Dynamic microvilli sculpt bristles at nanometric scale

Area of Science:

• Cell biology
• Biomaterials science
• Developmental biology

Background:

• Organismal shape generation occurs across diverse size scales.
• Principles of micrometric and submicrometric structure formation are poorly understood.
• Polychaete annelid chaetoblasts produce stereotypic chitinous bristles.

Purpose of the Study:

• Investigate the cellular mechanisms of micro- to submicrometric biomaterial sculpting.
• Elucidate the role of chaetoblasts and their surface structures in bristle formation.
• Determine the molecular basis for chitinous bristle geometry.

Main Methods:

• Serial block-face electron microscopy for bristle reconstruction.
• Pharmacological manipulation of actin dynamics.
• Analysis of chitin-producing enzyme expression in chaetoblasts.

Main Results:

• Bristle formation necessitates a specific chitin-producing enzyme expressed in chaetoblasts.
• Chaetoblasts display dynamic actin-rich microvilli on their cell surfaces.
• Microvilli exhibit an extension-disassembly cycle for chitin deposition, mimicking 3D printing.
• Interference with actin dynamics disrupts chitinous tooth formation.

Conclusions:

• Chaetoblasts are central to both material composition and shape determination of bristles.
• Cellular microvilli are key effectors in the micro- to submicrometric sculpting of biomaterials.
• The study reveals a novel mechanism for biomineralization and morphogenesis at the microscale.