A circuit model of the temporal pattern generator of Caenorhabditis egg-laying behavior
1 Division of Biology, University of California, San Diego, La Jolla, CA 92093, USA
2 Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
3 Medical Research Council (MRC) Laboratory of Molecular Biology, Cambridge CB2 0QH, UK
4 Groningen Bioinformatics Centre, University of Groningen, 9751 NN Haren, The Netherlands
5 Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK
BMC Systems Biology 2010, 4:81 doi:10.1186/1752-0509-4-81Published: 7 June 2010
Egg-laying behavior in the nematode C. elegans displays a distinct clustered temporal pattern: egg-laying events occur primarily in bursts or active phases, separated by inactive phases during which eggs are retained. The onset of the active phase can be modeled as a Poisson process with a time constant of approximately 20 minutes, while egg-laying events within an active phase occur with a faster time constant of approximately 20 seconds. Here we propose a cellular model for how the temporal pattern of egg-laying might be generated, based on genetic and cell-biological experiments and statistical analyses.
We suggest that the HSN neuron is the executive neuron driving egg-laying events. We propose that the VC neurons act as "single egg counters" that inhibit HSN activity for short periods in response to individual egg-laying events. We further propose that the uv1 neuroendocrine cells are "cluster counters", which inhibit HSN activity for longer periods and are responsible for the time constant of the inactive phase. Together they form an integrated circuit that drives the clustered egg-laying pattern.
The detailed predictions derived from this model can now be tested by straightforward validation experiments.