Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, NY 13210, USA.
Dev Biol. 2012 Oct 1;370(1):52-62. doi: 10.1016/j.ydbio.2012.07.019. Epub 2012 Jul 26.
Cilia-generated fluid flow in an 'organ of asymmetry' is critical for establishing the left-right body axis in several vertebrate embryos. However, the cell biology underlying how motile cilia produce coordinated flow and asymmetric signals is not well defined. In the zebrafish organ of asymmetry-called Kupffer's vesicle (KV)-ciliated cells are asymmetrically positioned along the anterior-posterior axis such that more cilia are placed in the anterior region. We previously demonstrated that Rho kinase 2b (Rock2b) is required for anteroposterior asymmetry and fluid flow in KV, but it remained unclear how the distribution of ciliated cells becomes asymmetric during KV development. Here, we identify a morphogenetic process we refer to as 'KV remodeling' that transforms initial symmetry in KV architecture into anteroposterior asymmetry. Live imaging of KV cells revealed region-specific cell shape changes that mediate tight packing of ciliated cells into the anterior pole. Mathematical modeling indicated that different interfacial tensions in anterior and posterior KV cells are involved in KV remodeling. Interfering with non-muscle myosin II (referred to as Myosin II) activity, which modulates cellular interfacial tensions and is regulated by Rock proteins, disrupted KV cell shape changes and the anteroposterior distribution of KV cilia. Similar defects were observed in Rock2b depleted embryos. Furthermore, inhibiting Myosin II at specific stages of KV development perturbed asymmetric flow and left-right asymmetry. These results indicate that regional cell shape changes control the development of anteroposterior asymmetry in KV, which is necessary to generate coordinated asymmetric fluid flow and left-right patterning of the embryo.
纤毛产生的流动在几个脊椎动物胚胎的“不对称器官”中对于建立左右身体轴至关重要。然而，关于运动纤毛如何产生协调的流动和不对称信号的细胞生物学还没有很好地定义。在斑马鱼的不对称器官——称为 Kupffer 泡（KV）中，纤毛细胞沿着前后轴不对称排列，使得更多的纤毛位于前区。我们之前证明了 Rho 激酶 2b（Rock2b）是 KV 中前后不对称和流动所必需的，但仍然不清楚在 KV 发育过程中纤毛细胞的分布如何变得不对称。在这里，我们确定了一个我们称之为“KV 重塑”的形态发生过程，该过程将 KV 结构中的初始对称性转化为前后不对称性。对 KV 细胞的实时成像显示了特定区域的细胞形状变化，这些变化介导了纤毛细胞紧密地聚集在前极。数学模型表明，前区和后区 KV 细胞中不同的界面张力参与了 KV 重塑。干扰非肌肉肌球蛋白 II（称为肌球蛋白 II）的活性，它调节细胞界面张力，并受 Rock 蛋白调节，会破坏 KV 细胞形状的变化和 KV 纤毛的前后分布。在 Rock2b 耗尽的胚胎中也观察到了类似的缺陷。此外，在 KV 发育的特定阶段抑制肌球蛋白 II 会干扰不对称流动和左右不对称。这些结果表明，区域细胞形状变化控制着 KV 前后不对称的发育，这对于产生协调的不对称流动和胚胎的左右模式至关重要。
