DAW1 (dynein assembly factor with WD repeats 1) is a conserved protein required for axonemal dynein arm assembly and ciliary motility during embryonic development 1. As a homolog of Chlamydomonas ODA16, DAW1 facilitates the import and assembly of dynein complexes into axonemal microtubules, promoting robust cilia motility onset 2. DAW1 functions across diverse ciliated tissues, including Kupffer's vesicle, epidermis, and protonephridia, where it maintains ciliary function rather than cilia biogenesis per se 3. In development, DAW1 is specifically expressed in motile ciliated cells of the embryonic node and is critical for left-right axis patterning 1. Biallelic DAW1 variants cause motile ciliopathy characterized by laterality defects, congenital heart disease, and variable respiratory symptoms 1. Loss-of-function variants impair distal outer dynein arm assembly, reducing cilia-induced fluid flow 1. Notably, tissue-specific effects occur with certain missense variants: some alleles fully rescue mucociliary clearance but fail to restore left-right patterning 4. This demonstrates context-dependent hypomorphic function. DAW1 mutations typically do not cause classical primary ciliary dyskinesia despite respiratory involvement, distinguishing motile ciliopathy from primary ciliary dyskinesia, a distinction explaining why approximately 30% of ciliary dyskinesia patients lack traditional PCD diagnoses 1.