Ciliary Structure Research Articles

A novel Cre-inducible knock-in ARL13B-tRFP fusion cilium reporter.

Cilia play a major role in the regulation of numerous signaling pathways and are essential for embryonic development. Mutations in genes affecting ciliary function can cause a variety of diseases in humans summarized as ciliopathies. To facilitate the detection and visualization of cilia in a temporal and spatial manner in mouse tissues, we generated a Cre-inducible cilium-specific reporter mouse line expressing an ARL13B-tRFP fusion protein driven by a CMV enhancer/chicken β actin promotor (pCAG) from the Hprt locus. We detected bright and specific ciliary signals by immunostainings of various mono- and multiciliated tissues and by time-lapse live-cell analysis of cultured embryos and organ explant cultures. Additionally, we monitored cilium assembly and disassembly in embryonic fibroblast cells using live-cell imaging. Thus, the ARL13B-tRFP reporter mouse strain is a valuable tool for the investigation of ciliary structure and function in a tissue-specific manner to understand processes, such as ciliary protein trafficking or cilium-dependent signaling in vitro and in vivo.

Primary ciliary dyskinesia: mechanisms and management.

Primary ciliary dyskinesia is a genetically heterogeneous disorder of motile cilia that is predominantly inherited in an autosomal-recessive fashion. It is associated with abnormal ciliary structure and/or function leading to chronic upper and lower respiratory tract infections, male infertility, and situs inversus. The estimated prevalence of primary ciliary dyskinesia is approximately one in 10,000–40,000 live births. Diagnosis depends on clinical presentation, nasal nitric oxide, high-speed video-microscopy analysis, transmission electron microscopy, genetic testing, and immunofluorescence. Here, we review its clinical features, diagnostic methods, molecular basis, and available therapies.

Nasal Nitric Oxide Measurement and a Modified PICADAR Score for the Screening of Primary Ciliary Dyskinesia in Adults with Bronchiectasis.

Background Determining the underlying diagnosis is essential for the targeted and specific treatment of bronchiectasis. Primary ciliary dyskinesia (PCD) is a rare genetic disease, which is characterized by abnormalities in ciliary structure and/or function and which may result in bronchiectasis. The disease is probably underestimated among adults with bronchiectasis due to the fact that extensive diagnostic testing is required and that the recognition of PCD is low. Objective To evaluate a feasible screening algorithm for PCD among adults with bronchiectasis. Methods Data from all patients who presented to our bronchiectasis outpatient clinic from June 2010 until July 2016 were retrospectively analysed from our database. Nasal NO (nNO) and a modified PICADAR score (PrImary CiliAry DyskinesiA Rule) were measured and compared in the two groups of PCD-bronchiectasis and non-PCD-bronchiectasis. Results 185 of 365 patients (75 males, 110 females) had a sufficient measurement of nNO concentration and complete clinical data and were eligible for analysis. The mean (SD) nNO concentration in nL/ml was significant lower in the PCD group compared to the non-PCD group (25 [31] and 227 [112] nL/min, respectively; p < 0.001). A nNO level of 77 nL/min had the best discriminative value to differentiate between the two groups. Patients with PCD had a significant higher modified PIDACAR score than patients without PCD (5 2 and 1 1, respectively [p < 0.001]). Using ROC curve analysis, the modified PICADAR score of 2 had the best discriminative value with a sensitivity of 1.00 and a specificity of 0.89. Conclusions Low nNO concentration and the modified PICADAR score are suitable and cheap screening tests for PCD in adults with bronchiectasis.

Bioinspired Ciliary Force Sensor for Robotic Platforms

The detection of small forces is of great interest in any robotic application that involves interaction with the environment (e.g., objects manipulation, physical human-robot interaction, minimally invasive surgery), since it allows the robot to detect the contacts early on and to act accordingly. In this letter, we present a sensor design inspired by the ciliary structure frequently found in nature, consisting of an array of permanently magnetized cylinders (cilia) patterned over a giant magnetoresistance sensor (GMR). When these cylinders are deformed in shape due to applied forces, the stray magnetic field variation will change the GMR sensor resistivity, thus enabling the electrical measurement of the applied force. In this letter, we present two 3 mm × 3 mm prototypes composed of an array of five cilia with 1 mm of height and 120 and 200 μm of diameter for each prototype. A minimum force of 333 μN was measured. A simulation model for determining the magnetized cylinders average stray magnetic field is also presented.

The Meckel syndrome- associated protein MKS1 functionally interacts with components of the BBSome and IFT complexes to mediate ciliary trafficking and hedgehog signaling.

The importance of primary cilia in human health is underscored by the link between ciliary dysfunction and a group of primarily recessive genetic disorders with overlapping clinical features, now known as ciliopathies. Many of the proteins encoded by ciliopathy-associated genes are components of a handful of multi-protein complexes important for the transport of cargo to the basal body and/or into the cilium. A key question is whether different complexes cooperate in cilia formation, and whether they participate in cilium assembly in conjunction with intraflagellar transport (IFT) proteins. To examine how ciliopathy protein complexes might function together, we have analyzed double mutants of an allele of the Meckel syndrome (MKS) complex protein MKS1 and the BBSome protein BBS4. We find that Mks1; Bbs4 double mutant mouse embryos exhibit exacerbated defects in Hedgehog (Hh) dependent patterning compared to either single mutant, and die by E14.5. Cells from double mutant embryos exhibit a defect in the trafficking of ARL13B, a ciliary membrane protein, resulting in disrupted ciliary structure and signaling. We also examined the relationship between the MKS complex and IFT proteins by analyzing double mutant between Mks1 and a hypomorphic allele of the IFTB component Ift172. Despite each single mutant surviving until around birth, Mks1; Ift172avc1 double mutants die at mid-gestation, and exhibit a dramatic failure of cilia formation. We also find that Mks1 interacts genetically with an allele of Dync2h1, the IFT retrograde motor. Thus, we have demonstrated that the MKS transition zone complex cooperates with the BBSome to mediate trafficking of specific trans-membrane receptors to the cilium. Moreover, the genetic interaction of Mks1 with components of IFT machinery suggests that the transition zone complex facilitates IFT to promote cilium assembly and structure.

Dynamic Remodeling of Membrane Composition Drives Cell Cycle through Primary Cilia Excision

The life cycle of a primary cilium begins in quiescence and ends prior to mitosis. In quiescent cells, the primary cilium insulates itself from contiguous dynamic membrane processes on the cell surface to function as a stable signaling apparatus. Here, we demonstrate that basal restriction of ciliary structure dynamics is established by the cilia-enriched phosphoinositide 5-phosphatase, Inpp5e. Growth induction displaces ciliary Inpp5e and accumulates phosphatidylinositol 4,5-bisphosphate in distal cilia. This change triggers otherwise-forbidden actin polymerization in primary cilia, which excises cilia tips inaprocess we call cilia decapitation. While cilia disassembly is traditionally thought to occur solely through resorption, we show that an acute loss of IFT-B through cilia decapitation precedes resorption. Finally, we propose that cilia decapitation induces mitogenic signaling and constitutes a molecular link between the cilia life cycle and cell-division cycle. This newly defined ciliary mechanism may find significance in cell proliferation control during normal development and cancer.

Silibinin negatively contributes to primary cilia length via autophagy regulated by histone deacetylase 6 in confluent mouse embryo fibroblast 3T3-L1 cells.

Primary cilium is a cellular antenna, signalling as a sensory organelle. Numerous pathological manifestation is associated with change of its length. Although the interaction between autophagy and primary cilia has been suggested, the role of autophagy in primary cilia length is largely unknown. In this study the primary cilia were immunostained and observed by using confocal fluorescence microscopy, and we found that silibinin, a natural flavonoid, shortened the length of primary cilia, meanwhile it also induced autophagy in 3T3-L1 cells. This study was designed to investigate the significance of silibinin-induced autophagy in primary ciliary structure in confluent mouse embryo fibroblast 3T3-L1 cells. Either blocking the autophagic flux with pre-treatment with the autophagy inhibitor, 3-methyladenine (3-MA), or transfection of siRNA targeting LC3 inhibited the reduction of cilia length caused by silibinin exposure. Autophagy induced by silibinin decreased expressions of the cilia-associated proteins, such as IFT88, KIF3a and Ac-tubulin, while 3-MA restored it, indicating that autophagy induced by silibinin led to a reduction of primary cilia length. Histone deacetylase 6 (HDAC6), which was suggested as a mediator of autophagy, was up-regulated by silibinin in a time-dependent manner. In addition, 3T3-L1 cells treated with siRNA against HDAC6 had a reduced autophagic level and were protected from silibinin-induced cilia shortening. Taken together, we conclude that the HDAC6-mediated autophagy negatively regulates primary cilia length during silibinin treatment and has the potential to serve as a therapeutic target for primary cilia-associated ciliopathies. These findings thus provide new information about the potential link between autophagy and primary cilia.

Effect of resveratrol on progression of polycystic kidney disease: a case of cautious optimism.

NDT Advance Access published May 17, 2016 Nephrol Dial Transplant (2016) 0: 1–4 doi: 10.1093/ndt/gfw097 In Focus Effect of resveratrol on progression of polycystic kidney disease: a case of cautious optimism Division of Nephrology and Hypertension, University of California, Irvine, 333 City Blvd West, Orange, CA 92868, USA and 2 Long Beach VA Healthcare System, Nephrology Section, Long Beach, CA, USA Correspondence and offprint requests to: Hamid Moradi; E-mail: hmoradi@uci.edu Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited genetic cause of chronic kidney disease, af- fecting 1 in 500 individuals in the USA. In addition, ADPKD is the most common genetic cause of end-stage renal disease (ESRD), accounting for ∼7–10% of patients on renal replace- ment therapy [1]. It is characterized by the development of fluid-filled cysts in the renal tubules and their progressive en- largement over time leading to the distortion of renal tissue and ongoing kidney damage and culminating in ESRD [2, 3]. At the molecular level, ADPKD is caused by mutations in the PKD1 (85%) or PKD2 (15%) genes, which encode the cilia-associated polycystin-1 (PC1) and polycystin-2 (PC2) pro- teins [4]. PC1 and PC2 are membrane proteins that are located in the primary cilia of the tubular epithelial cells, and while the ligand for PC1 has not been identified, PC2 is most likely a non- selective calcium channel [2, 3]. There are multiple mechan- isms by which mutations in the PKD1 and PKD2 genes result in cystogenesis, including increased cell proliferation, enhanced fluid secretion, abnormal cell–matrix interaction, alterations in cell polarity and abnormal ciliary structure and function [2]. However, there are also several nongenetic pathways that can contribute to the progression and modify the severity of ADPKD. This is evidenced by the fact that patients with ADPKD have large intrafamilial variability in renal function even between monozygotic twins and siblings [5]. In addition, in monozygotic twins, there can be significant differences in the age at which ESRD is reached, thereby highlighting the role of nonhereditary pathways in ADPKD-associated renal injury and progression of disease [5]. These include pathways related to growth factor and cytokine signaling [6]. The importance of in- flammation and cytokine signaling in PKD has been established in numerous studies over the past few decades. Gardner et al. [7] noted high concentrations of inflammatory chemokines and © The Author 2016. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. cytokines in the cyst fluid from patients with ADPKD. Cowley et al. [8] subsequently demonstrated that increased expression of monocyte chemoattractant protein-1 (MCP-1) was accom- panied by accumulation of macrophages in the kidneys of rats with ADPKD. It is now known that MCP-1 is present in the urine of patients with ADPKD and that high levels of urinary MCP-1 correlate with the rate of cyst growth and progression of disease [9, 10]. In line with these discoveries, large numbers of activated macrophages have been found around renal cysts in animal models of ADPKD whose depletion inhibited epithelial cell proliferation and cyst growth and improved renal function [11]. Furthermore, Swenson-Fields et al. [12] demonstrated that increased numbers of macrophages expressing the M2 marker CD163 are also present in the interstitium of kidneys of patients with both AD and autosomal recessive PKD, some of which are in close proximity to the cysts. In turn, the cyst epithelial cells stimulated macrophage differentiation toward a distinct M2-like phenotype that, based on in vitro studies, pro- moted proliferation and microcyst formation. Furthermore, re- cent studies have demonstrated that macrophage migration inhibitory factor (MIF) is upregulated in the epithelial cells lining renal cysts and that this protein accumulates in the cyst fluid of patients with ADPKD [13]. MIF was found to be a key regulator of cyst growth in ADPKD via several converging mechanisms, including cytokine signaling. It was shown that MIF-dependent macrophage recruitment was associated with increased MCP-1 and tumor necrosis factor α (TNF-α) production, which in turn increased expression of MIF. Hence, a positive feedback loop between inflammation, inflam- matory cytokines and MIF was identified, with the end result being progression of the disease [13]. Therefore, besides the gen- etic abnormalities that instigate the underlying disease in ADPKD, inflammation, macrophage activation, differentiation Downloaded from http://ndt.oxfordjournals.org/ at University of California, Irvine on May 18, 2016 Hamid Moradi 1,2 and Nosratola D. Vaziri 2

Cryo-Electron Tomography Provides a New Window into Ciliary Structure and Function

Cilia and flagella are conserved and ubiquitous eukaryotic organelles that are composed of more than 600 different proteins and have important biological roles in motility and sensation. The beating of motile cilia and flagella is driven by conformational changes of dynein motors that are coordinated by regulatory complexes. However, the mechanism(s) by which flagellar motility is generated and regulated are largely unknown. We use cryo-electron tomography, subtomogram averaging, molecular tagging and classification analyses to visualize the three-dimensional structures of intact wild-type and mutant flagella, and dissect the organization of key macromolecular complexes. We also study active (beating) flagella that were rapidly frozen to resolve the different conformations of these complexes and identify distinct conformations for different axonemal dyneins and other structures, many of which showing bend direction dependent distributions. Our comprehensive analyses combined with biochemical investigations provides a new understanding of the distinct roles played by various dyneins and regulatory complexes in the motility of cilia and flagella, and suggests critical modifications to previous hypotheses for the molecular mechanisms underlying their motility.

Cellular Mechanisms of Ciliary Length Control.

Cilia and flagella are evolutionarily conserved, membrane-bound, microtubule-based organelles on the surface of most eukaryotic cells. They play important roles in coordinating a variety of signaling pathways during growth, development, cell mobility, and tissue homeostasis. Defects in ciliary structure or function are associated with multiple human disorders called ciliopathies. These diseases affect diverse tissues, including, but not limited to the eyes, kidneys, brain, and lungs. Many processes must be coordinated simultaneously in order to initiate ciliogenesis. These include cell cycle, vesicular trafficking, and axonemal extension. Centrioles play a central role in both cell cycle progression and ciliogenesis, making the transition between basal bodies and mitotic spindle organizers integral to both processes. The maturation of centrioles involves a functional shift from cell division toward cilium nucleation which takes place concurrently with its migration and fusion to the plasma membrane. Several proteinaceous structures of the distal appendages in mother centrioles are required for this docking process. Ciliary assembly and maintenance requires a precise balance between two indispensable processes; so called assembly and disassembly. The interplay between them determines the length of the resulting cilia. These processes require a highly conserved transport system to provide the necessary substances at the tips of the cilia and to recycle ciliary turnover products to the base using a based microtubule intraflagellar transport (IFT) system. In this review; we discuss the stages of ciliogenesis as well as mechanisms controlling the lengths of assembled cilia.

Induction of Functional 3D Ciliary Epithelium-Like Structure From Mouse Induced Pluripotent Stem Cells.

To generate ciliary epithelium (CE) from mouse induced pluripotent stem (iPS) cells. Recently, a protocol for self-organizing optic cup morphogenesis in three-dimensional culture was reported, and it was suggested that ocular tissue derived from neural ectoderm could be differentiated. We demonstrated that a CE-like double-layered structure could be induced in simple culture by using a modified Eiraku differentiation protocol. Differentiation of a CE-like double-layered structure could be promoted by glycogen synthase kinase 3β (GSK-3β) inhibitor. Connexin43 and aquaporin1 were expressed in both thin layers, and induced CE-like cells expressed ciliary marker genes, such as cyclinD2, zic1, tgfb2, aldh1a3, wfdc1, otx1, BMP4, and BMP7. Increases in cytoplasmic and nuclear β-catenin in aggregates of the CE-like double-layered structure were confirmed by Western blot analysis. In addition, tankyrase inhibitor prevented the induction of the CE-like double-layered structure by GSK-3β inhibitor. Dye movement from pigmented cells to nonpigmented cells in the mouse iPS cell-derived CE-like structure was observed in a fluid movement experiment, consistent with the physiological function of CE in vivo. We could differentiate CE from mouse iPS cells in the present study. In the future, we hope that this CE-like complex will become useful as a graft for transplantation therapy in pathologic ocular hypotension due to CE dysfunction, and as a screening tool for the development of drugs for diseases associated with CE function.

Gene editing of DNAH11 restores normal cilia motility in primary ciliary dyskinesia

BackgroundPrimary ciliary dyskinesia (PCD) is a rare autosomal recessive genetic disorder characterised by dysfunction of motile cilia. Ciliary dysmotility causes poor mucociliary clearance and leads to impairment of pulmonary function...

Conserved Genetic Interactions between Ciliopathy Complexes Cooperatively Support Ciliogenesis and Ciliary Signaling.

Mutations in genes encoding cilia proteins cause human ciliopathies, diverse disorders affecting many tissues. Individual genes can be linked to ciliopathies with dramatically different phenotypes, suggesting that genetic modifiers may participate in their pathogenesis. The ciliary transition zone contains two protein complexes affected in the ciliopathies Meckel syndrome (MKS) and nephronophthisis (NPHP). The BBSome is a third protein complex, affected in the ciliopathy Bardet-Biedl syndrome (BBS). We tested whether mutations in MKS, NPHP and BBS complex genes modify the phenotypic consequences of one another in both C. elegans and mice. To this end, we identified TCTN-1, the C. elegans ortholog of vertebrate MKS complex components called Tectonics, as an evolutionarily conserved transition zone protein. Neither disruption of TCTN-1 alone or together with MKS complex components abrogated ciliary structure in C. elegans. In contrast, disruption of TCTN-1 together with either of two NPHP complex components, NPHP-1 or NPHP-4, compromised ciliary structure. Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did. As in nematodes, disrupting two components of the mouse MKS complex did not cause additive phenotypes compared to single mutants. However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1. Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes.

The Expression and Cellular Localization of Galectin-1 and Galectin-3 in the Fallopian Tube Are Altered in Women with Tubal Ectopic Pregnancy

Galectin-1 and galectin-3 are abundantly expressed at implantation sites in the uterus, suggesting their involvement in the establishment of pregnancy. In this study, we examined the expression and localization of galectin-1 and galectin-3 in fallopian tubes from nonpregnant women, and in those presenting with tubal ectopic pregnancy. There was no significant difference in the expression of either galectin-1 (LGALS1) or galectin-3 (LGALS3) transcripts in the fallopian tube across the menstrual cycle. Their expressions in the fallopian tube were inversely correlated to each other (r = −0.5134, p < 0.0001) and differentially localized. Galectin-1 protein was abundant in the stroma of nonpregnant fallopian tubes, whereas galectin-3 was mainly localized to the epithelium, notably to the cilia of ciliated cells and the apical cytoplasm of secretory cells. In ectopic pregnancies, LGALS3 expression was significantly reduced (p < 0.0001), but LGALS1 expression did not change when compared to nonpregnant fallopian tubes collected during the mid-secretory phase. The percentage of fallopian tube epithelial cells expressing galectin-3 in cilia tended to be reduced (p = 0.0685), with an accompanying loss of a normal ciliary structure, while nuclear galectin-3 increased (p < 0.05) in ectopic pregnancies. Epithelial immunostaining for galectin-1 tended to be elevated in fallopian tubes from women with ectopic pregnancy. Coculture of human trophoblast origin SW71 cells significantly increased LGALS1 expression in human fallopian tube epithelial OE-E6/E7 cells, suggesting that trophoblast-derived products regulate LGALS1 expression in the oviductal epithelium. These findings imply a differential contribution of galectin-1 and galectin-3 in the homeostasis of human fallopian tubes and in the pathophysiology of ectopic pregnancy.

Alström syndrome: current perspectives.

Alström syndrome (ALMS) is a rare genetic disorder that has been included in the ciliopathies group, in the last few years. Ciliopathies are a growing group of diseases associated with defects in ciliary structure and function. The development of more powerful genetic approaches has been replaced the strategies to follow for getting a successful molecular diagnosis for these patients, especially for those without the typical ALMS phenotype. In an effort to deepen the understanding of the pathogenesis of ALMS disease, much work has been done, in order to establish the biological implication of ALMS1 protein, which is still being elucidated. In addition to its role in ciliary function and structure maintenance, this protein has been implicated in intracellular trafficking, regulation of cilia signaling pathways, and cellular differentiation, among others. All these progresses will lead to identifying therapeutic targets, thus opening the way to future personalized therapies for human ciliopathies.

Diagnosis of primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a genetic disorder of ciliary structure or function. It results in mucus accumulation and bacterial colonization of the respiratory tract which leads to chronic upper and lower airway infections, organ laterality defects, and fertility problems. We review the respiratory signs and symptoms of PCD, as well as the screening tests for and diagnostic investigation of the disease, together with details related to ciliary function, ciliary ultrastructure, and genetic studies. In addition, we describe the difficulties in diagnosing PCD by means of transmission electron microscopy, as well as describing patient follow-up procedures.

Live Imaging of the Ependymal Cilia in the Lateral Ventricles of the Mouse Brain.

Multiciliated ependymal cells line the ventricles in the adult brain. Abnormal function or structure of ependymal cilia is associated with various neurological deficits. The current ex vivo live imaging of motile ependymal cilia technique allows for a detailed study of ciliary dynamics following several steps. These steps include: mice euthanasia with carbon dioxide according to protocols of The University of Toledo's Institutional Animal Care and Use Committee (IACUC); craniectomy followed by brain removal and sagittal brain dissection with a vibratome or sharp blade to obtain very thin sections through the brain lateral ventricles, where the ependymal cilia can be visualized. Incubation of the brain's slices in a customized glass-bottom plate containing Dulbecco's Modified Eagle's Medium (DMEM)/High-Glucose at 37 °C in the presence of 95%/5% O2/CO2 mixture is essential to keep the tissue alive during the experiment. A video of the cilia beating is then recorded using a high-resolution differential interference contrast microscope. The video is then analyzed frame by frame to calculate the ciliary beating frequency. This allows distinct classification of the ependymal cells into three categories or types based on their ciliary beating frequency and angle. Furthermore, this technique allows the use of high-speed fluorescence imaging analysis to characterize the unique intracellular calcium oscillation properties of ependymal cells as well as the effect of pharmacological agents on the calcium oscillations and the ciliary beating frequency. In addition, this technique is suitable for immunofluorescence imaging for ciliary structure and ciliary protein localization studies. This is particularly important in disease diagnosis and phenotype studies. The main limitation of the technique is attributed to the decrease in live motile cilia movement as the brain tissue starts to die.

GPs Meet Rare Lung Disorders Task Force factsheet: primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a rare, autosomal recessive disease of abnormalities of ciliary structure and function. The result is impaired mucociliary clearance, causing a variety of respiratory symptoms, and likely progression to bronchiectasis in most cases. Situs anomalies are present in nearly 50% of cases.

Peripheral vestibular dysfunction in patients with primary ciliary dyskinesia: abnormal otoconial development?

Patients with primary ciliary dyskinesia (PCD) have absent or reduced otoconial function compared to the normal population. Investigations in zebrafish show that ciliation is important for the development of the otolith organs, but this has never been evaluated in humans. PCD is a congenital defect of ciliary structure. We undertook a pilot study to determine whether patients with PCD have absent or reduced otoconial function compared to the normal population. Vestibular function testing, including utricular centrifugation (UCF) testing, vestibular evoked myogenic potentials (VEMPs), and electronystagmography, was undertaken in five patients with known PCD. Patients also completed validated questionnaires regarding subjective balance function and symptoms. There were markedly reduced or unobtainable VEMPs bilaterally in three of the five subjects and unilaterally in the remaining two subjects. No subject had a pathological UCF asymmetry, but three subjects showed utricular abnormalities. The vestibulo-ocular reflex (VOR) at 0.25 Hz sinusoidal rotation was normal in all subjects. There were no subjective dizzy symptoms or balance issues. We speculate that the reduced saccular and utricular function in PCD patients observed in this pilot study suggests a relationship between cilia structure and/or motility, and otoconia seeding and/or positioning. Further investigation is warranted.

Variation in DNAH1 may contribute to primary ciliary dyskinesia

BackgroundPrimary Ciliary Dyskinesia (PCD) is a genetically heterogeneous ciliopathy caused by ultrastructural defects in ciliary or flagellar structure and is characterized by a number of clinical symptoms including recurrent respiratory infections progressing to permanent lung damage and infertility.Case presentationHere we describe our search to delineate the molecular basis in two affected sisters with clinically diagnosed PCD from a consanguineous Saudi Arabian family, in which all known genes have been excluded. A homozygosity mapping-based approach was utilized that ultimately identified one single affected-shared region of homozygosity using 10 additional unaffected family members. A plausible candidate gene was directly sequenced and analyzed for mutations. A novel homozygous missense aberration (p.Lys1154Gln) was identified in both sisters in the DNAH1 gene that segregated completely with the disease phenotype. Further confirmation of this interesting variant was provided by exome-wide analysis in the proband.ConclusionMolecular variation in DNAH1 may play a role in PCD and its potential contribution should be considered in patients where all known genes are excluded.Electronic supplementary materialThe online version of this article (doi:10.1186/s12881-015-0162-5) contains supplementary material, which is available to authorized users.