DNAI 2 mutations can cause primary ciliary dyskinesia with outer dynein arm defects

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder characterized by recurrent infections of the airways and randomization of left/right body asymmetry. The phenotype results from dysfunction of motile cilia of the respiratory epithelium and the embryonic node. Dysmotile sperm tails often cause infertility in male PCD patients. Underlying ultrastructural defects frequently involve outer dynein arms (ODA), which are responsible for generation of cilia movement. We recently showed that recessive mutations of DNAH5 encoding a heavy dynein chain are frequently found in PCD with ODA defects. Genes (DNAI1, TXNDC3, DNAH11) encoding for other ODA components can also account for PCD. Here, we analyzed the protein expression of the ODA intermediate chain DNAI2 and found sub-localization throughout respiratory cilia and sperm tails. Mutational screening of 105 PCD families revealed in one affected a homozygous mutation within the facultative splice acceptor site of exon 4. RNA studies confirmed absence of exon 4 in all transcripts predicting a premature stop codon. Consistently mutant respiratory cells lacked DNAI2 expression and exhibited ODA defects by electron microscopy. High-resolution immunofluorescence imaging demonstrated mis-localization of DNAH5 indicating that DNAI2 is essential for assembly of these ODA components. In addition we report homozygous loss-of-function DNAI2 mutations located within the obligatory splice donor site of exon 11 in four affected individuals with ODA defects originating from a consanguineous PCD family that showed significant linkage to the DNAI2 locus in a total genome scan. In summary, we provide the first evidence that DNAI2 can account for PCD with ODA defects.