Abstract
Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by airway disease, infertility, and laterality defects, often caused by dual loss of the inner dynein arms (IDAs) and outer dynein arms (ODAs), which power cilia and flagella beating. Using whole-exome and candidate-gene Sanger resequencing in PCD-affected families afflicted with combined IDA and ODA defects, we found that 6/38 (16%) carried biallelic mutations in the conserved zinc-finger gene BLU (ZMYND10). ZMYND10 mutations conferred dynein-arm loss seen at the ultrastructural and immunofluorescence level and complete cilia immotility, except in hypomorphic p.Val16Gly (c.47T>G) homozygote individuals, whose cilia retained a stiff and slowed beat. In mice, Zmynd10 mRNA is restricted to regions containing motile cilia. In a Drosophila model of PCD, Zmynd10 is exclusively expressed in cells with motile cilia: chordotonal sensory neurons and sperm. In these cells, P-element-mediated gene silencing caused IDA and ODA defects, proprioception deficits, and sterility due to immotile sperm. Drosophila Zmynd10 with an equivalent c.47T>G (p.Val16Gly) missense change rescued mutant male sterility less than the wild-type did. Tagged Drosophila ZMYND10 is localized primarily to the cytoplasm, and human ZMYND10 interacts with LRRC6, another cytoplasmically localized protein altered in PCD. Using a fly model of PCD, we conclude that ZMYND10 is a cytoplasmic protein required for IDA and ODA assembly and that its variants cause ciliary dysmotility and PCD with laterality defects.
Highlights
Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by airway disease, infertility, and laterality defects, often caused by dual loss of the inner dynein arms (IDAs) and outer dynein arms (ODAs), which power cilia and flagella beating
Structures attached along the axoneme govern ciliary beating via a highly regulated and synchronous sliding between microtubules and regulate dynein activity
A distinct set of six proteins altered in PCD are either solely localized to the cytoplasm or found in both the cytoplasm and the axoneme: DNAAF1 (LRRC50), DNAAF2 (KTU), DNAAF3, CCDC103, HEATR2, and LRRC6.24–30 These are most likely involved in the cytoplasmic preassembly of dynein-arm complexes prior to their movement into the axoneme and/or in axonemal transport and attachment processes for the dynein-arm complexes
Summary
Primary ciliary dyskinesia (PCD) is a ciliopathy characterized by airway disease, infertility, and laterality defects, often caused by dual loss of the inner dynein arms (IDAs) and outer dynein arms (ODAs), which power cilia and flagella beating. ZMYND10 is present in the Cildb ciliome database.[37] It was reported to have a likely role in ciliary motility because its expression is 14-fold higher in ciliated primary human airway epithelial cells upon stimulation of ciliogenesis by transfer to air-liquid interface culture[38] and from expression profiling of bronchial biopsies from PCD cases.[39] The exome-sequencing coverage in the three affected individuals is detailed, available online, and their variant calling and filtering are summarized in Tables S2 and S3.
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