Centriole Orientation During Left/Right Symmetry in Mice

描述（由申请人提供）：发育生物学中的一个主要未解决的问题是生物体如何打破沿着左右身体轴的对称性。 在小鼠中，这一过程涉及产生穿过胚胎结的体液流。 这种淋巴结流动是由淋巴结细胞上的纤毛产生的，也可能是被感知的。 纤毛是如何知道液体的流向的呢？ 理论计算以及研究人员的初步实验流体动力学研究表明，如果纤毛向后倾斜，它们可以驱动一个螺旋流。 初步扫描电子显微镜分析证实，这种后倾存在的节点纤毛。 然而，这种倾斜是如何相对于前后轴对齐的？ 纤毛指向的方向完全由产生纤毛的中心粒决定。 研究者建议通过检查产生结节纤毛的中心粒的方向来确定后纤毛倾斜的基础。 他们会问中心粒方向的哪个方面在对前后轴线索的反应中发生了改变。 作为这项分析的一部分，研究人员将测试节点中心粒是否相对于中线旋转定向，如流量传感的机械感觉模型所预测的那样。 综上所述，所提出的实验将验证这样的假设，即中心粒是连接左右轴与前后轴和背腹轴的关键结构。 如果研究人员发现中心粒在左右决定过程中确实相对于身体轴定向，这将为未来的实验提供基础，以确定产生这种定义的方向的细胞极性途径和细胞骨架元素。

DESCRIPTION (provided by applicant): A major unsolved problem in developmental biology is how organisms break symmetry along the left-right body axis. In the mouse, this process involves generation of a leftward fluid flow across the embryonic node. This nodal flow is created, and possibly sensed, by cilia on the node cells. How do the cilia know which way to drive the fluid? Theoretical computations as well as the investigators' preliminary experimental fluid-dynamics studies indicate that cilia could drive a leftward flow if they were tilted to the posterior. Preliminary scanning electron microscopy analysis confirms that such a posterior tilt exists for node cilia. However, how is this tilting aligned relative to the anterior-posterior axis? The direction a cilium points is dictated entirely by the centriole that produces the cilium. The investigators propose to determine the basis of posterior ciliary tilt by examining the orientation of the centrioles which produce the node cilia. They will ask what aspect of centriole orientation is altered in response to anterior-posterior axis cues. As part of this analysis, the investigators will test whether node centrioles are rotationally oriented relative to the midline, as predicted for a mechanosensory model for flow sensing. Taken together, the proposed experiments will test the hypothesis that the centriole is the key structure that links the left-right axis to the anterior-posterior and dorsal-ventral axes. If the investigators find that centrioles are indeed oriented relative to the body axes during left-right determination, this would provide the foundation for future experiments to determine the cell polarity pathways and cytoskeletal elements that produce this defined orientation.