The Joubert syndrome protein CSPP1 is a conserved regulator of vertebrate multiciliogenesis and motile cilia function

Cilia are conserved microtubule-based organelles required for signaling and fluid transport, and their dysfunction causes ciliopathies. Clinical overlap between sensory and motile ciliopathies suggests that primary and motile ciliogenesis depend on shared regulatory modules. Here, we identify Centrosome and Spindle Pole-associated Protein 1 (CSPP1), a microtubule-associated protein mutated in the neurodevelopmental ciliopathy Joubert syndrome, as a conserved regulator of vertebrate multiciliogenesis. Using mouse tracheal epithelial cultures and Xenopus embryonic epidermis, we show that CSPP1 localizes to fibrous granules and deuterosomes during centriole amplification, and to basal bodies and ciliary axonemes in differentiated multiciliated cells. Loss of CSPP1 impairs centriole amplification, basal body apical migration, spacing, and rotational polarity, and is accompanied by disorganization of the apical microtubule network. CSPP1 depletion also disrupts axoneme assembly, resulting in fewer and shorter cilia with ultrastructural defects, reduced ciliary beating, and impaired cilia driven fluid flow in vivo. Together, our findings identify CSPP1 as a conserved regulator of multiciliogenesis and motile cilia function and establish a basis for future work on how shared cytoskeletal pathways may underlie overlapping features of sensory and motile ciliopathies.