Cilia-independent requirements for Ccdc103 promoting proliferation and migration of myeloid cells

The pathology of primary ciliary dyskinesia (PCD) is predominantly attributed to impairment of motile cilia. However, PCD patients also have perplexing functional defects in myeloid cells, which lack motile cilia. Here, we show Coiled-coiled domain containing protein 103 (CCDC103), mutations in which underlie PCD, is required for the proliferation and directed migration of myeloid cells. CCDC103 co-localizes with cytoplasmic microtubules in human myeloid cells. Zebrafish ccdc103 / schmalhans ( smh ) mutants have reduced macrophage and neutrophil proliferation, rounded cell morphology, and an inability to migrate efficiently to the site of sterile wounds. Furthermore, we demonstrate that direct interactions between CCDC103 and Sperm associated antigen 6 (SPAG6), which also promotes microtubule stability, are abrogated by CCDC103 mutations from PCD patients, and that spag6 zebrafish mutants recapitulate the myeloid defects of smh mutants. In summary, we have illuminated a mechanism, independent of motile cilia, to explain functional defects in myeloid cells from PCD patients. Summary Statement We show Ccdc103 regulates myeloid migration and proliferation independent of cilia in zebrafish and that mutations in CCDC103 that cause primary ciliary dyskinesia abrogate interactions with the microtubule-stabilizing protein SPAG6.