Abstract
Microvilli are actin bundle-supported membrane protrusions essential for absorption, secretion, and sensation. Microvilli defects cause gastrointestinal disorders; however, mechanisms controlling microvilli formation and organization remain unresolved. Here, we study microvilli by vitrifying the C. elegans larvae with high-pressure freezing, thinning them by cryo-focused ion beam milling, cryo-electron tomography, and sub-tomogram averaging. We uncover that hundreds of previously unrecognized stick-like structures, which we refer to as nanosticks, decorate the lateral surface of microvilli. Nanosticks are 37.5-nm long and 4.5-nm wide, and their formation requires the protocadherin family protein CDH-8. Loss of nanosticks slows down animal growth and increases the number of Y-shaped microvilli, the putative intermediate structures, when a microvillus splits from its tip and separates into two. We suggest that an existing microvillus may divide to form two nascent microvilli with uniformity and that nanosticks may space microvilli.
Published Version
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