Actin-based protrusions vary in morphology, stability, and arrangement on cell surfaces. Microridges are laterally-elongated protrusions arranged in maze-like patterns on mucosal epithelial cells that rearrange dynamically by fission and fusion. To characterize how microridges mature and investigate the mechanisms driving fission and fusion, we imaged microridges in the maturing skin of zebrafish larvae. After their initial development, microridges continued to lengthen and microridge alignment became increasingly well ordered. Imaging F-actin and Non-Muscle Myosin II (NMII) revealed that microridge fission and fusion were associated with local NMII activity in the apical cortex. Inhibiting NMII blocked rearrangements, reduced microridge density, and altered microridge spacing. High-resolution imaging revealed that individual cortical NMII minifilaments are tethered to protrusions, often connecting adjacent microridges. NMII minifilaments connecting the ends of microridges fused them together, whereas minifilaments oriented perpendicular to microridges severed them or pulled them closer together. Our findings demonstrate that as cells mature, microridges continue to remodel and form an increasingly orderly arrangement through a process orchestrated by cortical NMII contraction.

中文翻译：

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皮质肌球蛋白微丝编排上皮细胞表面微脊突起的排列

基于肌动蛋白的突起在细胞表面的形态，稳定性和排列方面有所不同。微脊是粘膜上皮细胞上呈迷宫状排列的横向延伸的突起，通过裂变和融合而动态重排。为了表征微脊如何成熟并研究引起裂变和融合的机制，我们对斑马鱼幼虫成熟皮肤中的微脊进行了成像。在其最初的发展之后，微脊继续延长，微脊的排列变得越来越有序。对F-肌动蛋白和非肌肉肌球蛋白II（NMII）进行成像显示，微脊裂和融合与顶皮层中的局部NMII活性有关。抑制NMII可阻止重排，降低微脊密度并改变微脊间距。高分辨率成像显示，单个皮质NMII细丝束缚于突起，通常连接相邻的微脊。连接微脊末端的NMII细丝将它们融合在一起，而垂直于微脊取向的细丝将它们切断或拉近。我们的研究结果表明，随着细胞的成熟，微脊通过皮质NMII收缩精心策划的过程继续重塑并形成越来越有序的排列。