Two dimensional pattern formationA synthetic multicellular system for programmed pattern formation

(Nature 2005, 434:1130-1134)

Jingyao Guo

Pattern formation

• A hallmark of coordinated cell behaviour in both single and multicellular organisms.

• Typically involves cell–cell communication and intracellular signal processing.

The ring-like patterns formed by receiver cells based on the chemical gradients of an acyl-homoserine lactone (AHL) signal.

The band-detect multicellular system programs E. coli receiver cells to fluoresce only at intermediate distances from sender cells.

Principle

Inside receiver cells

• b: Plasmid map for senders. • c, d: The high-detect (c) and low-detect (d) plasmids that implement t

he band-detect operation.– The high-detect component determines the AHL threshold above

which GFP expression is muted. – The low-detect component determines the lowest concentration

of AHL that elicits GFP response.

Plasmids

HD1 mutation

HD3 mutation

Simulated and experimental liquid-phase behaviour of high-detect and band-detect networks.

hypersensitive LuxR (HD1)

wild-type LuxR (HD2)

reduced-copy-number plasmid (HD3)

BD1

BD2

BD3

The liquid-phase dosage responses of three HD strains showed inverse correlations to AHL concentrations with different sensitivities.

Experiments

Bullseye pattern as captured with a fluorescence microscope after incubation overnight with senders in the middle of an initially undifferentiated ‘lawn’ of BD2-Red and BD3 cells (b) / BD1 and BD2-Red cells(c).

Experiments

The ring formation activity of BD2 cells over the course of 36 h.

Experiments

• No fluorescence for the first 15 h.

• Low levels of fluorescence emerged about 10 mm from the senders.

• Fluorescence values then increased significantly between 5 and 18 mm from the senders.

• Fluorescence values stabilized after about 32 h, reaching a steady-state maximum at 10 mm.

• No observable shift in the position of high fluorescence over the duration of the experiment.

Experiments

Two simulations of the band-detect network with two different sets of kinetic rates.

• Both show position shift.

• The rate constant for LacI decay has the strongest correlation with fluorescence response times and positional shift.

• The stability of LacI affects how closely GFP expression in the receivers reports on the establishment of the AHL gradient from the senders.

• Before GFP expression can begin, AHL has to activate the production of CI, and LacI levels must subsequently decline.

Form more elaborate patterns by placing multiple sender disks in differentconfigurations.

Experiments

• Naturally occurring developmental processes;

• Tissue engineering;

• Biomaterial fabrication;

• Biosensing .

Significances

Thanks.