Shams Daniel P, Yang Xingbo, Mehta Pankaj, Schwab David J
Interdisciplinary Biological Sciences, Northwestern University, Evanston, Illinois 60201, USA.
Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev E. 2020 Jun;101(6-1):062410. doi: 10.1103/PhysRevE.101.062410.
The social amoeba Dictyostelium discoideum performs chemotaxis under starvation conditions, aggregating towards clusters of cells following waves of the signaling molecule cAMP. Cells sense extracellular cAMP and produce internal caches of cAMP to be released, relaying the signal. These events lead to traveling waves of cAMP washing over the population of cells. While much research has been performed to understand the functioning of the chemotaxis network in D. discoideum, limited work has been done to link the operation of the signal relay network with the chemotaxis network to provide a holistic view of the system. We take inspiration from D. discoideum and propose a model that directly links the relaying of a chemical message to the directional sensing of that signal. Utilizing an excitable dynamical systems model that has been previously validated experimentally, we show that it is possible to have both signal amplification and perfect adaptation in a single module. We show that noise plays a vital role in chemotaxing to static gradients, where stochastic tunneling of transient bursts biases the system towards accurate gradient sensing. Moreover, this model also automatically matches its internal time scale of adaptation to the naturally occurring periodicity of the traveling chemical waves generated in the population. Numerical simulations were performed to study the qualitative phenomenology of the system and explore how the system responds to diverse dynamic spatiotemporal stimuli. Finally, we address dynamical instabilities that impede chemotactic ability in a continuum version of the model.
社会性变形虫盘基网柄菌在饥饿条件下进行趋化作用，随着信号分子环磷酸腺苷（cAMP）的波动向细胞簇聚集。细胞感知细胞外的cAMP并产生内部cAMP储备以便释放，从而传递信号。这些事件导致cAMP的行波在细胞群体上冲刷而过。虽然已经开展了大量研究来了解盘基网柄菌趋化网络的功能，但将信号中继网络的运作与趋化网络联系起来以提供该系统整体视图的工作做得还很有限。我们从盘基网柄菌中获得灵感，提出了一个将化学信息的中继与该信号的方向感知直接联系起来的模型。利用一个先前已通过实验验证的可激发动态系统模型，我们表明在单个模块中可以同时实现信号放大和完美适应。我们表明噪声在对静态梯度的趋化作用中起着至关重要的作用，其中瞬态爆发的随机隧穿使系统偏向于准确的梯度感知。此外，该模型还能自动将其内部适应时间尺度与群体中产生的行波化学波的自然周期性相匹配。进行了数值模拟以研究该系统的定性现象学，并探索该系统如何响应各种动态时空刺激。最后，我们解决了在该模型的连续版本中阻碍趋化能力的动态不稳定性问题。
