Odad1 is Required for Deployment of Axonemal Outer Arm Dyneins and Embryonic Left-Right Patterning

Motile cilia generate fluid flow required for development and tissue homeostasis. Defects in ciliary motility cause Primary Ciliary Dyskinesia (PCD), presenting with situs inversus, infertility, chronic respiratory disease, and hydrocephalus. Ciliary beating requires outer dynein arms (ODAs), anchored to microtubules by the ODA docking complex (ODA-DC). ODAD1 is an ODA-DC component and a known PCD protein. ODAD1 alleles are often associated with human laterality defects, however Odad1 has not been reported to localize to 9+0 axonemes. Here, we show that GFP-Odad1 localizes to nodal cilia (9+0) in the gastrocoel roof plate (GRP), the frog’s equivalent to the mammalian node where left-right asymmetry is first established. We found that Odad1 knockdown (KD) disrupts left-right patterning in Xenopus , with loss of pitx2 expression and abnormal gut looping reflecting defective 9+0 nodal cilia at the GRP. In 9+2 multiciliated cells (MCC) axonemes, Odad1 loss impaired deployment of ODA motors and ODA-DC subunits, disrupting ciliary motility. Two patient-derived truncating ODAD1 alleles were similarly unstable, failing to rescue ODA docking in MCCs or left-right patterning at the GRP. Together, these results show ODAD1 is required for ODA-DC assembly in both 9+0 and 9+2 cilia, linking its loss to ciliary motility and left-right patterning defects in ODAD1-associated ciliopathy.