Search

Among more than 5,000 human monogenic disorders with known causative genes, transposable element insertion of a Long Interspersed Nuclear Element 1 (LINE1, L1) is known as the mechanistic basis in only 13 genetic conditions. Meckel-Gruber syndrome is a rare ciliopathy characterized by occipital encephalocele and cystic kidney disease. Here, we document a boy with occipital encephalocele, post-axial polydactyly, and multicystic renal disease. A medical exome analysis detected a heterozygous frameshift mutation, c.4582_4583delCG p.(Arg1528Serfs*17) in CC2D2A in the maternally derived allele. The further use of a dedicated bioinformatics algorithm for detecting retrotransposon insertions led to the detection of an L1 insertion affecting exon 7 in the paternally derived allele. The complete sequencing and sequence homology analysis of the inserted L1 element showed that the L1 element was classified as L1HS (L1 human specific) and that the element had intact open reading frames in the two L1-encoded proteins. This observation ranks Meckel-Gruber syndrome as only the 14th disorder to be caused by an L1 insertion among more than 5,000 known human genetic disorders. Although a transposable element detection algorithm is not included in the current best-practice next-generation sequencing analysis, the present observation illustrates the utility of such an algorithm, which would require modest computational time and resources. Whether the seemingly infrequent recognition of L1 insertion in the pathogenesis of human genetic diseases might simply reflect a lack of appropriate detection methods remains to be seen., (© 2017 Wiley Periodicals, Inc.)

Ubiquitous in nature, cilia and flagella comprise nearly identical structures with similar functions. The most obvious example of the latter is motility: driving movement of the organism or particle flow across the epithelial surface in fixed structures. In vertebrates, such motile cilia are evident in the respiratory epithelia, ependyma, and oviducts. For over a century, non-motile cilia have been observed on the surface of most vertebrate cells but until recently their function has eluded us. Gathering evidence now points to critical roles for the mono-cilium in sensing the extracellular environment, and perturbation of this function gives rise to a predictable panoply of clinical problems. We review the common clinical phenotypes associated with ciliopathies and interrogate Online Mendelian Inheritance in Man (OMIM) to compile a comprehensive list of putative disorders in which ciliary dysfunction may play a role., (Copyright 2009 Wiley-Liss, Inc.)

Hepatorenal fibrocystic diseases (HRFCDs) are among the most common inherited human disorders. The discovery that proteins defective in the autosomal dominant and recessive polycystic kidney diseases (ADPKD and ARPKD) localize to the primary cilia and the recognition of the role these organelles play in the pathogenesis of HRFCDs led to the term "ciliopathies." While ADPKD and ARPKD are the most common ciliopathies associated with both liver and kidney disease, variable degrees of renal and/or hepatic involvement occur in many other ciliopathies, including Joubert, Bardet-Biedl, Meckel-Gruber, and oral-facial-digital syndromes. The ductal plate malformation (DPM), a developmental abnormality of the portobiliary system, is the basis of the liver disease in ciliopathies that manifest congenital hepatic fibrosis (CHF), Caroli syndrome (CS), and polycystic liver disease (PLD). Hepatocellular function remains relatively preserved in ciliopathy-associated liver diseases. The major morbidity associated with CHF is portal hypertension (PH), often leading to esophageal varices and hypersplenism. In addition, CD predisposes to recurrent cholangitis. PLD is not typically associated with PH, but may result in complications due to mass effects. The kidney pathology in ciliopathies ranges from non-functional cystic dysplastic kidneys to an isolated urinary concentration defect; the disorders contributing to this pathology, in addition to ADPKD and ARPKD, include nephronophithisis (NPHP), glomerulocystic kidney disease and medullary sponge kidneys. Decreased urinary concentration ability, resulting in polyuria and polydypsia, is the first and most common renal symptom in ciliopathies. While the majority of ADPKD, ARPKD, and NPHP patients require renal transplantation, the frequency and rate of progression to renal failure varies considerably in other ciliopathies. This review focuses on the kidney and liver disease found in the different ciliopathies., (Copyright 2009 Wiley-Liss, Inc.)

Motile cilia have long been known to play a role in processes such as cell locomotion and fluid movement whereas the functions of primary cilia have remained obscure until recent years. To date, ciliary dysfunction has been shown to be causally linked to a number of clinical manifestations that characterize the group of human disorders known as ciliopathies. This classification reflects a common or shared cellular basis and implies that it is possible to associate a series of different human conditions with ciliary dysfunction, which allows gaining insight into the cellular defect in disorders of unknown etiology solely based on phenotypic observations. Furthermore, to date we know that the cilium participates in a number of biological processes ranging from chemo- and mechanosensation to the transduction of a growing list of paracrine signaling cascades that are critical for the development and maintenance of different tissues and organs. Consequently, the primary cilium has been identified as a key structure necessary to regulate and maintain cellular and tissue homeostasis and thus its study is providing significant information to understand the pathogenesis of the different phenotypes that characterize these human conditions. Finally, the similarities between different ciliopathies at the phenotypic level are proving to be due to their shared cellular defect and also their common genetic basis. To this end, recent studies are showing that mutations in a given ciliary gene often appear involved in the pathogenesis of more than one clinical entity, complicating their genetic dissection, and hindering our ability to generate accurate genotype-phenotype correlations., (Copyright 2009 Wiley-Liss, Inc.)

Background: Lung mucociliary clearance provides the first line of defense from lung infections and is impaired in individuals who consume heavy amounts of alcohol. Previous studies have demonstrated that this alcohol-induced ciliary dysfunction occurs through impairment of nitric oxide (NO) and cyclic nucleotide-dependent kinase-signaling pathways in lung airway ciliated epithelial cells. Recent studies have established that all key elements of this alcohol-driven signaling pathway co-localize to the apical surface of the ciliated cells with the basal bodies. These findings led us to hypothesize that alcohol activates the cilia stimulation pathway at the organelle level. To test this hypothesis we performed experiments exposing isolated demembranated cilia (isolated axonemes) to alcohol and studied the effect of alcohol-stimulated ciliary motility on the pathways involved with isolated axoneme activation., Methods: Isolated demembranated cilia were prepared from bovine trachea and activated with adenosine triphosphate. Ciliary beat frequency, NO production, adenylyl and guanylyl cyclase activities, cAMP- and cGMP-dependent kinase activities were measured following exposure to biologically relevant concentrations of alcohol., Results: Alcohol rapidly stimulated axoneme beating 40% above baseline at very low concentrations of alcohol (1 to 10 mM). This activation was specific to ethanol, required the synthesis of NO, the activation of soluble adenylyl cyclase (sAC), and the activation of both cAMP- and cGMP-dependent kinases (PKA and PKG), all of which were present in the isolated organelle preparation., Conclusions: Alcohol rapidly and sequentially activates the eNOS-->NO-->GC-->cGMP-->PKG and sAC-->cAMP--> PKA dual signaling pathways in isolated airway axonemes. These findings indicate a direct effect of alcohol on airway cilia organelle function and fully recapitulate the alcohol-driven activation of cilia known to exist in vivo and in intact lung ciliated cells in vitro following brief moderate alcohol exposure. Furthermore, these findings indicate that airway cilia are exquisitely sensitive to the effects of alcohol and substantiate a key role for alcohol in the alterations of mucociliary clearance associated with even low levels of alcohol intake. We speculate that this same axoneme-based alcohol activation pathway is down regulated following long-term high alcohol exposure and that the isolated axoneme preparation provides an excellent model for studying the mechanism of alcohol-mediated cilia dysfunction.

Unlabelled: Age at diagnosis and the symptom history of children with primary ciliary dyskinesia (PCD) are described by reviewing the case notes in the paediatric PCD clinic. Mean age at diagnosis was 4.4 y despite a history of neonatal respiratory distress in 37/55 cases, situs inversus in 38/55 cases and early onset troublesome rhinitis in 42/55., Conclusion: Diagnosis of PCD is often delayed despite the presence of typical symptoms early in life. The key clinical features of unexplained neonatal respiratory distress, early onset rhinitis, situs inversus and a productive cough are highlighted, which, especially when occurring in combination, makes early referral for specific testing for PCD mandatory.

Objectives/hypothesis: To investigate the in vivo nasal ciliary beat and the ciliary ultrastructure in Down syndrome because, although in this condition an increased susceptibility to respiratory tract infections has been reported by several authors, the nature of this phenomenon is not fully understood., Study Design: Experimental study of 18 subjects with Down syndrome and 18 healthy control subjects., Methods: Ciliary beat frequency (CBF) was measured on samples of ciliated epithelium obtained from the inferior nasal turbinate; a further brushing for ultrastructural analysis was performed only in subjects showing a CBF reduction or a ciliary movement alteration., Results: The mean CBF in the group with Down syndrome was 7 +/- 2.82 Hz, and in the control subjects it was 10.94 +/- 0.65 Hz. In the same 66.6% of subjects with Down syndrome, we observed a fibrillatory movement of cilia and no metachronicity was present. Moreover, in 14 subjects with Down syndrome as hyperproduction of mucus was present. Ultrastructural evaluation at transmission election microscopy instead revealed a normal architecture of cilia., Conclusion: We attribute the nature of the mucociliary defect in Down syndrome to recurrent respiratory tract infections causing changes in mucus properties as in rheological parameters and not to a primitive defect of cilia.

Objective: Defective ciliary ultrastructure and impaired mucociliary clearance play an important role in the development of respiratory disease and sinusitis. Changes in the ciliary ultrastructure of the sinonasal epithelium have been documented in patients with primary ciliary dyskinesia. However, secondary ciliary dyskinesias and epithelial cytopathologic changes have been underappreciated as a consequence of respiratory dysfunction and chronic sinusitis., Study Design: Thirty-two patients with severe chronic sinusitis were evaluated for ciliary and epithelial abnormalities., Materials and Methods: Fourteen patients (44%) were children who underwent full allergy, sweat, and immunologic workups. Eighteen patients (56%) were adults who had severe refractory sinusitis and had failed previous sinus surgery. All patients underwent nasal epithelium biopsies of the middle turbinate and evaluation by light and transmission electron microscopy., Results: Ciliated cells were found in 23 patients (72%) with 9 patients (28%) having no cilia. Foci of normal ciliated epithelium were found in only 19% of the patients, often in epithelial invaginations. Variable numbers (usually a minor population) of cilia in 20 cases (87%) exhibited ultrastructural defects including compound cilia and microtubule and dynein arm defects. All of the patients showed variable loss of differentiated epithelial cells ranging from denuded epithelium to basal cell hyperplasia often associated with squamous metaplasia, secondary to chronic sinonasal disease. The lamina propria was often edematous with dilated capillaries, plasma cells, lymphocytes, and hyperplastic seromucous glands., Conclusions: This study demonstrates that ciliary dyskinesias are primarily the result rather than the cause of chronic sinusitis. Patients with chronic sinusitis of uncertain origin exhibit a prominent loss of differentiated epithelial cells, as well as ciliary defects, most of which are likely to be secondary to the chronic disease process. These changes slow down mucociliary clearance and lead to a vicious cycle leading to chronicity.

Objectives: Evaluate the age-dependency of ciliary beat frequency (CBF) in biopsies after ciliogenesis in culture., Study Design: Retrospective analysis of CBF and ciliary ultrastructure in biopsies and after ciliogenesis from 203 individuals, aged 3 months to 74 years., Methods: All patients with successful culture were included. Ciliogenesis was obtained using the sequential monolayer-suspension culture technique for dissociated nasal epithelial cells. CBF was measured using computerized microscope photometry. Secondary ultrastructural abnormalities were evaluated in transmission electron microscopy., Results: There was no correlation between age and CBF, in either the biopsies (7.0 +/- 2.6 Hz; n = 113) or after ciliogenesis in culture (8.1 +/- 1.3 Hz; n = 203). Even in individuals older than 70 years, CBF was normal in bioptic material (6.7 +/- 1.7 Hz) and after ciliogenesis in culture (7.9 +/- 1.0 Hz). Also, in individuals less than 1 year of age CBF was normal in biopsies as well as after ciliogenesis. CBF correlated inversely with the percentage of secondary ultrastructural abnormalities in the biopsies as seen with transmission electron microscopy: 8.1 +/- 1.8 Hz when ciliary ultrastructure was normal and 3.5 +/- 3.3 Hz in cases of severe secondary ciliary dyskinesia. After ciliogenesis in culture, ciliary ultrastructure was always normal, as was CBF., Conclusion: CBF is age independent but correlates with secondary ultrastructural abnormalities. CBF after ciliogenesis in culture is the intrinsic one.

The middle ear cavity and the eustachian tube contain a well-functioning mucociliary clearance system. To learn more about the importance of this mucociliary clearance, we studied patients with primary ciliary dyskinesia, in whom mucociliary clearance is absent. Thirty-six patients were investigated by means of a questionnaire; in 16 of these patients, otological and audiological studies could be performed. In patients with primary ciliary dyskinesia, a discrepancy was found between subjective ear complaints and the actual middle ear function. Moreover, it appeared that for the middle ear system, mucociliary clearance is of importance only in the first 3 decades of life. With aging, however, a deficient mucociliary clearance system in the middle ear and eustachian tube can be fully compensated for.

The clinical use of various tests of ciliary activity is uncertain and the purpose of this study is to assess the practical significance of the most current methods. Therefore, biopsy specimens of the nasal mucosa were investigated by means of phase contrast microscopy in 68 patients with chronic and recurrent infections of the upper airways. In 19 cases an absent or extremely weak ciliary activity could be demonstrated. Ultrastructurally, a characteristic pattern of defective dynein arms as observed in primary ciliary dyskinesia, was evident in only 3 out of these 19 patients. Measurements of the mucociliary transport velocity by means of intranasal Tc 99m labeled particles appeared to be unreliable in cases of severe nasal obstruction. In this study, phase contrast microscopy of biopsy material from the nasal respiratory epithelium appeared to have the most advantages: It is a practical and rather simple screening test in the assessment of ciliary activity.