Hydin (red) is found on the central pair apparatus of flagella.

Hydin is hiding no longer. On page 473, Lechtreck and Witman locate this protein to the buried central pair (CP) of flagellar microtubules. The paralysis of cilia lacking hydin might be a basis for hydrocephalus-inducing brain fluid accumulation.

Flagella contain lots of hydin, but no one had yet localized the protein in any system. Lechtreck and Witman have now spotted the protein on the CP of flagellar microtubules in Chlamydomonas.

This alga's two flagella execute a sort of breaststroke that provides motility. The downward stroke that moves the cell forward requires active dynein on one side of the outer ring of microtubule doublets. But to return the arms to their starting position, dynein on the opposite side must be activated.

This dynein switch appears to be defective in algae lacking hydin, whose...

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