Variant Of Primary Ciliary Dyskinesia Research Articles

Gene dosage of independent dynein arm motor preassembly factors influences cilia assembly in Chlamydomonas reinhardtii.

Motile cilia assembly utilizes over 800 structural and cytoplasmic proteins. Variants in approximately 58 genes cause primary ciliary dyskinesia (PCD) in humans, including the dynein arm (pre)assembly factor (DNAAF) gene DNAAF4. In humans, outer dynein arms (ODAs) and inner dynein arms (IDAs) fail to assemble motile cilia when DNAAF4 function is disrupted. In Chlamydomonas reinhardtii, a ciliated unicellular alga, the DNAAF4 ortholog is called PF23. The pf23-1 mutant assembles short cilia and lacks IDAs, but partially retains ODAs. The cilia of a new null allele (pf23-4) completely lack ODAs and IDAs and are even shorter than cilia from pf23-1. In addition, PF23 plays a role in the cytoplasmic modification of IC138, a protein of the two-headed IDA (I1/f). As most PCD variants in humans are recessive, we sought to test if heterozygosity at two genes affects ciliary function using a second-site non-complementation (SSNC) screening approach. We asked if phenotypes were observed in diploids with pairwise heterozygous combinations of 21 well-characterized ciliary mutant Chlamydomonas strains. Vegetative cultures of single and double heterozygous diploid cells did not show SSNC for motility phenotypes. When protein synthesis is inhibited, wild-type Chlamydomonas cells utilize the pool of cytoplasmic proteins to assemble half-length cilia. In this sensitized assay, 8 double heterozygous diploids with pf23 and other DNAAF mutations show SSNC; they assemble shorter cilia than wild-type. In contrast, double heterozygosity of the other 203 strains showed no effect on ciliary assembly. Immunoblots of diploids heterozygous for pf23 and wdr92 or oda8 show that PF23 is reduced by half in these strains, and that PF23 dosage affects phenotype severity. Reductions in PF23 and another DNAAF in diploids affect the ability to assemble ODAs and IDAs and impedes ciliary assembly. Thus, dosage of multiple DNAAFs is an important factor in cilia assembly and regeneration.

A rare variant of primary ciliary dyskinesia in combination with hereditary hemorrhagic telangiectasia type 1: a case from practice

Primary ciliary dyskinesia (PCD) is a rare genetic disease belonging to the group of ciliopathies. The disease develops because a defect in the ultrastructure of the epithelial cilia in the respiratory tract and similar structures (sperm flagella, villi of the fallopian tubes, ventricular ependyma, etc.) disturbs their motor function. Currently, various clinical and genetic variants of the disease are distinguished, increasing the effectiveness of dynamic examination and treatment.Aim. In this article, we describe a patient with a rare variant of PCD that we identified in combination with a mutation in the ENG gene responsible for the development of hereditary hemorrhagic telangiectasia type 1 (HHT-1). HHT-1 is a rare hereditary disease that manifests as various vascular dysplasias, including arteriovenous malformations (AVM) in the lungs, which can significantly worsen the course of the disease and be a predictor of an unfavorable outcome.Conclusion. The presented case demonstrates a combination of two rare genetic diseases in a child. The uniqueness of the case also lies in the fact that the identified rare mutation in the DRC1 gene responsible for the development of PCD is not associated with a loss of motility of the cilia of the ciliated epithelium, which makes the testing and the correct diagnosis even more difficult.

Characteristic genetic spectrum of primary ciliary dyskinesia in Japanese patients and global ethnic heterogeneity: population-based genomic variation database analysis.

Primary ciliary dyskinesia (PCD) is a hereditary disease caused by pathogenic variants in genes associated with motile cilia. Some variants responsible for PCD are reported to be ethnic-specific or geographical-specific. To identify the responsible PCD variants of Japanese PCD patients, we performed next-generation sequencing of a panel of 32 PCD genes or whole-exome sequencing in 26 newly identified Japanese PCD families. We then combined their genetic data with those from 40 Japanese PCD families reported previously, for an overall analysis of 66 unrelated Japanese PCD families. We conducted Genome Aggregation Database and TogoVar database analyses to reveal the PCD genetic spectrum of the Japanese population and compare with other ethnic groups worldwide. We identified 22 unreported variants among the 31 patients in the 26 newly identified PCD families, including 17 deleterious variants estimated to cause lack of transcription or nonsense-mediated mRNA decay and 5 missense mutations. In all 76 PCD patients from the 66 Japanese families, we identified 53 variants on 141 alleles in total. Copy number variation in DRC1 is the most frequent variant in Japanese PCD patients, followed by DNAH5 c.9018C>T. We found 30 variants specific to the Japanese population, of which 22 are novel. Furthermore, 11 responsible variants in the Japanese PCD patients are common in East Asian populations, while some variants are more frequent in other ethnic groups. In conclusion, PCD is genetically heterogeneous between different ethnicities, and Japanese PCD patients have a characteristic genetic spectrum.

The Genetics of Primary Ciliary Dyskinesia in Puerto Rico.

Primary ciliary dyskinesia (PCD) has been linked to more than 50 genes that cause a spectrum of clinical symptoms, including newborn respiratory distress, sinopulmonary infections, and laterality abnormalities. Although the RSPH4A (c.921+3_6delAAGT) pathogenic variant has been related to Hispanic groups with Puerto Rican ancestry, it is uncertain how frequently other PCD-implicated genes are present on the island. A retrospective chart review of n = 127 genetic reports from Puerto Rican subjects who underwent genetic screening for PCD variants was conducted from 2018 to 2022. Of 127 subjects, 29.1% subjects presented PCD pathogenic variants, and 13.4% were homozygous for the RSPH4A (c.921+3_6delAAGT) founder mutation. The most common pathogenic variants were in RSPH4A and ZMYND10 genes. A description of the frequency and geographic distribution of implicated PCD pathogenic variants in Puerto Rico is presented. Our findings reconfirm that the presence of PCD in Puerto Rico is predominantly due to a founder pathogenic variant in the RSPH4A (c.921+3_6delAAGT) splice site. Understanding the frequency of PCD genetic variants in Puerto Rico is essential to map a future genotype-phenotype PCD spectrum in Puerto Rican Hispanics with a heterogeneous ancestry.

Axonemal Symmetry Break, a New Ultrastructural Diagnostic Tool for Primary Ciliary Dyskinesia?

Diagnosis testing for primary ciliary dyskinesia (PCD) requires a combination of investigations that includes study of ciliary beat pattern by high-speed video-microscopy, genetic testing and assessment of the ciliary ultrastructure by transmission electron microscopy (TEM). Historically, TEM was considered to be the “gold standard” for the diagnosis of PCD. However, with the advances in molecular genetic techniques, an increasing number of PCD variants show normal ultrastructure and cannot be diagnosed by TEM. During ultrastructural assessment of ciliary biopsies of patients with suspicion of PCD, we observed an axonemal defect not previously described that affects peripheral doublets tilting. To further characterize this defect of unknown significance, we studied the ciliary axonemes by TEM from both PCD-confirmed patients and patients with other sino-pulmonary diseases. We detected peripheral doublets tilting in all the PCD patients, without any significant difference in the distribution of ciliary beat pattern or mutated gene. This defect was also present in those patients with normal ultrastructure PCD subtypes. We believe that the performance of axonemal asymmetry analysis would be helpful to enhance diagnosis of PCD.

A Study on the Genetics of Primary Ciliary Dyskinesia.

Primary ciliary dyskinesia (PCD) is a poorly understood disorder. It is primarily autosomal recessive and is prevalent in tribal communities of the United Arab Emirates due to consanguineous marriages. This retrospective study aimed to assess the pathogenicity of the genetic variants of PCD in indigenous patients with significant clinical respiratory problems. Pathogenicity scores of variants obtained from the chart review were consolidated using the Ensembl Variant Effect Predictor. The multidimensional dataset of scores was clustered into three groups based on their pathogenicity. Sequence alignment and the Jensen–Shannon Divergence (JSD) were generated to evaluate the amino acid conservation at the site of the variation. One-hundred and twelve variants of 28 genes linked to PCD were identified in 66 patients. Twenty-two variants were double heterozygous, two triple heterozygous, and seven homozygous. Of the thirteen novel variants, two, c.11839 + 1G > A in dynein, axonemal, heavy chain 11 (DNAH11) and p.Lys92Trpfs in dynein, axonemal, intermediate chain 1 (DNAI1) were associated with dextrocardia with situs inversus, and one, p.Gly21Val in coiled-coil domain-containing protein 40 (CCDC40), with absent inner dynein arms. Homozygous C1orf127:p.Arg113Ter (rs558323413) was also associated with laterality defects in two related patients. The majority of variants were missense involving conserved residues with a median JSD score of 0.747. Homology models of two deleterious variants in the stalk of DNAH11, p.Gly3102Asp and p.Leu3127Arg, revealed structural importance of the conserved glycine and leucine. These results define potentially damaging PCD variants in the region. Future studies, however, are needed to fully comprehend the genetic underpinnings of PCD.

SPEF2- and HYDIN-Mutant Cilia Lack the Central Pair-associated Protein SPEF2, Aiding Primary Ciliary Dyskinesia Diagnostics.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous chronic destructive airway disease. PCD is traditionally diagnosed by nasal nitric oxide measurement, analysis of ciliary beating, transmission electron microscopy (TEM), and/or genetic testing. In most genetic PCD variants, laterality defects can occur. However, it is difficult to establish a diagnosis in individuals with PCD and central pair (CP) defects, and alternative strategies are required because of very subtle ciliary beating abnormalities, a normal ciliary ultrastructure, and normal situs composition. Mutations in HYDIN are known to cause CP defects, but the genetic analysis of HYDIN variants is confounded by the pseudogene HYDIN2, which is almost identical in terms of intron/exon structure. We have previously shown that several types of PCD can be diagnosed via immunofluorescence (IF) microscopy analyses. Here, using IF microscopy, we demonstrated that in individuals with PCD and CP defects, the CP-associated protein SPEF2 is absent in HYDIN-mutant cells, revealing its dependence on functional HYDIN. Next, we performed IF analyses of SPEF2 in respiratory cells from 189 individuals with suspected PCD and situs solitus. Forty-one of the 189 individuals had undetectable SPEF2 and were subjected to a genetic analysis, which revealed one novel loss-of-function mutation in SPEF2 and three reported and 13 novel HYDIN mutations in 15 individuals. The remaining 25 individuals are good candidates for new, as-yet uncharacterized PCD variants that affect the CP apparatus. SPEF2 mutations have been associated with male infertility but have not previously been identified to cause PCD. We identified a mutation of SPEF2 that is causative for PCD with a CP defect. We conclude that SPEF2 IF analyses can facilitate the detection of CP defects and evaluation of the pathogenicity of HYDIN variants, thus aiding the molecular diagnosis of CP defects.

AKNA Frameshift Variant in Three Dogs with Recurrent Inflammatory Pulmonary Disease.

We investigated three related Rough Collies with recurrent inflammatory pulmonary disease. The clinical symptoms were similar to primary ciliary dyskinesia (PCD). However, the affected dogs did not carry any known pathogenic PCD variants. Pedigree analysis suggested a recessive mode of inheritance. Combined linkage and homozygosity mapping in three cases and seven non-affected family members delineated 19 critical intervals on 10 chromosomes comprising a total of 99 Mb. The genome of one affected dog was sequenced and compared to 601 control genomes. We detected only a single private homozygous protein-changing variant in the critical intervals. The detected variant was a 4 bp deletion, c.2717_2720delACAG, in the AKNA gene encoding the AT-hook transcription factor. It causes a frame-shift introducing a premature stop codon and truncates 37% of the open reading frame, p.(Asp906Alafs*173). We genotyped 88 Rough Collies consisting of family members and unrelated individuals. All three available cases were homozygous for the mutant allele and all 85 non-affected dogs were either homozygous wildtype (n = 67) or heterozygous (n = 18). AKNA modulates inflammatory immune responses. Akna−/− knockout mice die shortly after birth due to systemic autoimmune inflammatory processes including lung inflammation that is accompanied by enhanced leukocyte infiltration and alveolar destruction. The perfect genotype-phenotype association and the comparative functional data strongly suggest that the detected AKNA:c.2717_2720delACAG variant caused the observed severe airway inflammation in the investigated dogs. Our findings enable genetic testing, which can be used to avoid the unintentional breeding of affected puppies.

Amylose rénale révélant un syndrome de Kartagener

Kartagener's syndrome is a rare disease. It is a clinical variant of primary ciliary dyskinesia. It combines a situs inversus, chronic sinusitis and bronchiectasis. Glomerulopathies associated with this syndrome are rarely reported. We report the case of Kartagener's syndrome in a patient diagnosed at the age of 37 years with renal amyloidosis.

Immunofluorescence microscopy (IFM) analysis of primary ciliary dyskinesia (PCD) patients with suspected inner dynein arm defects (IDA)

Primary ciliary dyskinesia (PCD), characterized by abnormal motility of cilia or flagella, is caused by defects of structural components such as inner dynein arms (IDAs). Recently high-speed videomicroscopy has substituted transmission electron microscopy (TEM) analysis as the “gold standard” for diagnosis. However, TEM is still the most widely used diagnostic tool in many countries. A recent study reported that isolated IDA defects is the most frequent (> 50%) ciliary defect in PCD, as detected by TEM (Theegarten, 2011). IFM analysis has shown in several studies that it can ascertain diagnosis such as in PCD variants caused by DNAH5, DNAI1, DNAI2, KTU, LRRC50, CCDC39 and CCDC40 mutations. IFM can provide a complete view of the ciliary axoneme and identify “partial” axonemal defects which may be misinterpreted by TEM (e.g. present in KTU mutant cilia). Here we performed IFM analysis of known PCD patients to identify the composition of dynein arm defects, including IDAs. Using antibodies specific to the IDA marker DNALI1, we determined that the frequency of isolated IDA defects is unexpected low (thus far, only 12 of ~800 PCD patients, ~1.5%). In contrast, we observe that IDA defects usually accompany DRC defects (absent/abnormal Gas11) or ODA defects (absent/abnormal DNAH5). Because the DNALI1 antibody is targeted against only 3 IDA isoforms out of 7, we are currently screening additional IDA-specific antibodies for IFM analysis to target the other IDA sub-types which escaped our analysis. However, our results suggest the percentage of isolated IDA defects might be lower than previously expected.

A Rare Cause of Adult Bronchiectasis

INTRODUCTION: The etiology of bronchiectasis may be idiopathic in up to one half of adults. Consideration of Primary Ciliary Dyskinesia (PCD) may not be considered in adults without dextrocardia. We present a subject with bronchiectasis with PCD and central pair absence, a rare variant of PCD not previously diagnosed at such a late age.

Review of respiratory impact in oesophageal atresia

Primary ciliary dyskinesia (PCD) is characterized by recurrent respiratory tract infections due to reduced mucociliary clearance caused by dysfunction of motile cilia. It is an autosomal recessive disorder, approximately with a situs inversus totalis (Kartagener syndrome) in about 50% of cases. There is a considerable genetic heterogeneity for PCD and several genetic defects have been identified in PCD (DNAH5, DNAH11, DNAI1, DNAI2, TXNDC3, LRRC50, KTU, RSPH4A, RSPH9, OFD1, RPGR, CCDC39, CCDC40). PCD does not only cause recurrent respiratory tract infections (rhino-sinusitis, bronchitis and bronchiectasis) due to reduced airway clearence, but is also associated with other medical disorders. Male infertility is a widely recognized medical condition in PCD. Approximately half of the men with PCD are infertile caused by poor sperm mobility. Interestingly, in the female reproductive system multiciliated motile cilia line the oviducts. Therefore ciliary dyskinesia of oviductal cilia has been speculated to be a cause of infertility in women with PCD. Likewise, an increased risk of ectopic pregnancy has been postulated for PCD female patients. However, the incidence of infertility and ectopic pregnancy has not yet been investigated systematically and therefore the role of dyskinesia of oviductal cilia is still a matter of debate. To address this important question, we performed a systematic survey of our female patients with PCD to study the incidence of infertility and gestational abnormalities. Therefore we searched our PCD database for information on pregnancies and births of adult female PCD patients. Here we report female patients with genetically proven PCD variants, which gave birth to healthy offspring. This finding indicates that the beating of oviduct cilia is not essential for fertilization of the egg.

The coiled-coil domain containing protein CCDC40 is essential for motile cilia function and left-right axis formation

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous autosomal recessive disorder characterized by recurrent infections of the respiratory tract associated with the abnormal function of motile cilia. Approximately half of individuals with PCD also have alterations in the left-right organization of their internal organ positioning, including situs inversus and situs ambiguous (Kartagener's syndrome). Here, we identify an uncharacterized coiled-coil domain containing a protein, CCDC40, essential for correct left-right patterning in mouse, zebrafish and human. In mouse and zebrafish, Ccdc40 is expressed in tissues that contain motile cilia, and mutations in Ccdc40 result in cilia with reduced ranges of motility. We further show that CCDC40 mutations in humans result in a variant of PCD characterized by misplacement of the central pair of microtubules and defective assembly of inner dynein arms and dynein regulatory complexes. CCDC40 localizes to motile cilia and the apical cytoplasm and is required for axonemal recruitment of CCDC39, disruption of which underlies a similar variant of PCD.

LUNG ABSCESS WITH PSEUDOMONAS AERUGINOSA, MYCOBACTERIUM AVIUM COMPLEX, AND NOCARDIA SP IN A PATIENT WITH KARTAGENER'S SYNDROME

INTRODUCTION: Kartagener's syndrome (KS) is a variant of primary ciliary dyskinesia (PCD). It is an autosomal recessive disease characterized by situs inversus, sinusitis and bronchiectasis. Patients with KS develop chronic and recurrent infections, typically suffering from bronchitis, pneumonia, hemoptysis, sinusitis, and infertility. We present a case of KS with lung abscess caused by Pseudomonas aeruginosa (P. aeruginosa), Mycobacterium avium intracellulare complex (MAC) and Nocardia species (spp).

Kartagener's syndrome and polycystic kidney disease

Sir, Kartagener's syndrome (KS) is a clinical variant of primary ciliary dyskinesia (PCD) involving situs inversus associated with chronic airway infections [1]. Ciliopathy has now become recognized as a multisystem disease, of which PCD is an important subgroup. Other known ciliopathies include Bardet–Biedl syndrome, polycystic kidney and liver disease, nephronophthisis, Alstrom syndrome, Meckel–Gruber syndrome and some forms of retinal degeneration [2,3]. We report a patient with KS and polycystic kidney disease, presenting with severe renal failure. A 25-year-old woman who presented with fever, weakness, nausea, cough, dyspnoea, poor general condition and respiratory distress was admitted to our hospital. The patient was diagnosed 15 years previously with KS. On physical examination, blood pressure was 120/ 80 mmHg, heart rate was 117 beats/min and respiratory rate was 22 breaths/min. Heart sounds were distant and deep on cardiac auscultation. Bilateral crackles were determined in lungs. Her laboratory findings were as follows: serum sodium 112 mmol/l, chlorine 77 mmol/l, urea 442 mg/dl, creatinine 7.5 mg/dl, haemoglobin 6.5 g/dl, leucocytes 30 000, arterial blood gas pH 7.1, bicarbonate 8 mmol/l, pCO2 22 mmHg, C-reactive protein (CRP) 41 mg/l. Due to poor general condition of the patient, with acidosis, haemodialysis was started. Ultrasonographic examination of the abdomen revealed the situs inversus and polycystic kidney disease. The CT of the abdomen and thorax CT was performed (Figures ​(Figures11 and ​and22). Fig. 1 Bronchiectasis and dextrocardia in thorax CT. Fig. 2 Polycystic kidney in abdominal CT. To our knowledge, this is the first case of KS and polycystic kidney disease reported in the literature. Conflict of interest statement. None declared.

Ciliary ultrastructure in two sisters with Kartagener's syndrome

Kartagener's syndrome (KS) is a clinical variant of primary ciliary dyskinesia involving situs inversus associated with chronic airway infections. We studied two sisters; the elder one had dextrocardia and scoliosis, and the younger one had situs inversus of the lung, liver, and stomach as well as dextrocardia. Both patients had chronic sinusitis and chronic bronchitis with bronchiectasis. In both cases, the ciliary defect associated with this syndrome is the absence of inner dynein arms.

Study of Mucociliary Transport and Nasal Ciliary Ultrastructure in Patients With Kartagener's Syndrome

Kartagener's syndrome (KS) is a clinical variant of primary ciliary dyskinesia involving situs inversus associated with chronic airway infections. The ciliary defect associated with this syndrome is the absence of dynein arms. The aim of this study was to evaluate mucociliary transport and ciliary ultrastructure in 14 patients with KS. We studied nasal mucociliary transport using a radioisotopic technique and ciliary ultrastructure in 14 patients with KS. Thirteen patients had mucociliary stasis and 1 had severely slowed transport (1.3 mm/min). Four patients (29%) had cilia with normal dynein arms, 2 patients (14%) had short inner dynein arms, and 8 patients (57.1%) had total absence of inner and outer dynein arms. We conclude that the typical clinical presentation, together with altered mucociliary transport as identified by an isotopic technique, is diagnostic of KS, even when the ciliary ultrastructure is normal. KS is clinically homogenous and morphologically heterogenous.

Absence of Nexin Links as a Possible Causeof Primary Ciliary Dyskinesia

Transmission electron microscopy of nasal cilia was performed in three patients, two of them siblings, with repeated respiratory infections. Number of microtubuli and dynein arms were within normal limits and they had an ordered arrangement except for a disarray of the microtubuli in some areas of the biopsies from two of the patients. In the normal areas radial spokes and sheaths were easily found but nexin links could not be discerned in any of the patients. The orientation of the cilia was partly random. As all patients repeatedly and constantly had very low nasal NO (range 9-15 ppb; normal findings for persons <10 years old are > 50 ppb), the diagnoses were very likely primary ciliary dyskinesia (PCD). Absence of nexin links may be an ultrastructural variant of PCD. Deficiency of these structures might be the cause of the microtubular disarray observed in some areas of the biopsies.

Long-term follow-up of the clinical relevance of short outer dynein arms in human nasal cilia.

Clinical significance of short outer dynein arms was examined in a long-term follow-up study of 76 patients with various respiratory symptoms. Clinical evaluations, nasal mucociliary transport rate (NMTR) measurement and transmission electron microscopy were performed. Follow-up examinations took place 5-11 years later. In the initial examination four patients and on follow-up seven patients were found to have short outer dynein arms in their nasal mucosal biopsies. Short dynein arms were associated with a slow NMTR, poorly coordinated ciliary beat direction, and clinical symptoms of perennial rhinitis and recurrent sinusitis. Short dynein arms were found to be a significant histologic finding and probably represent a variant of primary ciliary dyskinesia. In some cases short outer dynein arms may be a reversible finding with improving clinical symptoms. It is obvious that at least part of dynein defects are acquired.

Ciliary disorientation alone as a cause of primary ciliary dyskinesia syndrome.

Ciliary disorientation has been proposed as a variant of primary ciliary dyskinesia (PCD); cilia have normal ultrastructure and normal or near normal ciliary beat frequency (CBF) but lack efficacy because their beat direction is disorientated. We have identified 11 patients, including two siblings, with the clinical features of PCD, who satisfy these criteria. A chest radiograph, pulmonary function tests, nasal mucociliary clearance (NMCC), CBF, ciliary ultrastructure, and orientation were assessed in each subject. One patient had biopsies taken from the nose and both main bronchi. Eight patients had a computed tomography scan (CT) of the thorax; the clinical features were compatible with PCD. Cilia ultrastructure was normal and NMCC was absent in all cases. Mean CBF was normal (11.6-14.9 Hz) in five cases and slow in six (range 8.4-9.7 Hz). Ciliary beat pattern was stiff in seven cases, six of which had slow CBF. The cilia were disorientated when measured by both the central pair (range, 21.8 degrees - 26.4 degrees) and basal feet (range, 20.6 degrees - 28.9 degrees) compared with 16 normal controls (range, 11.0 degrees - 15.5 degrees and 12.3 degrees - 17.6 degrees, respectively). Two siblings had the clinical features of PCD and ciliary disorientation alone on repeated biopsies taken 10 yr apart. Orientation of cilia from the nose and bronchus was similar. Two cases had unchanged ciliary disorientation after 3 mo of treatment with antibiotics and topical corticosteroids. We concluded that ciliary disorientation alone can lead to the clinical syndrome of PCD.