How to wrinkle a cell: Emerging mechanisms of microridge morphogenesis.

Microridges are laterally elongated actin-based protrusions arranged in striking maze-like patterns on the apical surfaces of mucosal epithelial cells. Recent studies have begun to reveal the molecular and mechanical factors that regulate microridge morphogenesis and allow them to adopt their unique properties. Microridges form from the coalescence of short actin-filled precursor protrusions called pegs. Microridge morphogenesis requires the establishment of apicobasal polarity, cortical myosin contraction, and Arp2/3 activity. Mature microridges contain branched actin networks, keratin filaments, and plakin cytolinkers that likely connect the two cytoskeletal elements. Once formed, microridges rearrange by fission and fusion to form increasingly regular patterns. Their highly organized arrangement provides an exciting system in which to study the interplay between molecular signaling and physical forces in the formation of subcellular patterns.