Centriole Orientation During Left/Right Symmetry in Mice

描述(申请人提供)：发育生物学中一个尚未解决的主要问题是生物体如何沿左右身体轴打破对称性。在小鼠体内，这一过程涉及到在胚胎结节上产生向左流动的液体。这种节流是由节细胞上的纤毛产生的，也可能是被感觉到的。纤毛如何知道向哪个方向驱动液体？理论计算以及研究人员初步的实验流体力学研究表明，如果纤毛向后倾斜，它们可能会向左流动。初步的扫描电子显微镜分析证实，结节纤毛存在这样的后倾。然而，这种倾斜相对于前后轴是如何对齐的？纤毛指向的方向完全由产生纤毛的中心粒决定。研究人员建议通过检查产生结节纤毛的中心粒的取向来确定纤毛后倾斜的基础。他们会问，中心粒取向的哪个方面会随着前后轴的提示而改变。作为这项分析的一部分，研究人员将测试节点中心粒是否像流体传感机械传感模型所预测的那样相对于中线旋转定向。综上所述，拟议的实验将检验中心粒是连接左右轴与前后轴和背腹轴的关键结构的假设。如果研究人员在左右确定的过程中发现中心粒确实是相对于身体轴定向的，这将为未来的实验提供基础，以确定产生这种确定的定向的细胞极性路径和细胞骨架元素。

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.