. Result must be a fully differentiated _____  ______ _______ developed from the egg.

fully-differentiated cell

adult reproductive organism

Yanagimachi

(mice)

light - euchromatin - activity transcribing

dark - heterochromatin - not transcribing

How can you control gene expression?

(4)

1. differential gene transcription

2. selective mRNA processing - remove introns

3. selective mRNA translation 

4. post-translational modifications - insulin, trypsin, folding of proteins.

Irradiating mealy bugs.

Males don't get active chromosome from dad. When only female exposed there were many deaths. When males exposed only females died. 

Drosophila DSCAM

38,000 different proteins possible

How can you control gene expression?

(3)

1. differential mRNA 1/2 life

2. Selective inhibition of translation

3. Cytoplasmic localization (bicoid and nanos)

Dependant in part on length of poly a tail and product presence, both alter the half life. Length is regulated by 3' UTR sequence.

short tail - short half-life

Masked message in the oocytes.

Sans methylation (no cap) or biding of inhibitory proteins.

Poly a tails (short, no translation, but not degraded) (drosophilia bicoid RNA)

3'UTR of bicoid mRNA allows attachment to microtubules, stabilizes position in anterior, dependant on two necessary proteins.

3' UTR of nanos mRNA allows transport to posterior pole via microtubules - bound in posterior by association with other cytoskeletal elements.

Folding patterns - tertiary structure

Address in cell - membranes, compartments (oxidative enzymes of mitochondria)

Alteration of protein chain (removal of AA's) pro-insulin and trypsinogen

Assembly - hemoglobin

Ionic requirements - Ca, phosphate

What is cellular competance?

Name a competancy factor.

ability of cell to respond to a specific inductive signal.

Pax-6

Instuctive interaction/informative - nec for gene inducing new gene

Permissive interaction/environmental - only needs correct environment to express potentials.

Regional specificity - instructive orgin of the organ based on the position of the inducer

Genetic specificity - genome limits extent of response to regional specificity

1. Fibroblast growth factor

2. Hedgehog family

3. WNT family

TGF-B superfamily

angiogenesis, mesoderm formation, axon text.

functions through tyrosine kinase receptors

• found in nearly all mammals
• patterning dorsal portion of somites polarity of limbs, urogenital dev and stem cell proliferation.
• cysteine-rich glycoproteins

Generally have to mature peptide at carboxy terminal end of processed peptide.

May dimerize to themselves (hemodimers) or to other TGF-B peptides (heterodimers)

The __________ family is a member of the TGF-B superfamily.

BMP 

bone formation, cell division, apoptosis, cell migration, differentation.

Regulated by AA's