REPORT Mutations in C11orf70 Cause Primary Ciliary Dyskinesia with Randomization of Left/Right Body Asymmetry Due to Defects of Outer and Inner Dynein Arms Inga M. Ho ¨ben, 1 Rim Hjeij, 1 Heike Olbrich, 1 Gerard W. Dougherty, 1 Tabea No ¨the-Menchen, 1 Isabella Aprea, 1 Diana Frank, 1 Petra Pennekamp, 1 Bernd Dworniczak, 1 Julia Wallmeier, 1 Johanna Raidt, 1 Kim G. Nielsen, 2 Maria C. Philipsen, 2 Francesca Santamaria, 3 Laura Venditto, 3 Israel Amirav, 4 Huda Mussaffi, 5,6 Freerk Prenzel, 7 Kaman Wu, 8 Zeineb Bakey, 8 Miriam Schmidts, 8,9 Niki T. Loges, 1,10 and Heymut Omran 1,10, * 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 micro- scopy 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. Further- more, 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. Cilia are hair-like organelles extending from nearly all types of polarized cells. Motile cilia in distinct cell types in the human body perform essential biological functions such as generation of fluid flow and mucociliary clearance of the airways. 1 The basic structure of motile cilia consists of a ring of nine peripheral microtubule doublets, which surround one central pair (9 þ 2 structure). The peripheral ring is connected to the central pair (CP) through radial spokes (RSs) and the nexin-dynein regulatory complex (N-DRC). The CP, the N-DRC, and the inner dynein arms (IDAs) are responsible for modulation and regulation of the ciliary beating 2,3 whereas the outer dynein arms (ODAs) are responsible for the beat generation. ODAs and IDAs are large multimeric protein complexes that are pre-assembled in the cytoplasm before transport to the ax- onemes. 4 There are at least two types of ODAs in humans: type 1, containing the axonemal dynein heavy chains (HCs) DNAH5 and DNAH11, located proximally, and type 2, containing the dynein HCs DNAH5 and DNAH9, located distally in the ciliary axonemes. 5,6 In Chlamydomo- nas reinhardtii, there are seven distinct IDA complexes, one double-headed and six single-headed. 7 The IDA I1 com- plex contains two HCs (a- and b-HC) and the intermedi- ate-chain light-chain complex (ICLC). 8 The six single- headed complexes can be divided into two groups on the basis of their association with specific light chains: the three IDA complexes of group I2 contain each one HC that associates with the dynein light chain p28. 7 The IDA complexes of group I3 also each contain one HC, which associates with centrin. 7 The identification of proteins responsible for the correct assembly and composition of these protein complexes is critical to understanding the disease mechanisms of motile-cilia-related disorders such as primary ciliary dyskinesia (PCD). Primary ciliary dykinesia (PCD) (MIM: 244400) is a rare genetic disorder caused by immotile or dyskinetic cilia and has a prevalence in the range of 1:4.000 to 1:20.000. 9 Ciliary dysfunction in upper and lower airways leads to defective mucociliary clearance of the airways and subse- quently to recurrent airway inflammation, bronchiectasis (Figure 1), and progressive lung failure. Dysfunction of cilia of the left-right organizer (LRO) during early embryonic development results in randomization of the left/right body asymmetry. Approximately half of the PCD individuals exhibit situs inversus totalis (Figure 1), referred to as Kartagener’s syndrome. 9 More rarely, other situs anomalies associated with complex congenital heart dis- ease are observed. 10 Defects underlying motile-cilia 1 Department of General Pediatrics, University Children’s Hospital Muenster, 48149 Muenster, Germany; 2 Danish PCD Centre, Pediatrics Pulmonary Ser- vice, Department of Pediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark; 3 Department of Translational Medical Sciences, Federico II University, 80131 Naples, Italy; 4 Department of Pediatrics, University of Alberta, T6G 1C9 Edmonton, Alberta, Canada; 5 Schneider Children’s Medical Center, 4920235 Petach-Tikva, Israel; 6 Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv, Israel; 7 Clinic for Pediatrics and Adolescent Medicine, University Hospital Leipzig, 04103 Leipzig, Germany; 8 Genome Research Division, Human Genetics Department, Radboud University Medical Center and Radboud Institute for Molecular Life Sciences, Geert Grooteplein Zuid 10, 6525KL Nijmegen, The Netherlands; 9 Pediatric Genetics Division, Center for Pediatrics and Adolescent Medicine, Faculty of Medicine, Freiburg University, Mathildenstrasse 1, 79112 Freiburg, Germany 10 These authors contributed equally to this work *Correspondence: heymut.omran@ukmuenster.de https://doi.org/10.1016/j.ajhg.2018.03.025. The American Journal of Human Genetics 102, 973–984, May 3, 2018 973 Ó 2018 American Society of Human Genetics.