TY - JOUR T1 - Non-canonical apical constriction shapes emergent matrices in <em>C. elegans</em> JF - bioRxiv DO - 10.1101/189951 SP - 189951 AU - Sophie S. Katz AU - Alison R. Frand Y1 - 2018/01/01 UR - http://biorxiv.org/content/early/2018/01/01/189951.abstract N2 - We describe a morphogenetic mechanism that integrates apical constriction with remodeling apical extracellular matrices. Therein, a pulse of anisotropic constriction generates transient epithelial protrusions coupled to an interim apical matrix, which then patterns long durable ridges on C. elegans cuticles.ABSTRACT Specialized epithelia produce intricate apical matrices by poorly defined mechanisms. To address this question, we studied the role of apical constriction in patterning the acellular cuticle of C. elegans. Knocking-down epidermal actin, non-muscle myosin II or alpha-catenin led to the formation of mazes, rather than long ridges (alae) on the midline; yet, these same knockdowns did not appreciably affect the pattern of circumferential bands (annuli). Imaging epidermal F-actin and cell-cell junctions revealed that longitudinal apical-lateral and apical-medial AFBs, in addition to cortical meshwork, assemble when the fused seam narrows rapidly; and that discontinuous junctions appear as the seam gradually widens. Ultrastructural analyses showed three protrusions beneath an interim matrix at peak of constriction, then relax to form a pocket in which the final ECM is deposited. Knocking-down actin abrogated the lateral pattern of two interim matrix (sheath) components. However, the circumferential pattern of the sheath remained. This and other findings contradict the model the annuli are patterned by circumferential actin filament bundles (CFBs). Instead, CFBs may comprise a temporary musculoskeletal system assembled to withstand the molt. Finally, knocking-down specific components of the sheath resulted in cuticle mazes. We propose that dynamic interactions among cortical actin networks, cell-cell junctions and apical matrices together control pulsatile constriction and pre-pattern the alae. Cell-aECM interactions may likewise affect outcome of AC in higher metazoans. ER -