Mechanical Strain Determines Cilia Length, Motility, and Planar Position in the Left-Right Organizer

Highlights

• Different ciliated cells in the left-right organizer (LRO) produce and sense fluid flow

• Mechanical strain in the Xenopus LRO specifies flow producing ciliated cells

• Mechanical strain also specifies a global planar axis required for leftward flow

• Strain is a developmental cue linking cilia planar positioning and motile differentiation

Summary

The Xenopus left-right organizer (LRO) breaks symmetry along the left-right axis of the early embryo by producing and sensing directed ciliary flow as a patterning cue. To carry out this process, the LRO contains different ciliated cell types that vary in cilia length, whether they are motile or sensory, and how they position their cilia along the anterior-posterior (A-P) planar axis. Here, we show that these different cilia features are specified in the prospective LRO during gastrulation, based on anisotropic mechanical strain that is oriented along the A-P axis, and graded in levels along the medial-lateral axis. Strain instructs ciliated cell differentiation by acting on a mesodermal prepattern present at blastula stages, involving foxj1. We propose that differential strain is a graded, developmental cue, linking the establishment of an A-P planar axis to cilia length, motility, and planar location during formation of the Xenopus LRO.