A one-dimensional model of PCP signaling: Polarized cell behavior in the notochord of the ascidian Ciona

• The Ciona notochord presents a unique single-file geometry for PCP studies.
• Notochord cells display an anterior/posterior polarity.
• PCP signaling coordinates polarity in a posterior to anterior direction.
• PCP signaling acts only between neighboring cells.
• cell ablation studies show dynamic regulation of cell polarity.

Despite its importance in development and physiology the planar cell polarity (PCP) pathway remains one of the most enigmatic signaling mechanisms. The notochord of the ascidian Ciona provides a unique model for investigating the PCP pathway. Interestingly, the no