RGS22 is a metazoa-specific radial spoke component required for coordinated ciliary beating.

In metazoan epithelia, arrays of motile cilia beat in a tissue-wide coordinated manner to drive unidirectional fluid flow. Whether radial spokes (RSs), which mediate mechano-signal transduction between the central pair and axonemal dynein arms, acquire metazoa-specific subunit(s) in evolution to facilitate this function remains poorly known. Here we report that Gα-GTPase activating protein family member RGS22 is a metazoa-specific component of RS1/2 complexes. Mouse Rgs22-deficient motile cilia exhibit ultrastructural defects, including deformation of the RS1 and disorganization of outer dynein arms. These abnormalities correlate with impaired planar polarity, manifested as unsynchronized ciliary beating and disrupted rotational polarity of basal bodies across the ependyma. The motility deficits further lead to progressive ciliary loss and shortening, resulting in postnatal hydrocephalus. Together, our data identify RGS22 an animal-lineage RS1/2 component required for normal RS architecture and associated with tissue-level ciliary motility and coordination phenotypes.