Babcock Donner F, Wandernoth Petra M, Wennemuth Gunther
Department of Physiology and Biophysics, University of Washington, Seattle, WA, 98195-7290, USA.
Institute for Anatomy, University Hospital, Duisburg-Essen University, Essen, 45141, Germany.
BMC Biol. 2014 Aug 16;12:67. doi: 10.1186/s12915-014-0067-3.
Frequency and asymmetry of the flagellar waveform of sperm are controlled by cAMP-mediated and Ca(2+)-dependent signaling pathways, but additional mechanisms modulate sperm swimming behavior. Here, high-speed imaging of free-swimming mouse sperm simultaneously reports flagellar waveform, orientation of sperm head, and swimming paths.
We found many sperm roll (rotate around their long axis) at intervals closely tied to flagellar beat frequency, allowing an asymmetrical flagellar beat to form linear averaged swimming trajectories. For non-rolling sperm, flagellar waveform asymmetry dictated circular path trajectories. Sparse rolling produced abrupt changes in swimming trajectories that occurred spontaneously, unaffected by blockade or engagement of cAMP- or Ca(2+)-mediated flagellar responses. Still other sperm loosely attached (tethered) to surfaces or other cells. Sperm tethered to each other in duos or trios could have narrowed swimming paths, allowing enhanced progression.
We propose that transient episodes of rolling and reversible attachments are organizing principles that determine diverse swimming behaviors, which may have roles in selection of the fertilizing sperm.
精子鞭毛波形的频率和不对称性由环磷酸腺苷（cAMP）介导的信号通路和钙离子（Ca²⁺）依赖的信号通路控制，但还有其他机制调节精子的游动行为。在此，对自由游动的小鼠精子进行高速成像，可同时记录鞭毛波形、精子头部的方向和游动路径。
我们发现许多精子会以与鞭毛搏动频率紧密相关的间隔进行翻滚（绕其长轴旋转），使不对称的鞭毛搏动形成线性平均游动轨迹。对于不翻滚的精子，鞭毛波形的不对称性决定了圆形路径轨迹。稀疏的翻滚会使游动轨迹发生自发的突然变化，不受cAMP或Ca²⁺介导的鞭毛反应的阻断或参与的影响。还有其他精子会松散地附着（拴系）在表面或其他细胞上。成对或成三联体相互拴系的精子可能会使游动路径变窄，从而提高前进速度。
我们提出，翻滚和可逆附着的短暂事件是决定多种游动行为的组织原则，这些行为可能在受精精子的选择中发挥作用。
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