Paris/Cell auto

From 2007.igem.org

(Difference between revisions)
(Hypotheses)
(Hypotheses)
Line 13: Line 13:
= Hypotheses =
= Hypotheses =
-
We work with a '''constant population''' (no death and no division), we can imagine that we are a stationary phase or between to division cycle.<br>
+
The chosen approach consists in observing the DAP diffusion and differentiation frontwaves. In order to focus on these phenomenon, we work on a ''constant'' population (no death, no division). So we assume that without DAP in its surrounding, a germ cell does not die but remain in passive state (we can imagine that they are at a stationary phase or between to division cycle). It will seem that DAP ''wake up'' bacteria but it's just an artifact due to this assumption.
-
'''Without DAP a cell can't do anything''', so  it seems that DAP ''wake up'' bacteria but it's just an artifact.<br>
+
 
-
The differentiation is '''DAP dependent''', it's append when the cell as enough DAP to evolve but not enough to divide.<br>
+
It may happen that a germ cell as enough DAP to evolve (typically when it is touched by a DAP diffusion front) but we assume that the contribution is not enough for the cell to divide.
-
The '''DAP is made in bacteria S''', the production rate is the difference between the total production and self consummation<br>
+
 
-
The DAP can be under two types intra/extra cellular (DAPi/DAPe)<br>
+
Finally, we assume then that DAP is produced in somatic cells only and consumed by germ cells. The communication is done by distinguishing in the automaton intra and extra cellular DAP (respectively named DAPi and DAPe).
-
The '''DAP is consumed in bacteria G''' <br><br><br>
+
='''''We have 3 bags and 2 entities in our model'''''=
='''''We have 3 bags and 2 entities in our model'''''=

Revision as of 16:25, 25 October 2007



In this part of our work, we aim at characterizing the diffusion of the DAP and the effect on the cells differentiation. This study consists in observing by simulation, the diffusion of DAP in a lawn of germ cells with some isolated somatic cells using a cellular automaton.


Contents

Introduction

DAP feeding between somatic and germ cells is based on an indirect communication process: soma cells produce DAP and release it in the environment; DAP molecules freely diffuse outside until they are captured by a germ cell. We are interesting here in the case where the differentiation of a germ into a soma is DAP dependent. In order to figure out the relation between DAP diffusion and differentiation we propose a simple cellular automaton on square grid. Each cell of the automaton contains a bacterium. We first detail some hypotheses used in this model, then we specify the local behavior rules following by each automaton cell. Finally, the generated simulation is presented.

Hypotheses

The chosen approach consists in observing the DAP diffusion and differentiation frontwaves. In order to focus on these phenomenon, we work on a constant population (no death, no division). So we assume that without DAP in its surrounding, a germ cell does not die but remain in passive state (we can imagine that they are at a stationary phase or between to division cycle). It will seem that DAP wake up bacteria but it's just an artifact due to this assumption.

It may happen that a germ cell as enough DAP to evolve (typically when it is touched by a DAP diffusion front) but we assume that the contribution is not enough for the cell to divide.

Finally, we assume then that DAP is produced in somatic cells only and consumed by germ cells. The communication is done by distinguishing in the automaton intra and extra cellular DAP (respectively named DAPi and DAPe).

We have 3 bags and 2 entities in our model

  • bag

Bact it has a concentration internal of DAP (DAPi) and external (DAPe). It's a cell in our automaton
BactS is a Bact which produce DAPi
BactG is a Bact which consume DAPi

  • entity

DAPi internal value of DAP
DAPe external value of DAP


We produce this set of rules


For bactS

*DAPe = DAPe + DAPe_diffused_in_neighborhood + DAPi_diffused_from_the_BactS
*DAPi= DAPi +DAPi_produced - DAPi_diffused_from_the_BactS


For BactG

*DAPe=DAPe + DAPe_diffused_in_neighborhood - DAPi_diffused_from_the_BactG
*DAPi= DAPi -DAPi_consummate + DAPi_diffused_from_the_BactG
*BactG = if minimal DAPi for differentiation < DAPi < maximal DAPi for differentiation BactS else stay BactG




Initial state


We use a 30x30 cells automaton. All cells are BactG excepted 4 BactS which are placed randomly on the automaton


Parameters


We have 8 parameters and we can add noise for each of them.
In BactS:

  • Dap export
  • Dap import
  • Dap production


In BactG:

  • Dap export
  • Dap import
  • Dap consummation
  • Minimal Dap needed for differentiation
  • Maximal Dap needed for differentiation




Output


We use gbview to generate those pictures

The output is two animated pictures one show the differentiation the other the diffusion of DAPe

Dap diffusionBact differentiation

  • The first picture show the diffusion of DAP
We can see a front wave in light blue after that there is a dark blue area in which the systeme is stable the concentration doesn't evolve.


  • The second picture show the differentiation
Red BactG
Green BactS
The differentiation follow the wave front



In reality this phenomenon does not exist, but this model show that the low concentration of DAP induces differentiation (cells become green)(dark blue),then with high concentration of DAP, the differentiation is inhibited. That why some cells stay in red
We can also note that the population can be stabilized, and the level of DAP remains constant in these areas, the color of the cells doesn't change anymore and the concentration of DAP doesn't change too.

After playing with the parameters, we can deduct 2 important things:

  • The inhibition most be strong and effective (we play with the minimal and maximal value of DAP for differentiation)
if it isn't the case the system collapse all the bactG stay BactG if the inhibition is too strong or switch to BactS if the inhibition is not enough strong.
  • The production and diffusion of DAP will be a critical factor
The DAP has to be produce then he will be exported, it will diffuse in the medium and will be imported
There is no proof of a special system to import or export DAP, so for each step there is a large amount of DAP lost.

Sources