concurrent cell

Petri Net Simulation: C. elegans Vulval Development

Motion picture: vpcdemo.avi [2 min 19 sec, 14 MB]. Watch 1 min to see most important part.

This short demo is a simulation of the C.elegans (certain well-studied worm) developing its vulva (reproductive organ). There are six Vulval Precursor Cells (VPCs), numbered consequtively from P3.p to P8.p. VPCs decide where to create the organ. The cells are separate "processors" and they communicate to take a global decision.

Each cell has to choose its fate: 1, 2 or 3. Those who select 1 or 2 become the vulva and those who select 3 become the skin of the worm. A special cell, the Anchor Cell (AC), comes near the centrally located P6.p and sends signal LIN-3. This induces the fate 1 in P6.p which then sends signals to its sides. The lateral signal results in the fate 2 taken by P5.p and P7.p. The remaining cells do not get any signal and choose the fate 3.

In the clip and the picutres below you see strongly zoomed-out Petri net. Bluish circles are places, for example genes, proteines, complexes. The the bluer the substance the more of it is present. The rectangles are reactions, for exampleactivation, phosphorilation, complex creation. Red reactions are active. Little red moving boxes denote the transfer of substrates or products of reactions. The bigger the box, the bigger the transfer. You should clearly see six identical cells and two components above - the hypothelium (hyp), the basis of the cells, on the left and the Anchor Cell (AC) on the right.


Click to see the signalling scheme

The vulva is created from the cells which receive signals. Light green is the signal inducing the fate 1 and darker green is the lateral signal inducing fate 2.

Motion picture: vpcdemo-5 [3 min 19 sec, 20 MB]. Watch 2 min to see most important part.

In case the genes were not produced normally, many other possible patterns of fates can occur, such as no vulva or multiple vulvas. An interesting experiment is the knockout of lin-15 gene. In this setting all cells receive LIN-3 (AC signal) also from their environment. The resulting pattern is unstable (1\2, 1\2, 2, 1, 2, 1\2). The simulation above results in a pattern (2, 1, 2, 1, 2, 1).