Actin Dynamics Drive Microvillar Motility and Clustering during Brush Border Assembly

Area of Science:

• Cell Biology
• Epithelial Biology
• Cytoskeleton Dynamics

Background:

• Transporting epithelial cells possess microvilli, forming a brush border to increase surface area and functional capacity.
• Brush border formation involves apical remodeling, but the underlying mechanisms driving early organization are not fully understood.

Purpose of the Study:

• To investigate the dynamics of microvilli during early brush border formation.
• To identify the molecular mechanisms driving microvillar movement and its role in apical remodeling.

Main Methods:

• Live cell imaging to visualize microvillar behavior in real-time.
• Perturbation experiments using inhibitors and photokinetic analysis to probe motility drivers.
• Localization studies of actin regulatory factors (IRTKS, EPS8) at microvilli.

Main Results:

• Individual microvilli exhibit persistent active motility, moving at approximately 0.2 μm/min.
• Microvillar motility is driven by actin assembly at the barbed ends of core bundles, coupled with actin treadmilling.
• Actin regulatory factors IRTKS and EPS8 are key controllers of microvillar movement kinetics.
• Microvillar motility facilitates collisions, leading to clustering and the formation of organized higher-order arrays.

Conclusions:

• Microvillar motility is a novel, active process contributing significantly to brush border development.
• This motility is a fundamental driving force for apical surface remodeling and maturation in differentiating epithelial cells.
• Understanding microvillar dynamics provides new insights into epithelial cell structure and function.