Cilium-specific protein required for cilia structures. Axonemal dynein-associated protein that participates in a structural link between inner and outer row dyneins. Interacts with both outer row and I1 inner row dyneins. Absence of outer row dynein and a reduced flagellar beat. Axonemal outer row dynein assembly is prevented by blocking association of heavy chains and intermediate chains in the cytoplasm. Belongs to the DNAAF1 family.