Critical Timing without a Timer for Embryonic Development.
Timing of embryonic development is precisely controlled, but the mechanisms underlying biological timers are still unclear. Here, a validated model for timing under control of Sonic Hedgehog is revisited and generalized to an arbitrary number of genes. The developmental dynamics where a temporal sequence of gene expression recapitulates a steady-state spatial pattern can be realized through a simple network close to criticality, controlled by the duration of exposure to a morphogen. Criticality simultaneously accounts for many observed biological properties, such as timing, multistability, and canalization of genetic expression. This process can be parsimoniously generalized in many dimensions with a minimum number of genes, all repressing each other with asymmetrical strengths, which also explains sequential activation of different fates. Separation of timescales allows for a simple analytical interpretation. Finally, it is shown that even in the presence of noise, coupling between cells preserves criticality and robust patterning. The model offers a simple theoretical framework for the study of emergent developmental timers.
Ernest Rutherford Physics Building, McGill University, Montreal, Quebec, Canada.
Daniel E
DE
Tufcea
Ernest Rutherford Physics Building, McGill University, Montreal, Quebec, Canada. Electronic address: paulf@physics.mcgill.ca.
Paul
P
François
D000465:Algorithms; D000818:Animals; D003198:Computer Simulation; D047108:Embryonic Development / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D053823:Hedgehog Proteins / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D012249:Rhombencephalon / Q000196:embryology / Q000378:metabolism; D012984:Software; D013269:Stochastic Processes; D013995:Time; D014741:Video Recording
D053823:Hedgehog Proteins