Fig. 1.

Flow stiffens and rotates primary cilia. (A) Representative profiles of a cilium through two bouts of 2-min flow. For each bout of flow, the cilium is graphed at rest (solid line), at 30 s of flow (dashed line), and 2 min of flow (dotted line). The first 2-min flow is in black while the second 2-min flow is in red. The inset is of a representative fluorescence micrograph from which cilium position is determined. The x-axis is positioned at the junction of the cilium and the cell and the protrusion angle measures the orientation of the cilium with respect to the cell. Scale bar: 2.5 µm. (B) Cilia were exposed to 2-min (black) or 10-min (blue) bouts of flow separated by 2 min of rest. The bending stiffness of the cilium shaft was measured and normalized to the first measurement at 30 s. *P<0.05, n=6 per group. Stiffness increased with exposure to flow, but the increase is independent of duration of flow exposure. (C) Similarly, torsional stiffness anchoring the cilium increased after each rest period independently of flow exposure. (D) Plastic deformation of the cilium was observed in the protrusion angle, the angle between the cilium and the cell membrane. The resting position of the cilium changes with exposure to flow, decreasing the protrusion angle. *P<0.05 from initial resting position of cilium, n=6 per group. Data presented as mean±s.e.m.