Hydrocephalus is one of the most prevalent form of developmental central nervous system (CNS) malformations. Cerebrospinal fluid (CSF) flow depends on both heartbeat and body movement. Furthermore, it has been shown that CSF flow within and across brain ventricles depends on cilia motility of the ependymal cells lining the brain ventricles, which play a crucial role to maintain patency of the narrow sites of CSF passage during brain formation in mice. Using whole-exome and whole-genome sequencing, we identified an autosomal-dominant cause of a distinct motile ciliopathy related to defective ciliogenesis of the ependymal cilia in six individuals. Heterozygous de novo mutations in FOXJ1, which encodes a well-known member of the forkhead transcription factors important for ciliogenesis of motile cilia, cause a motile ciliopathy that is characterized by hydrocephalus internus, chronic destructive airway disease, and randomization of left/right body asymmetry. Mutant respiratory epithelial cells are unable to generate a fluid flow and exhibit a reduced number of cilia per cell, as documented by high-speed video microscopy (HVMA), transmission electron microscopy (TEM), and immunofluorescence analysis (IF). TEM and IF demonstrate mislocalized basal bodies. In line with this finding, the focal adhesion protein PTK2 displays aberrant localization in the cytoplasm of the mutant respiratory epithelial cells.

Dysfunction of motile monocilia, altering the leftward flow at the embryonic node essential for determination of left-right body asymmetry, is a major cause of laterality defects. Laterality defects are also often associated with reduced mucociliary clearance caused by defective multiple motile cilia of the airway and are responsible for destructive airway disease. Outer dynein arms (ODAs) are essential for ciliary beat generation, and human respiratory cilia contain different ODA heavy chains (HCs): the panaxonemally distributed γ-HC DNAH5, proximally located β-HC DNAH11 (defining ODA type 1), and the distally localized β-HC DNAH9 (defining ODA type 2). Here we report loss-of-function mutations in DNAH9 in five independent families causing situs abnormalities associated with subtle respiratory ciliary dysfunction. Consistent with the observed subtle respiratory phenotype, high-speed video microscopy demonstrates distally impaired ciliary bending in DNAH9 mutant respiratory cilia. DNAH9 -deficient cilia also lack other ODA components such as DNAH5, DNAI1, and DNAI2 from the distal axonemal compartment, demonstrating an essential role of DNAH9 for distal axonemal assembly of ODAs type 2. Yeast two-hybrid and co-immunoprecipitation analyses indicate interaction of DNAH9 with the ODA components DNAH5 and DNAI2 as well as the ODA-docking complex component CCDC114. We further show that during ciliogenesis of respiratory cilia, first proximally located DNAH11 and then distally located DNAH9 is assembled in the axoneme. We propose that the β-HC paralogs DNAH9 and DNAH11 achieved specific functional roles for the distinct axonemal compartments during evolution with human DNAH9 function matching that of ancient β-HCs such as that of the unicellular Chlamydomonas reinhardtii .

Primary ciliary dyskinesia (PCD) is characterized by chronic airway disease, male infertility, and randomization of the left/right body axis as a result of defects of motile cilia and sperm flagella. We identified loss-of-function mutations in the open-reading frame C11orf70 in PCD individuals from five distinct families. Transmission electron microscopy analyses and high-resolution immunofluorescence microscopy demonstrate that loss-of-function mutations in C11orf70 cause immotility of respiratory cilia and sperm flagella, respectively, as a result of the loss of axonemal outer (ODAs) and inner dynein arms (IDAs), indicating that C11orf70 is involved in cytoplasmic assembly of dynein arms. Expression analyses of C11orf70 showed that C11orf70 is expressed in ciliated respiratory cells and that the expression of C11orf70 is upregulated during ciliogenesis, similar to other previously described cytoplasmic dynein-arm assembly factors. Furthermore, C11orf70 shows an interaction with cytoplasmic ODA/IDA assembly factor DNAAF2, supporting our hypothesis that C11orf70 is a preassembly factor involved in the pathogenesis of PCD. The identification of additional genetic defects that cause PCD and male infertility is of great importance for the clinic as well as for genetic counselling.

Primary ciliary dyskinesia (PCD) is characterized by chronic airway disease, male infertility and randomization of the left/right body axis caused by defects of motile cilia and sperm flagella. We identified loss-of-function mutations in the open reading frame C11ORF70 in PCD individuals from five distinct families. Transmission electron microscopy analyses and high resolution immunofluorescence microscopy demonstrate that loss-of-function mutations in C11ORF70 cause immotility of respiratory cilia and sperm flagella, respectively, due to loss of axonemal outer (ODAs) and inner dynein arms (IDAs), indicating that C11ORF70 is involved in cytoplasmic assembly of dynein arms. Expression analyses of C11ORF70 showed that C11ORF70 is expressed in ciliated respiratory cells and that the expression of C11ORF70 is upregulated during ciliogenesis, similar to other previously described cytoplasmic dynein arm assembly factors. Furthermore, C11ORF70 shows an interaction with cytoplasmic ODA/IDA assembly factor DNAAF2, supporting our hypothesis that C11ORF70 is a novel preassembly factor involved in the pathogenesis of PCD. The identification of a novel genetic defect that causes PCD and male infertility is of great clinical importance as well as for genetic counselling.

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