BIOPHYSICAL MECHANISMS OF CHEMOTAXIS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。趋化性是细胞感知并向高浓度化学物质方向移动的能力，是免疫反应的一个组成部分。此外，它在伤口愈合、血管生成和胚胎发生中起着关键作用。distyostelium disideum是一种社会性变形虫，是真核细胞的模式系统，近二十年来得到了广泛的研究。在我们的实验中，我们通过量化信号转导网络中这一关键组成部分对化学引诱剂重复时空脉冲的定位动力学，来探测和定量测量单个盘状骨细胞的初始趋化反应。我们发现单个细胞的反应在脉冲到脉冲之间是非常可复制的。相比之下，我们观察到细胞间的趋化反应有很大的可变性，即使群体中的不同细胞暴露在相同的脉冲下。虽然平均而言，一群细胞能找到脉冲的正确方向，但在响应的方向和大小上却存在显著的可变性。通过测量cAMP分子的外部浓度，定量地探讨了噪声和细胞个性的来源。我们观察到，定向传感机制的可靠性不受外部cAMP分子数量少的限制，并且当外部cAMP分子增加2个数量级时，噪声并不降低。进一步的研究旨在更好地理解趋化机制，将利用通过软光刻技术生产的微流体装置来产生各种时空化学梯度。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Chemotaxis, the ability of the cell to sense and move in the direction of higher concentration of chemicals, is an integral part of immune response. Additionally it plays a key role in wound healing, angiogenesis, and embryogenesis. Dictyostelium discoideum, a model system for eukaryotic cells, is a social amoeba and has been studied extensively over the past twenty years. In our experiments, we probe and quantitatively measure the initial chemotactic response of single Dictyostelium cells by quantifying the localization dynamics of this key component of signaling transduction network in response to repeated spatio-temporal pulses of chemoattractant. We find that the response of a single cell is very reproducible from pulse-to-pulse. In contrast, we observe a large variability in the chemotactic response from cell-to-cell even when different cells in population are exposed to the same pulse. Although on average a population of cells finds the correct direction of the pulse, a significant variability is observed in the direction and the magnitude of the response. Origins of the noise and cell individuality by quantitatively are explored by measuring the external concentration of the cAMP molecules. We observe that the reliability in the directional sensing mechanism is not limited by the low number of external cAMP molecules and the noise does not decrease when the external cAMP molecules increases by 2 orders of magnitude. Additional studies aimed at better understanding the chemotaxis mechanism will utilize microfluidic devices produced via soft lithography techniques to generate a variety of spatio-temporal chemical gradients.