DNAI1 mutations explain only 2% of primary ciliary dykinesia

Ependymal Cilia: Physiology and Role in Hydrocephalus

Cerebrospinal fluid (CSF), a colorless liquid that generally circulates from the lateral ventricles to the third and fourth ventricles, provides essential nutrients for brain homeostasis and growth factors during development. As evidenced by an increasing corpus of research, CSF serves a range of important functions. While it is considered that decreased CSF flow is associated to the development of hydrocephalus, it has recently been postulated that motile cilia, which line the apical surfaces of ependymal cells (ECs), play a role in stimulating CSF circulation by cilia beating. Ependymal cilia protrude from ECs, and their synchronous pulsing transports CSF from the lateral ventricle to the third and fourth ventricles, and then to the subarachnoid cavity for absorption. As a result, we postulated that malfunctioning ependymal cilia could disrupt normal CSF flow, raising the risk of hydrocephalus. This review aims to demonstrate the physiological functions of ependymal cilia, as well as how cilia immobility or disorientation causes problems. We also conclude conceivable ways of treatment of hydrocephalus currently for clinical application and provide theoretical support for regimen improvements by investigating the relationship between ependymal cilia and hydrocephalus development.

The global prevalence and ethnic heterogeneity of primary ciliary dyskinesia gene variants: a genetic database analysis

BACKGROUND

Primary ciliary dyskinesia (PCD) is a motile ciliopathy characterised by otosinopulmonary infections. Inheritance is commonly autosomal recessive, with extensive locus and allelic heterogeneity. The prevalence is uncertain. Most genetic studies have been done in North America or Europe. The aim of the study was to estimate the worldwide prevalence and ethnic heterogeneity of PCD.

METHODS

We calculated the allele frequency of disease-causing variants in 29 PCD genes associated with autosomal recessive inheritance in 182 681 unique individuals to estimate the global prevalence of PCD in seven ethnicities (African or African American, Latino, Ashkenazi Jewish, Finnish, non-Finnish European, east Asian, and south Asian). We began by aggregating variants that had been interpreted by Invitae, San Francisco, CA, USA, a genetics laboratory with PCD expertise. We then determined the allele frequency of each variant (pathogenic, likely pathogenic, or variant of uncertain significance [VUS]) in the Genome Aggregation Database (gnomAD), a publicly available next-generation sequencing database that aggregates exome and genome sequencing information from a wide variety of large-scale projects and stratifies allele counts by ethnicity. Using the Hardy-Weinberg equilibrium equation, we were able to calculate a lower-end prevalence of PCD for each ethnicity by including only pathogenic and likely pathogenic variants; and upper-end prevalence by also including VUS. This approach was similar to previous work on Li-Fraumeni (TP53 variants) prevalence. We were not diagnosing PCD, but rather estimating prevalence based on known variants.

FINDINGS

The overall minimum global prevalence of PCD is calculated to be at least one in 7554 individuals, although this is likely to be an underestimate because some variants currently classified as VUS might be disease-causing and some pathogenic variants might not be detected by our methods. In the overall cohort, Invitae data could be included for variants without gnomAD data for a primary ethnicity. When using only gnomAD allele frequencies to calculate prevalence in individual ethnicities, the estimated prevalence of PCD was lower in each ethnicity compared with the overall cohort. This is because the overall cohort includes additional data from the Invitae database such as copy number variants and other variants not present in gnomAD. With gnomAD we found the expected PCD frequency to be higher in individuals of African ancestry than in most other populations (excluding VUS: 1 in 9906 in African or African American vs 1 in 10 388 in non-Finnish European vs 1 in 14 606 in east Asian vs 1 in 16 309 in Latino; including VUS: 1 in 106 in African or African American vs 1 in 178 in non-Finnish European vs 1 in 196 in Latino vs 1 in 188 in east Asian). In addition, we found that the top 5 genes most commonly implicated in PCD differed across ethnic ancestries and contrasted commonly published findings.

INTERPRETATION

PCD appears to be more common than has been recognised, particularly in individuals of African ancestry. We identified gene distributions that differ from those in previous European and North American studies. These results could have an international impact on case identification. Our analytic approach can be expanded as more PCD loci are identified, and could be adapted to study the prevalence of other inherited diseases.

FUNDING

None.

Whole-exome sequencing reveals a combination of extremely rare single-nucleotide polymorphism of DNAH9 and RSPH1 genes in a Japanese fetus with situs viscerum inversus

Randomization of left-right body asymmetry, situs viscerum inversus (heterotaxy), is commonly associated with primary ciliary dyskinesia (PCD) resulting from an abnormal ciliary structure, with approximately 50% of PCD patients exhibiting organ laterality defects. I herein report an intrauterine fetal death case, in which an autopsy revealed two lobes of the bilateral lungs as well as heterotaxy of abdominal organs (right-sided spleen and inversion of the alimentary and biliary organs). Whole-exome sequencing (WES) identified a heterozygous single-nucleotide change (c.12775T>C) in exon 68 of the DNAH9 gene, which is a rare single-nucleotide polymorphism (SNP) of rs746081639 and results in the amino acid change of p.C4259R. WES also identified a rare SNP of rs763089682 (c.121G>A) in the RSPH1 gene that causes a heterozygous amino acid alteration of p.G41R. The frequencies of both SNPs, C in rs746081639 and A in rs763089682, are 0.00000824, and a polyphen-2 analysis predicted these amino acid changes to be probably damaging, with a score of 1.000. The combination of extremely rare SNPs in DNAH9 and RSPH1 genes might have been the possible mechanism underlying the development of the laterality defect in the present case.

Novel gene variants in patients with platelet-based bleeding using combined exome sequencing and RNAseq murine expression data

Essentials Identifying genetic variants in platelet disorders is challenging due to its heterogenous nature. We combine WES, RNAseq, and python-based bioinformatics to identify novel gene variants. We find novel candidates in patient data by cross-referencing against a murine RNAseq model of thrombopoiesis. This innovative combined bioinformatic approach provides novel data for future research in the field. ABSTRACT: Background The UK Genotyping and Phenotyping of Platelets study has recruited and analyzed 129 patients with suspected heritable bleeding. Previously, 55 individuals had a definitive genetic diagnosis based on whole exome sequencing (WES) and platelet morphological and functional testing. A significant challenge in this field is defining filtering criteria to identify the most likely candidate mutations for diagnosis and further study. Objective Identify candidate gene mutations for the remaining 74 patients with platelet-based bleeding with unknown genetic cause, forming the basis of future re-recruitment and further functional testing and assessment. Methods Using python-based data frame indexing, we first identify and filter all novel and rare variants using a panel of 116 genes known to cause bleeding across the full cohort of WES data. This identified new variants not previously reported in this cohort. We then index the remaining patients, with rare or novel variants in known bleeding genes against a murine RNA sequencing dataset that models proplatelet-forming megakaryocytes. Results Filtering against known genes identified candidate variants in 59 individuals, including novel variants in several known genes. In the remaining cohort of "unknown" patients, indexing against differentially expressed genes revealed candidate gene variants in several novel unreported genes, focusing on 14 patients with a severe clinical presentation. Conclusions We identified candidate mutations in a cohort of patients with no previous genetic diagnosis. This work involves innovative coupling of RNA sequencing and WES to identify candidate variants forming the basis of future study in a significant number of undiagnosed patients.

EBT: a statistic test identifying moderate size of significant features with balanced power and precision for genome-wide rate comparisons

Motivation

In genome-wide rate comparison studies, there is a big challenge for effective identification of an appropriate number of significant features objectively, since traditional statistical comparisons without multi-testing correction can generate a large number of false positives while multi-testing correction tremendously decreases the statistic power.

Results

In this study, we proposed a new exact test based on the translation of rate comparison to two binomial distributions. With modeling and real datasets, the exact binomial test (EBT) showed an advantage in balancing the statistical precision and power, by providing an appropriate size of significant features for further studies. Both correlation analysis and bootstrapping tests demonstrated that EBT is as robust as the typical rate-comparison methods, e.g. χ 2 test, Fisher's exact test and Binomial test. Performance comparison among machine learning models with features identified by different statistical tests further demonstrated the advantage of EBT. The new test was also applied to analyze the genome-wide somatic gene mutation rate difference between lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), two main lung cancer subtypes and a list of new markers were identified that could be lineage-specifically associated with carcinogenesis of LUAD and LUSC, respectively. Interestingly, three cilia genes were found selectively with high mutation rates in LUSC, possibly implying the importance of cilia dysfunction in the carcinogenesis.

Availability and implementation

An R package implementing EBT could be downloaded from the website freely: http://www.szu-bioinf.org/EBT .

Contact

wangyj@szu.edu.cn.

Supplementary information

Supplementary data are available at Bioinformatics online.

An effective combination of sanger and next generation sequencing in diagnostics of primary ciliary dyskinesia

BACKGROUND

Primary ciliary dyskinesia (PCD) is a multigenic autosomal recessive condition affecting respiratory tract and other organs where ciliary motility is required. The extent of its genetic heterogeneity is remarkable. The aim of the study was to develop a cost-effective pipeline for genetic diagnostics using a combination of Sanger and next generation sequencing (NGS).

MATERIALS AND METHODS

Data and samples of 33 families with 38 affected subjects with PCD diagnosed in childhood were collected over the territory of the Czech Republic. A panel of 18 PCD causative or candidate genes was implemented into an Illumina TruSeq Custom Amplicon NGS assay, and three ancestral mutations in SPAG1 were screened by conventional Sanger sequencing, which was also used for the confirmation of the NGS results and for the analysis of familial segregation.

RESULTS

The causative gene was DNAH5 in 11/33 (33%) probands, SPAG1 in 8/33 (24%), and DNAI1, CCDC40, LRRC6 in one family each. If the high proportion of subjects with bi-allelic ancestral mutations in SPAG1 is corroborated in other Caucasian populations, a simple Sanger sequencing test for these three mutations may serve as an effective pre-screening step, being followed by an NGS panel for other, much larger, PCD genes.

CONCLUSIONS

We present a combination of Sanger sequencing with an NGS panel for known and candidate PCD genes, implemented in a moderate-size national collection of patients. This strategy has proven to be cost-effective, rapid and reliable, and was able to detect the causative gene in two thirds of our PCD patients.

Diagnostic Methods in Primary Ciliary Dyskinesia

Diagnosing primary ciliary dyskinesia is difficult. With no reference standard, a combination of tests is needed; most tests require expensive equipment and specialist scientists. We review the advances in diagnostic testing over the past hundred years, with emphasis on recent advances. We particularly focus on use of high-speed video analysis, transmission electron microscopy, nasal nitric oxide and genetic testing. We discuss the international efforts that are in place to advance the evidence base for diagnostic tests.

Unique among ciliopathies: primary ciliary dyskinesia, a motile cilia disorder

Primary ciliary dyskinesia (PCD) is a ciliopathy, but represents the sole entity from this class of disorders that results from the dysfunction of motile cilia. Characterized by respiratory problems appearing in childhood, infertility, and situs defects in ~50% of individuals, PCD has an estimated prevalence of approximately 1 in 10,000 live births. The diagnosis of PCD can be prolonged due to a lack of disease awareness, coupled with the fact that symptoms can be confused with other more common genetic disorders, such as cystic fibrosis, or environmental insults that result in frequent respiratory infections. A primarily autosomal recessive disorder, PCD is genetically heterogeneous with >30 causal genes identified, posing significant challenges to genetic diagnosis. Here, we provide an overview of PCD as a disorder underscored by impaired ciliary motility; we discuss the recent advances towards uncovering the genetic basis of PCD; we discuss the molecular knowledge gained from PCD gene discovery, which has improved our understanding of motile ciliary assembly; and we speculate on how accelerated diagnosis, together with detailed phenotypic data, will shape the genetic and functional architecture of this disorder.

Genetic basis of human left-right asymmetry disorders

Humans and other vertebrates exhibit left-right (LR) asymmetric arrangement of the internal organs, and failure to establish normal LR asymmetry leads to internal laterality disorders, including situs inversus and heterotaxy. Situs inversus is complete mirror-imaged arrangement of the internal organs along LR axis, whereas heterotaxy is abnormal arrangement of the internal thoraco-abdominal organs across LR axis of the body, most of which are associated with complex cardiovascular malformations. Both disorders are genetically heterogeneous with reduced penetrance, presumably because of monogenic, polygenic or multifactorial causes. Research in genetics of LR asymmetry disorders has been extremely prolific over the past 17 years, and a series of loci and disease genes involved in situs inversus and heterotaxy have been described. The review highlights the classification, chromosomal abnormalities, pathogenic genes and the possible mechanism of human LR asymmetry disorders.

The role of molecular genetic analysis in the diagnosis of primary ciliary dyskinesia

RATIONALE

Primary ciliary dyskinesia (PCD) is an autosomal recessive genetic disorder of motile cilia. The diagnosis of PCD has previously relied on ciliary analysis with transmission electron microscopy or video microscopy. However, patients with PCD may have normal ultrastructural appearance, and ciliary analysis has limited accessibility. Alternatively, PCD can be diagnosed by demonstrating biallelic mutations in known PCD genes. Genetic testing is emerging as a diagnostic tool to complement ciliary analysis where interpretation and access may delay diagnosis.

OBJECTIVES

To determine the diagnostic yield of genetic testing of patients with a confirmed or suspected diagnosis of PCD in a multiethnic urban center.

METHODS

Twenty-eight individuals with confirmed PCD on transmission electron microscopy of ciliary ultrastructure and 24 individuals with a probable diagnosis of PCD based on a classical PCD phenotype and low nasal nitric oxide had molecular analysis of 12 genes associated with PCD.

RESULTS

Of 49 subjects who underwent ciliary biopsy, 28 (57%) were diagnosed with PCD through an ultrastructural defect. Of the 52 individuals who underwent molecular genetic analysis, 22 (42%) individuals had two mutations in known PCD genes. Twenty-four previously unreported mutations in known PCD genes were observed. Combining both diagnostic modalities of biopsy and molecular genetics, the diagnostic yield increased to 69% compared with 57% based on biopsy alone.

CONCLUSIONS

The diagnosis of PCD is challenging and has traditionally relied on ciliary biopsy, which is unreliable as the sole criterion for a definitive diagnosis. Molecular genetic analysis can be used as a complementary test to increase the diagnostic yield.

Recent advances in primary ciliary dyskinesia genetics

Primary ciliary dyskinesia (PCD) is a rare genetically heterogeneous disorder caused by the abnormal structure and/or function of motile cilia. The PCD diagnosis is challenging and requires a well-described clinical phenotype combined with the identification of abnormalities in ciliary ultrastructure and/or beating pattern as well as the recognition of genetic cause of the disease. Regarding the pace of identification of PCD-related genes, a rapid acceleration during the last 2-3 years is notable. This is the result of new technologies, such as whole-exome sequencing, that have been recently applied in genetic research. To date, PCD-causative mutations in 29 genes are known and the number of causative genes is bound to rise. Even though the genetic causes of approximately one-third of PCD cases still remain to be found, the current knowledge can already be used to create new, accurate genetic tests for PCD that can accelerate the correct diagnosis and reduce the proportion of unexplained cases. This review aims to present the latest data on the relations between ciliary structure aberrations and their genetic basis.

Recent advances in primary ciliary dyskinesia genetics

Primary ciliary dyskinesia (PCD) is a rare genetically heterogeneous disorder caused by the abnormal structure and/or function of motile cilia. The PCD diagnosis is challenging and requires a well-described clinical phenotype combined with the identification of abnormalities in ciliary ultrastructure and/or beating pattern as well as the recognition of genetic cause of the disease. Regarding the pace of identification of PCD-related genes, a rapid acceleration during the last 2–3 years is notable. This is the result of new technologies, such as whole-exome sequencing, that have been recently applied in genetic research. To date, PCD-causative mutations in 29 genes are known and the number of causative genes is bound to rise. Even though the genetic causes of approximately one-third of PCD cases still remain to be found, the current knowledge can already be used to create new, accurate genetic tests for PCD that can accelerate the correct diagnosis and reduce the proportion of unexplained cases. This review aims to present the latest data on the relations between ciliary structure aberrations and their genetic basis.

A novel mutation of the axonemal dynein heavy chain gene 5 (DNAH5) in a Japanese neonate with asplenia syndrome

Asplenia syndrome (Ivemark syndrome) is a complex disorder composed of asplenia, malpositioning of the visceral organs and congenital heart defects. To elucidate the underlying molecular mechanism of asplenia syndrome, we herein analyzed the fatal case of a male neonate who exhibited three lobes of the left lung, asplenia and complex heart anomalies and died 6 hours after delivery. A whole-exome sequence (WES) analysis followed by Sanger sequence identified a heterozygous single nucleotide change (c.7829A>G) in exon 47 of the axonemal dynein heavy chain gene 5 (DNAH5), which results in the missense mutation of p.Glu2610Gly. This mutation was found only in the neonate, but not in his parents, implying de novo mutation of DNAH5 that codes dynein heavy chain, a component of outer dynein arm. The WES analysis also identified a heterozygous single nucleotide substitution (c.3697C>T) in the axonemal dynein heavy chain gene 7 (DNAH7), resulting in p.Arg1233Cys, and a rare SNP (c.2029G>A, p.Gly677Ser) of the axonemal dynein intermediate chain gene 1 (DNAI1) in the patient and his mother, but not in his father. The mutation of p.Glu2610Gly in DNAH5 is novel and we here present a first Japanese case of asplenia syndrome who exhibited a DNAH5 mutation.

Primary ciliary dyskinesia: clinical criteria indicating ultrastructural studies

INTRODUCTION

Primary ciliary dyskinesia (PCD) is a congenital disease characterized by impaired ciliary function, which involves a wide range of symptoms that are mainly respiratory. Recent articles that base diagnosis on ciliary ultrastructural studies have estimated its prevalence to be 1/10,000 newborns, which is higher than previously thought. Our objective is to define criteria for clinical suspicion of DCP that would indicate ultrastructural studies, while optimizing these and providing early diagnoses.

METHODS

Ours is a descriptive, retrospective review of patients diagnosed with DCP in the Pediatric Pulmonology Unit at our hospital, from 1994 to 2010. The inclusion of cases was based on clinical suspicion criteria. Diagnosis was confirmed by characteristic ultrastructural changes observed in the electron microscopic study of the cilia.

RESULTS

Sixty-three samples were analyzed, and 34 cases of DCP and one case of acilia were confirmed. Mean age at diagnosis was 3.6 (range: 1 month to 19 years of age). The most frequent initial symptom was prolonged neonatal tachypnea in the newborns (20%) and lower respiratory tract episodes in the school-aged patients: recurrent pneumonia (46%), difficult-to-control asthma (26%), bronchiectasis (8.6%) and massive atelectasis (2.9%). Associated symptoms were present in 46% of the cases.

CONCLUSION

Our publication proposes the implementation of several clinical criteria depending on the age of presentation that would indicate the active search for alterations in the ciliary epithelium at reference centers.

Effectiveness of sequencing selected exons of DNAH5 and DNAI1 in diagnosis of primary ciliary dyskinesia

INTRODUCTION

Primary ciliary dyskinesia (PCD) is a rare genetically heterogenous condition. Mutations in DNAH5 or DNAI1 genes can be found in about a third of the patients with PCD. Increased occurrence of mutations was described in several exons of these long genes. The objective of the study was to test the sensitivity of sequencing of selected 13 exons (as compared to costly sequencing of all 100 exons of the two genes), and to determine the prevalence of the DNAH5 or DNAI1 mutations in the Czech PCD database.

METHODS

The Czech national PCD database has identified 31 pediatric patients, diagnosed based on clinical findings and tests on the ciliated epithelium. Twenty-seven patients from 24 families agreed on genetic testing. In the first step, direct sequencing of selected 13 exons (9 of DNAH5 and 4 of DNAI1) was performed, and then we compared its effectiveness in detecting at least one mutation with results of sequencing all 100 exons of the two genes.

RESULTS

The sequencing of all exons identified compound heterozygosity for PCD mutations in nine patients from eight families (DNAH5 in eight and DNAI1 in one patient), and heterozygozity for a DNAH5 mutation of uncertain functional significance in one additional patient. The first step of selected exon sequencing detected a mutation in five out of these eight families, its actual sensitivity being 62.5%, with a high predictive value. The phenotypic and clinical characteristics of all the paediatric patients with PCD are shown.

CONCLUSIONS

Selected exon sequencing detects at least one mutated allele in over a half of our patients who have PCD due to DNAH5 or DNAI1 mutations. To lower the costs of the genetic testing, targeted step-wise genetic testing may be a reasonable approach to detect mutations in PCD patients, especially if their phenotype is taken into account.

Mutations of DNAH11 in patients with primary ciliary dyskinesia with normal ciliary ultrastructure

RATIONALE

Primary ciliary dyskinesia (PCD) is an autosomal recessive, genetically heterogeneous disorder characterised by oto-sino-pulmonary disease and situs abnormalities (Kartagener syndrome) due to abnormal structure and/or function of cilia. Most patients currently recognised to have PCD have ultrastructural defects of cilia; however, some patients have clinical manifestations of PCD and low levels of nasal nitric oxide, but normal ultrastructure, including a few patients with biallelic mutations in dynein axonemal heavy chain 11 (DNAH11).

OBJECTIVES

To test further for mutant DNAH11 as a cause of PCD, DNAH11 was sequenced in patients with a PCD clinical phenotype, but no known genetic aetiology.

METHODS

82 exons and intron/exon junctions in DNAH11 were sequenced in 163 unrelated patients with a clinical phenotype of PCD, including those with normal ciliary ultrastructure (n=58), defects in outer and/or inner dynein arms (n=76), radial spoke/central pair defects (n=6), and 23 without definitive ultrastructural results, but who had situs inversus (n=17), or bronchiectasis and/or low nasal nitric oxide (n=6). Additionally, DNAH11 was sequenced in 13 subjects with isolated situs abnormalities to see if mutant DNAH11 could cause situs defects without respiratory disease.

RESULTS

Of the 58 unrelated patients with PCD with normal ultrastructure, 13 (22%) had two (biallelic) mutations in DNAH11; and two patients without ultrastructural analysis had biallelic mutations. All mutations were novel and private. None of the patients with dynein arm or radial spoke/central pair defects, or isolated situs abnormalities, had mutations in DNAH11. Of the 35 identified mutant alleles, 24 (69%) were nonsense, insertion/deletion or loss-of-function splice-site mutations.

CONCLUSIONS

Mutations in DNAH11 are a common cause of PCD in patients without ciliary ultrastructural defects; thus, genetic analysis can be used to ascertain the diagnosis of PCD in this challenging group of patients.

Mutations in radial spoke head genes and ultrastructural cilia defects in East-European cohort of primary ciliary dyskinesia patients

Primary ciliary dyskinesia (PCD) is a rare (1/20,000), multisystem disease with a complex phenotype caused by the impaired motility of cilia/flagella, usually related to ultrastructural defects of these organelles. Mutations in genes encoding radial spoke head (RSPH) proteins, elements of the ciliary ultrastructure, have been recently described. However, the relative involvement of RSPH genes in PCD pathogenesis remained unknown, due to a small number of PCD families examined for mutations in these genes. The purpose of this study was to estimate the involvement of RSPH4A and RSPH9 in PCD pathogenesis among East Europeans (West Slavs), and to shed more light on ultrastructural ciliary defects caused by mutations in these genes. The coding sequences of RSPH4A and RSPH9 were screened in PCD patients from 184 families, using single strand conformational polymorphism analysis and sequencing. Two previously described (Q109X; R490X) and two new RSPH4A mutations (W356X; IVS3_2–5del), in/around exons 1 and 3, were identified; no mutations were found in RSPH9. We estimate that mutations in RSPH4A, but not in RSPH9, are responsible for 2–3% of cases in the East European PCD population (4% in PCD families without situs inversus; 11% in families preselected for microtubular defects). Analysis of the SNP-haplotype background provided insight into the ancestry of repetitively found mutations (Q109X; R490X; IVS3_2–5del), but further studies involving other PCD cohorts are required to elucidate whether these mutations are specific for Slavic people or spread among other European populations. Ultrastructural defects associated with the mutations were analyzed in the transmission electron microscope images; almost half of the ciliary cross-sections examined in patients with RSPH4A mutations had the microtubule transposition phenotype (9+0 and 8+1 pattern). While microtubule transposition was a prevalent ultrastructural defect in cilia from patients with RSPH4A mutations, similar defects were also observed in PCD patients with mutations in other genes.

Ciliary motility: the components and cytoplasmic preassembly mechanisms of the axonemal dyneins

Motile cilia and flagella are organelles, which function in cell motility and in the transport of fluids over the surface of cells. Motility defects often result in a rare human disease, primary ciliary dyskinesia (PCD). Cell motility depends on axonemal dynein, a molecular motor that drives the beating of cilia and flagella. The dyneins are composed of multiple subunits, which are thought to be preassembled in the cytoplasm before they are transported into cilia and flagella. Axonemal dyneins have been extensively studied in Chlamydomonas. In addition, analyses of human PCDs over the past decade, together with studies in other model animals, have identified the conserved components required for dynein assembly. Recently also, the first cytoplasmic component of dynein assembly, kintoun (ktu), was elucidated through the analysis of a medaka mutant in combination with human genetics and cell biology and biochemical studies of Chlamydomonas. The components of dynein and the proteins involved in its cytoplasmic assembly process are discussed.

Normal live birth after testicular sperm extraction and intracytoplasmic sperm injection in variant primary ciliary dyskinesia with completely immotile sperm and structurally abnormal sperm tails

OBJECTIVE

To report on the investigation and fertility management of variant primary ciliary dyskinesia (PCD).

DESIGN

Case report.

SETTING

University-affiliated assisted reproductive technologies practice.

PATIENT(S)

A 40 year-old man presenting with 12 months' primary infertility, complete sperm immotility, severe morphologic defects, and moderate sinopulmonary disease.

INTERVENTION(S)

Electron microscopy (EM) of sperm, nasal cilial function studies, open testis biopsy, and sperm extraction for intracytoplasmic sperm injection (ICSI).

MAIN OUTCOME MEASURE(S)

Outcome of ICSI treatment using immotile testicular sperm.

RESULT(S)

EM revealed abnormal connecting pieces, shortened midpieces with attenuated mitochondrial sheaths, poorly developed annulus, abnormal outer dense fibers, and axonemes missing the two central mircotubules. Nasal ciliary beat frequency was subnormal and dyssynchronous. Immotile testicular sperm were selected for ICSI based on physical characteristics and fertilized 12 of 18 eggs. A single day-5 blastocyst achieved a normal pregnancy and delivery of a healthy 3,840-g girl at 38 weeks' gestation.

CONCLUSION(S)

Nonclassic PCD may present with structurally abnormal completely immotile sperm, with seemingly little prospect of fertility, and moderate respiratory dysfunction supporting the presence of an underlying ciliopathy. Despite testicular sperm also being immotile and showing profound structural defects that would seem to preclude fertilization, more morphologically normal sperm are capable of establishing a normal pregnancy.

Primary ciliary dyskinesia caused by homozygous mutation in DNAL1, encoding dynein light chain 1

In primary ciliary dyskinesia (PCD), genetic defects affecting motility of cilia and flagella cause chronic destructive airway disease, randomization of left-right body asymmetry, and, frequently, male infertility. The most frequent defects involve outer and inner dynein arms (ODAs and IDAs) that are large multiprotein complexes responsible for cilia-beat generation and regulation, respectively. Although it has long been suspected that mutations in DNAL1 encoding the ODA light chain1 might cause PCD such mutations were not found. We demonstrate here that a homozygous point mutation in this gene is associated with PCD with absent or markedly shortened ODA. The mutation (NM_031427.3: c.449A>G; p.Asn150Ser) changes the Asn at position150, which is critical for the proper tight turn between the β strand and the α helix of the leucine-rich repeat in the hydrophobic face that connects to the dynein heavy chain. The mutation reduces the stability of the axonemal dynein light chain 1 and damages its interactions with dynein heavy chain and with tubulin. This study adds another important component to understanding the types of mutations that cause PCD and provides clinical information regarding a specific mutation in a gene not yet known to be associated with PCD.

Population specificity of the DNAI1 gene mutation spectrum in primary ciliary dyskinesia (PCD)

Background

Mutations in the DNAI1 gene, encoding a component of outer dynein arms of the ciliary apparatus, are the second most important genetic cause of primary ciliary dyskinesia (PCD), the genetically heterogeneous recessive disorder with the prevalence of ~1/20,000. The estimates of the DNAI1 involvement in PCD pathogenesis differ among the reported studies, ranging from 4% to 10%.

Methods

The coding sequence of DNAI1 was screened (SSCP analysis and direct sequencing) in a group of PCD patients (157 families, 185 affected individuals), the first ever studied large cohort of PCD patients of Slavic origin (mostly Polish); multiplex ligation-dependent probe amplification (MLPA) analysis was performed in a subset of ~80 families.

Results

Three previously reported mutations (IVS1+2-3insT, L513P and A538T) and two novel missense substitutions (C388Y and G515S) were identified in 12 families (i.e. ~8% of non-related Polish PCD patients). The structure of background SNP haplotypes indicated common origin of each of the two most frequent mutations, IVS1+2-3insT and A538T. MLPA analysis did not reveal any significant differences between patients and control samples. The Polish cohort was compared with all the previously studied PCD groups (a total of 487 families): IVS1+2-3insT remained the most prevalent pathogenetic change in DNAI1 (54% of the mutations identified worldwide), and the increased global prevalence of A538T (14%) was due to the contribution of the Polish cohort.

Conclusions

The worldwide involvement of DNAI1 mutations in PCD pathogenesis in families not preselected for ODA defects ranges from 7 to 10%; this global estimate as well as the mutation profile differs in specific populations. Analysis of the background SNP haplotypes suggests that the increased frequency of chromosomes carrying A538T mutations in Polish patients may reflects local (Polish or Slavic) founder effect. Results of the MLPA analysis indicate that no large exonic deletions are involved in PCD pathogenesis.

In vitro culturing of ciliary respiratory cells--a model for studies of genetic diseases

Primary ciliary dyskinesia (PCD) is a rare genetic disorder caused by the impaired functioning of ciliated cells. Its diagnosis is based on the analysis of the structure and functioning of cilia present in the respiratory epithelium (RE) of the patient. Abnormalities of cilia caused by hereditary mutations closely resemble and often overlap with defects induced by the environmental factors. As a result, proper diagnosis of PCD is difficult and may require repeated sampling of patients' tissue, which is not always possible. The culturing of differentiated cells and tissues derived from the human RE seems to be the best way to diagnose PCD, to study genotype-phenotype relations of genes involved in ciliary dysfunction, as well as other aspects related to the functioning of the RE. In this review, different methods of culturing differentiated cells and tissues derived from the human RE, along with their potential and limitations, are summarized. Several considerations with respect to the factors influencing the process of in vitro differentiation (cell-to-cell interactions, medium composition, cell-support substrate) are also discussed.

The molecular basis of human retinal and vitreoretinal diseases

During the last two to three decades, a large body of work has revealed the molecular basis of many human disorders, including retinal and vitreoretinal degenerations and dysfunctions. Although belonging to the group of orphan diseases, they affect probably more than two million people worldwide. Most excitingly, treatment of a particular form of congenital retinal degeneration is now possible. A major advantage for treatment is the unique structure and accessibility of the eye and its different components, including the vitreous and retina. Knowledge of the many different eye diseases affecting retinal structure and function (night and colour blindness, retinitis pigmentosa, cone and cone rod dystrophies, photoreceptor dysfunctions, as well as vitreoretinal traits) is critical for future therapeutic development. We have attempted to present a comprehensive picture of these disorders, including biological, clinical, genetic and molecular information. The structural organization of the review leads the reader through non-syndromic and syndromic forms of (i) rod dominated diseases, (ii) cone dominated diseases, (iii) generalized retinal degenerations and (iv) vitreoretinal disorders, caused by mutations in more than 165 genes. Clinical variability and genetic heterogeneity have an important impact on genetic testing and counselling of affected families. As phenotypes do not always correlate with the respective genotypes, it is of utmost importance that clinicians, geneticists, counsellors, diagnostic laboratories and basic researchers understand the relationships between phenotypic manifestations and specific genes, as well as mutations and pathophysiologic mechanisms. We discuss future perspectives.

Founder mutation(s) in the RSPH9 gene leading to primary ciliary dyskinesia in two inbred Bedouin families

A rare mutation in the RSPH9 gene leading to primary ciliary dyskinesia was previously identified in two Bedouin families, one from Israel and one from the United Arab Emirates (UAE). Herein we analyse mutation segregation in the Israeli family, present the clinical disease spectrum, and estimate mutation age in the two families. Mutation segregation was studied by restriction fragment length analysis. Mutation ages were estimated using a model of the decrease in the length of ancestral haplotypes. The mutations in each of the two families had a common ancestor less than 95 and less than 17 generations in the past. If the mutations in the two families are descended from a common ancestor, that mutation would have to have arisen at least 150 generations ago. If the Bedouin population has been roughly constant in size for at least 6000 years, it is possible that the mutations in the two families are identical by descent. If there were substantial fluctuations in the size of the Bedouin population, it is more likely that there were two independent mutations. Based on the available data, the population genetic analysis does not strongly favour one conclusion over the other.

Non-cystic fibrosis bronchiectasis: review and recent advances

Bronchiectasis is an abnormal dilatation of bronchi and bronchioles associated with repeated cycles of airway infection and inflammation. This review will focus on non-cystic fibrosis bronchiectasis in children, with regard to etiology, diagnosis, treatment options, and recent advances.

Clinical and genetic aspects of primary ciliary dyskinesia/Kartagener syndrome

Primary ciliary dyskinesia is a genetically heterogeneous disorder of motile cilia. Most of the disease-causing mutations identified to date involve the heavy (dynein axonemal heavy chain 5) or intermediate(dynein axonemal intermediate chain 1) chain dynein genes in ciliary outer dynein arms, although a few mutations have been noted in other genes. Clinical molecular genetic testing for primary ciliary dyskinesia is available for the most common mutations. The respiratory manifestations of primary ciliary dyskinesia (chronic bronchitis leading to bronchiectasis, chronic rhino-sinusitis, and chronic otitis media)reflect impaired mucociliary clearance owing to defective axonemal structure. Ciliary ultrastructural analysis in most patients (>80%) reveals defective dynein arms, although defects in other axonemal components have also been observed. Approximately 50% of patients with primary ciliary dyskinesia have laterality defects (including situs inversus totalis and, less commonly, heterotaxy, and congenital heart disease),reflecting dysfunction of embryological nodal cilia. Male infertility is common and reflects defects in sperm tail axonemes. Most patients with primary ciliary dyskinesia have a history of neonatal respiratory distress, suggesting that motile cilia play a role in fluid clearance during the transition from a fetal to neonatal lung. Ciliopathies involving sensory cilia, including autosomal dominant or recessive polycystic kidney disease, Bardet-Biedl syndrome, and Alstrom syndrome, may have chronic respiratory symptoms and even bronchiectasis suggesting clinical overlap with primary ciliary dyskinesia.

Primary ciliary dyskinesia: improving the diagnostic approach

PURPOSE OF REVIEW

The diagnosis of primary ciliary dyskinesia (PCD) has relied on analysis of ciliary motility and ultrastructure; however, these tests are not readily available and have not been standardized. Consequently, the diagnosis of PCD may be delayed or missed or made incorrectly. This review outlines the potential utility of new diagnostic tests, including measurement of nasal nitric oxide production and systematic analysis for mutations in genes encoding ciliary proteins.

RECENT FINDINGS

Clinical manifestations of PCD have been expanded to include neonatal respiratory distress and heterotaxy. Measurement of nasal nitric oxide has emerged as a useful screening test for PCD based on the very low levels in PCD (approximately 1/10 of normal values). Genetic testing is emerging for PCD and demonstrates extensive genetic heterogeneity. Some genes and gene mutations involved in PCD have been defined. Approximately one-third of PCD cases have identifiable gene mutations in one of six different genes. An international effort is focused on defining PCD-causing defects in other genes.

SUMMARY

The incorporation of nasal nitric oxide measurement as a screening test to define probable PCD cases and gene mutation analysis to make a definitive diagnosis of PCD should enhance diagnostic evaluation of PCD.

Mutations in radial spoke head protein genes RSPH9 and RSPH4A cause primary ciliary dyskinesia with central-microtubular-pair abnormalities

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous inherited disorder arising from dysmotility of motile cilia and sperm. This is associated with a variety of ultrastructural defects of the cilia and sperm axoneme that affect movement, leading to clinical consequences on respiratory-tract mucociliary clearance and lung function, fertility, and left-right body-axis determination. We performed whole-genome SNP-based linkage analysis in seven consanguineous families with PCD and central-microtubular-pair abnormalities. This identified two loci, in two families with intermittent absence of the central-pair structure (chromosome 6p21.1, Zmax 6.7) and in five families with complete absence of the central pair (chromosome 6q22.1, Zmax 7.0). Mutations were subsequently identified in two positional candidate genes, RSPH9 on chromosome 6p21.1 and RSPH4A on chromosome 6q22.1. Haplotype analysis identified a common ancestral founder effect RSPH4A mutation present in UK-Pakistani pedigrees. Both RSPH9 and RSPH4A encode protein components of the axonemal radial spoke head. In situ hybridization of murine Rsph9 shows gene expression restricted to regions containing motile cilia. Investigation of the effect of knockdown or mutations of RSPH9 orthologs in zebrafish and Chlamydomonas indicate that radial spoke head proteins are important in maintaining normal movement in motile, "9+2"-structure cilia and flagella. This effect is rescued by reintroduction of gene expression for restoration of a normal beat pattern in zebrafish. Disturbance in function of these genes was not associated with defects in left-right axis determination in humans or zebrafish.

DNAI2 mutations cause primary ciliary dyskinesia with defects in the outer dynein arm

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous disorder characterized by chronic destructive airway disease and randomization of left/right body asymmetry. Males often have reduced fertility due to impaired sperm tail function. The complex PCD phenotype results from dysfunction of cilia of the airways and the embryonic node and the structurally related motile sperm flagella. This is associated with underlying ultrastructural defects that frequently involve the outer dynein arm (ODA) complexes that generate cilia and flagella movement. Applying a positional and functional candidate-gene approach, we identified homozygous loss-of-function DNAI2 mutations (IVS11+1G > A) in four individuals from a family with PCD and ODA defects. Further mutational screening of 105 unrelated PCD families detected two distinct homozygous mutations, including a nonsense (c.787C > T) and a splicing mutation (IVS3-3T > G) resulting in out-of-frame transcripts. Analysis of protein expression of the ODA intermediate chain DNAI2 showed sublocalization throughout respiratory cilia. Electron microscopy showed that mutant respiratory cells from these patients lacked DNAI2 protein expression and exhibited ODA defects. High-resolution immunofluorescence imaging demonstrated absence of the ODA heavy chains DNAH5 and DNAH9 from all DNAI2 mutant ciliary axonemes. In addition, we demonstrated complete or distal absence of DNAI2 from ciliary axonemes in respiratory cells of patients with mutations in genes encoding the ODA chains DNAH5 and DNAI1, respectively. Thus, DNAI2 and DNAH5 mutations affect assembly of proximal and distal ODA complexes, whereas DNAI1 mutations mainly disrupt assembly of proximal ODA complexes.