Loss-of-function variants in ODAD1 disrupt ODA docking and induce actin cytoskeletal remodeling in primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder characterized by defective mucociliary clearance due to impaired motile cilia function. Outer dynein arm docking complex subunit 1 (ODAD1) encodes a structural component of the outer dynein arm docking complex (ODA-DC), which is crucial for effective ciliary beating. However, the full spectrum of ODAD1-associated pathogenesis remains incompletely defined. Here, we identified one novel homozygous loss-of-function ODAD1 variant, c.705_706insGCAG, and a recurrent homozygous splicing variant, c.-41-2A > C, in seven unrelated patients. These patients exhibited hallmark PCD symptoms with reduced nasal nitric oxide levels and situs inversus. Patient-derived nasal epithelial cells and air‒liquid interface (ALI) cultures exhibited a markedly reduced ciliary beating frequency and severe motility defects. Transmission electron microscopy and cryo-electron microscopy showed a complete loss of outer dynein arms and docking complexes, with variant-specific ultrastructural abnormalities. Unexpectedly, ODAD1 deficiency also led to reduced multiciliated cells (MCCs) abundance, misoriented basal bodies, and impaired multiciliogenesis. Proteomic profiling and immunostaining revealed prominent actin cytoskeletal remodeling, including aberrant F-actin bundling throughout the epithelial layers. Pharmacological inhibition of actin polymerization using cytochalasin B partially rescued the abundance of MCCs and multiciliogenesis, indicating that actin dysregulation is a modifiable consequence of ODAD1 loss. Finally, lentiviral re-expression of wild-type ODAD1 in patient-derived organoids restored ODA assembly and rescued coordinated ciliary beating, confirming the pathogenicity of the identified variants. Our data reveal a dual role for ODAD1 in regulating both axonemal structure and epithelial cytoskeletal integrity and identify actin dysregulation as a previously unrecognized, targetable pathological mechanism of ODAD1-associated PCD.