Tubulin glycylation controls sperm motility.

(A) Microtubules in sperm flagella are rich in tubulin posttranslational modifications. Mice deficient for the glycylating enzymes TTLL3 and TTLL8 lack glycylation. (B) Mammalian sperm swim in linear paths. In the absence of glycylation, abnormal, mostly circular swimming patterns are observed, which impede progressive swimming. (C) Absence of glycylation leads to perturbed distribution of axonemal dynein conformations in Ttll3 ^−/− Ttll8 ^−/− flagella, which impedes normal flagellar beating.