Chiral Forces Organize Left-Right Patterning in C. elegans by Uncoupling Midline and Anteroposterior Axis

SummaryLeft-right (LR) patterning is an intriguing but poorly understood process of bilaterian embryogenesis. We report a mechanism for LR patterning in C. elegans in which the embryo uncouples its midline from the anteroposterior (AP) axis. Specifically, the eight-cell embryo establishes a midline that is tilted rightward from the AP axis and positions more cells on the left, allowing subsequent differential LR fate inductions. To establish the tilted midline, cells exhibit LR asymmetric protrusions and a handed collective movement. This process, termed chiral morphogenesis, involves differential regulation of cortical contractility between a pair of sister cells that are bilateral counterparts fate-wise and is activated by noncanonical Wnt signaling. Chiral morphogenesis is timed by the cytokinetic furrow of a neighbor of the sister pair, providing a developmental clock and an unexpected signaling interaction between the contractile ring and the adjacent cells.

Graphical AbstractFigure optionsDownload high-quality image (351 K)Download as PowerPoint slideHighlights
► Left-right patterning strategy involving uncoupling the midline and AP axis
► Midline tilting achieved through directed cell protrusion without fate change
► Noncanonical Wnt signaling activates cortical dynamics
► Signaling from the contractile ring to neighboring cells mediates timing