How Does Cilium Length Affect Beating?

Abstract

The effects of cilium length on the dynamics of cilia motion were investigated by high-speed video microscopy of uniciliated mutants of the swimming alga, Chlamydomonas reinhardtii. Cells with short cilia were obtained by deciliating cells via pH shock and allowing cilia to reassemble for limited times. The frequency of cilia beating was estimated from the motion of the cell body and of the cilium. Key features of the ciliary waveform were quantified from polynomial curves fitted to the cilium in each image frame. Most notably, periodic beating did not emerge until the cilium reached a critical length between 2 and 4 mm. Surprisingly, in cells that exhibited periodic beating, the frequency of beating was similar for all lengths with only a slight decrease in frequency as length increased from 4 mm to the normal length of 10-12 mm. The waveform average curvature (rad/mm) was also conserved as the cilium grew. The mechanical metrics of ciliary propulsion (force, torque, and power) all increased in proportion to length. The mechanical efficiency of beating appeared to be maximal at the normal wild-type length of 10-12 mm. These quantitative features of ciliary behavior illuminate the biophysics of cilia motion and, in future studies, may help distinguish competing hypotheses of the underlying mechanism of oscillation.

Mutation of CFAP57, a protein required for the asymmetric targeting of a subset of inner dynein arms in Chlamydomonas, causes primary ciliary dyskinesia

“…To characterize the waveform of mutants, both the fap57-050 and fap57-706 mutants were crossed with the uniciliate mutant uni1-2 [70]. Fifty movies of fap57-050; uni1 and 51 movies of fap57-706; uni1 were compared to 153 movies of uni1-2 (the wild-type group was previously described by Bottier et al [71]) ( Fig 5A, S6 Fig). Body motion analysis shows that both mutants have a significantly slower body rotation rate compared to wild-type cells (Fig 5C), which agrees with the reduced velocity.…”

“…The single mutant uni1 is considered the wild-type reference as previously published [70]. Videos were analyzed using a custom-made program written in Matlab R2016a (The Mathworks, Natick, MA, USA) previously published [71]. From each video, a sequence of 200 consecutive frames was stored in a 3D matrix of pixel intensity values.…”

Mutation ofCFAP57causes primary ciliary dyskinesia by disrupting the asymmetric targeting of a subset of ciliary inner dynein arms

“…To characterize the waveform of mutants, both the fap57-050 and fap57-706 mutants were crossed with the uniciliate mutant uni1-2 (3). Fifty movies of fap57-050; uni1 and 51 movies of fap57-706; uni1 were compared to 153 movies of uni1-2 (wild-type samples previously described by Bottier et al (44) (Fig. 5a).…”

“…The single mutant uni1 is considered the wild-type reference as previously published (43). Videos were analyzed using a custom-made program written in Matlab R2016a (The Mathworks, Natick, MA, USA) previously published (44). From each video, a sequence of 200 consecutive frames was stored in a 3D matrix of pixel intensity values.…”

“…Components of the forces exerted by cilia on the fluid are directly calculated from the Cartesian coordinates using parameters previously reported (44).…”