SLIDE 1
OUTLINE
ÿRegularity vs. Perdiodicity ÿModeling Mechanisms
- Positional Information
- Rearrangement
- Cell lineage
MODELING EMBRYONIC PERIODICITY by Jasmine Hamdan Based on Models - - PowerPoint PPT Presentation
MODELING EMBRYONIC PERIODICITY by Jasmine Hamdan Based on Models - - PowerPoint PPT Presentation
MODELING EMBRYONIC PERIODICITY by Jasmine Hamdan Based on Models for Embryonic Periodicity by L.I. Held, Jr. OUTLINE Regularity vs. Perdiodicity Modeling Mechanisms Positional Information Rearrangement Cell lineage
SLIDE 2
SLIDE 3
REGULARITY – THE FRENCH FLAG PROBLEM
SLIDE 4
PERIODICITY – THE AMERICAN FLAG PROBLEM
SLIDE 5
MODELING MECHANISMS
I. Position Dependent Mechanisms (p -> s) II. Rearrangement Mechanisms (s -> p)
- III. Cell-Lineage Mechanisms (x -> p,s)
SLIDE 6
POSITION DEPENDENT MECHANISMS
ÿ Characteristics
- position of cell determines its state
ÿ Subclasses
- Positional information subclass
- Prepattern subclass
- Determination wave subclass
- Darwinian subclass
(p -> s)
SLIDE 7
Positional Information Subclass ÿ Characteristics
- coordinates interpreted as states
ÿModel Types
- Gradient Model
- Polar Coordinate Model
- Progress Zone Model
ÿ Example
- manifestation of segmentation genes in
Drosophila embryos
- chick wing development
SLIDE 8
Gradient Model
SLIDE 9
Prepattern Subclass
ÿ Characteristics
- mechanical or chemical signals induce state
- cells of adjacent layer induce state
ÿ Model Types
- Physical Force Model
- Reaction Diffusion Model
- Induction Model
ÿExample
- hair follicles in tiger embryo
- bird feathers and mammalian hair
SLIDE 10
Periodic Buckling
SLIDE 11
Wave Determination Subclass
ÿ Characteristics
- traversal of substance determines state
ÿ Model Types
- Chemical Wave Model
- Sequential Induction Model
- Clock and Wavefront Model
ÿ Example
- cAMP in aggregation of slime mold amoeba
- wing coloration of flour moth (Ephestia Kuhniella)
SLIDE 12
Oscillator Model
SLIDE 13
Darwinian Subclass ÿ Characteristics
- selection among competing variants
ÿ Model Types
- Cell Death Model
- State Change Model
ÿ Example
- rows of lepidoteran wing scales
SLIDE 14
State Change Model
SLIDE 15
REARRANGEMENT MECHANISMS
ÿ Characteristics
- state determines cell position
ÿ Model Types
- Adhesion Model
- Repulsion Model
- Interdigitation Model
- Chemotaxis Model
ÿ Example
- somata of motorneurons in zebra fish
- photoreceptors in the Drosophila embryo
(s -> p)
SLIDE 16
Interdigitation
SLIDE 17
CELL-LINEAGE MECHANISMS
ÿ Characteristics
- cell division determines both position and state
ÿ Model Types
- Quantal Mitosis Model
- Stem Cell Model
- Cortical Inheritance Model
ÿ Example
- leech and earthworm embryos
- cilia in protistans
(x -> p,s)
SLIDE 18
Stem Cell Model
SLIDE 19
“Something of the use and beauty of mathematics I think I am able to understand. I know that in the study
- f material things number, order, and position are the
threefold clue to exact knowledge: and that these three, in the mathematician’s hands, furnish the first outlines for a sketch of the Universe.”
- D’arcy Thompson -