Microvilli are actin bundle supported surface protrusions that play essential roles in diverse epithelial cell functions. To develop our understanding of microvilli biogenesis, we used live imaging to directly visualize protrusion growth at early stages of epithelial differentiation. Time-lapse data revealed that an 'initiation complex' enriched in EPS8 and IRTKS appears at future sites of microvillus growth minutes before core actin bundle assembly. Elongation of a new core bundle occurs in parallel with the arrival of EZRIN and plasma membrane encapsulation. In addition to de novo growth, we also observed that new microvilli emerge from pre-existing protrusions. Additionally, we found that new microvilli can also collapse, characterized first by loss of membrane wrapping and Ezrin enrichment, followed by a sharp decrease in distal tip EPS8 and IRTKS. These studies are the first to offer a temporally resolved microvillus growth mechanism and highlight critical factors that drive this process.

中文翻译：

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直接可视化上皮微绒毛的生物发生

微绒毛是肌动蛋白束支持的表面突起，在各种上皮细胞功能中起重要作用。为了增进对微绒毛生物发生的理解，我们使用实时成像直接观察了上皮分化早期的突起生长。延时数据显示，在核心肌动蛋白束组装之前的几分钟内，在微绒毛生长的未来站点出现了富含EPS8和IRTKS的“起始复合物”。新核心束的延伸与EZRIN的到来和质膜包封同时发生。除从头生长外，我们还观察到新的微绒毛从先前存在的突起中出现。此外，我们发现新的微绒毛也可能塌陷，其特征首先是膜包裹物丢失和Ezrin浓缩，随后远端末梢EPS8和IRTKS急剧下降。这些研究是第一个提供暂时解决的微绒毛生长机制并突出显示驱动该过程的关键因素的研究。