Fig. 2.

Rotations are characterized by strong homotypic cell-cell interactions. (A) Scheme of an inversion (top) and fitting a four-parameter logistic function to the empiric data of the absolute cumulative angles (bottom), revealing the three phases of the inversion process. Green dot represents the transition between Phases 1 and 2, and the blue dot between Phases 2 and 3. These transitions are called onset and termination, respectively. (B) Distance between sibling hair cells (HC) during the three phases. Sibling cells are closest during Phase 2. (C) Time-resolved cumulative angular change (top) for a representative cell pair from Time 0. The two dashed vertical lines mark the beginning and end of the rotation. A negative angle change indicates a clockwise direction of rotation. (D) Circularity of the same cell pair, which, taken as a unit, reaches maximal circularity during Phase 2. The onset and termination of inversion are marked by dashed vertical lines. (E) Length of the junction between hair cell pairs, which is highest during Phase 2. (F) Comparison of mean circularity for inverting and non-inverting cell pairs during the three phases. Phase 2 is characterized by a significantly higher circularity than Phase 1, and the circularity drops dramatically in Phase 3. The circularity for non-inverting pairs is comparable to the Phase 3 of inverting pairs. Trivially, for non-inverting cells there is a single phase. **P<0.01, Wilcoxon rank sum test. Box plots show median values (middle bars) and first (Q1) to third (Q3) interquartile ranges (boxes); upper whisker is either 1.5× the interquartile range or the maximum value (whichever is the smallest) and lower whisker is either 1.5× the interquartile range or the minimum value (whichever is the biggest). Each point represents the cells during a rotation.