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. 2020 Oct 30;8:597446. doi: 10.3389/fcell.2020.597446

FIGURE 1.

FIGURE 1

Polarity at different notochord development stages in Ciona. (A) Notochord cells form a mediolateral (ML) polarity to drive the migration to the midline during convergence and extension. The notochord elongates parallel to the anterior-posterior (AP) axis regulated by embryonic AP polarity signaling. The key PCP component protein Prickle is located at the notochord cell–cell contact domain. (B) Notochord cells form a dorsal-ventral (DV) polarity to abend tissue toward the ventral side. (C) After cell intercalation, the PCP direction changes from ML to 1D AP axis. The Prickle relocates at the anterior edge of each notochord cell. (D) Apical-basal (AB) polarity is built to induces extracellular lumen formation. Two apical domains appear in one notochord cell. (E) Notochord cells migrate bidirectionally to induce the lumen connection. Adjacent notochord cells flatten opposite to each other along the notochord sheath.