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Neuromuscular diseases (NMDs) affect ∼15 million people globally. In high income settings DNA-based diagnosis has transformed care pathways and led to gene-specific therapies. However, most affected families are in low-to-middle income countries (LMICs) with limited access to DNA-based diagnosis. Most (86%) published genetic data is derived from European ancestry. This marked genetic data inequality hampers understanding of genetic diversity and hinders accurate genetic diagnosis in all income settings. We developed a cloud-based transcontinental partnership to build diverse, deeply-phenotyped and genetically characterized cohorts to improve genetic architecture knowledge, and potentially advance diagnosis and clinical management. We connected 18 centres in Brazil, India, South Africa, Turkey, Zambia, Netherlands and the UK. We co-developed a cloud-based data solution and trained 17 international neurology fellows in clinical genomic data interpretation. Single gene and whole exome data were analysed via a bespoke bioinformatics pipeline and reviewed alongside clinical and phenotypic data in global webinars to inform genetic outcome decisions. We recruited 6001 participants in the first 43 months. Initial genetic analyses 'solved' or 'possibly solved' ∼56% probands overall. In-depth genetic data review of the four commonest clinical categories (limb girdle muscular dystrophy, inherited peripheral neuropathies, congenital myopathy/muscular dystrophies and Duchenne/Becker muscular dystrophy) delivered a ∼59% 'solved' and ∼13% 'possibly solved' outcome. Almost 29% of disease causing variants were novel, increasing diverse pathogenic variant knowledge. Unsolved participants represent a new discovery cohort. The dataset provides a large resource from under-represented populations for genetic and translational research. In conclusion, we established a remote transcontinental partnership to assess genetic architecture of NMDs across diverse populations. It supported DNA-based diagnosis, potentially enabling genetic counselling, care pathways and eligibility for gene-specific trials. Similar virtual partnerships could be adopted by other areas of global genomic neurological practice to reduce genetic data inequality and benefit patients globally. [ABSTRACT FROM AUTHOR]

Motile cilia and flagella beat rhythmically on the surface of cells to power the flow of fluid and to enable spermatozoa and unicellular eukaryotes to swim. In humans, defective ciliary motility can lead to male infertility and a congenital disorder called primary ciliary dyskinesia (PCD), in which impaired clearance of mucus by the cilia causes chronic respiratory infections1. Ciliary movement is generated by the axoneme, a molecular machine consisting of microtubules, ATP-powered dynein motors and regulatory complexes2. The size and complexity of the axoneme has so far prevented the development of an atomic model, hindering efforts to understand how it functions. Here we capitalize on recent developments in artificial intelligence-enabled structure prediction and cryo-electron microscopy (cryo-EM) to determine the structure of the 96-nm modular repeats of axonemes from the flagella of the alga Chlamydomonas reinhardtii and human respiratory cilia. Our atomic models provide insights into the conservation and specialization of axonemes, the interconnectivity between dyneins and their regulators, and the mechanisms that maintain axonemal periodicity. Correlated conformational changes in mechanoregulatory complexes with their associated axonemal dynein motors provide a mechanism for the long-hypothesized mechanotransduction pathway to regulate ciliary motility. Structures of respiratory-cilia doublet microtubules from four individuals with PCD reveal how the loss of individual docking factors can selectively eradicate periodically repeating structures.Detailed atomic models of axonemes from algal flagella and human respiratory cilia, which are hair-like protrusions from cells that enable motility and clear mucus from human airways, could provide insights into how they function. [ABSTRACT FROM AUTHOR]

Primary ciliary dyskinesia (PCD) is a rare genetic condition characterized by chronic respiratory tract infections and in some cases laterality defects and infertility. The symptoms of PCD are caused by malfunction of motile cilia, hairlike organelles protruding out of the cell that are responsible for removal of mucus from the airways and organizing internal organ positioning during embryonic development. PCD is caused by mutations in genes coding for structural or assembly proteins in motile cilia. Thus far mutations in over 50 genes have been identified and these variants explain around 70% of all known cases. Population specific genetics underlying PCD has been reported, thus highlighting the importance of characterizing gene variants in different populations for development of gene-based diagnostics. In this study, we identified a recurrent loss-of-function mutation c.198_200delinsCC in CFAP300 causing lack of the protein product. PCD patients homozygous for the identified CFAP300 mutation have immotile airway epithelial cilia associated with missing dynein arms in their ciliary axonemes. Furthermore, using super resolution microscopy we demonstrate that CFAP300 is transported along cilia in normal human airway epithelial cells suggesting a role for CFAP300 in dynein complex transport in addition to preassembly in the cytoplasm. Our results highlight the importance of CFAP300 in dynein arm assembly and improve diagnostics of PCD in Finland. [ABSTRACT FROM AUTHOR]

Background Primary ciliary dyskinesia (PcD), a genetically heterogeneous condition enriched in some consanguineous populations, results from recessive mutations affecting cilia biogenesis and motility. currently, diagnosis requires multiple expert tests. Methods The diagnostic utility of multigene panel next- generation sequencing (ngs) was evaluated in 161 unrelated families from multiple population ancestries. Results Most (82%) families had affected individuals with biallelic or hemizygous (75%) or single (7%) pathogenic causal alleles in known PcD genes. loss-of-function alleles dominate (73% frameshift, stop- gain, splice site), most (58%) being homozygous, even in non- consanguineous families. although 57% (88) of the total 155 diagnostic disease variants were novel, recurrent mutations and mutated genes were detected. These differed markedly between white european (52% of families carry DNAH5 or DNAH11 mutations), arab (42% of families carry CCDC39 or CCDC40 mutations) and south asian (single LRRC6 or CCDC103 mutations carried in 36% of families) patients, revealing a striking genetic stratification according to population of origin in PcD. genetics facilitated successful diagnosis of 81% of families with normal or inconclusive ultrastructure and 67% missing prior ultrastructure results. Conclusions This study shows the added value of high-throughput targeted ngs in expediting PcD diagnosis. Therefore, there is potential significant patient benefit in wider and/or earlier implementation of genetic screening. [ABSTRACT FROM AUTHOR]

Primary ciliary dyskinesia (PCD) is a rare genetic disorder of motile cilia dysfunction generally inherited as an autosomal recessive disease. Genetic testing is increasingly considered an early step in the PCD diagnostic workflow. We used targeted panel next‐generation sequencing (NGS) for genetic screening of 33 Egyptian families with clinically highly suspected PCD. All variants prioritized were Sanger confirmed in the affected individuals and correctly segregated within the family. Targeted NGS yielded a high diagnostic output (70%) with biallelic mutations identified in known PCD genes. Mutations were identified in 13 genes overall, with CCDC40 and CCDC39 the most frequently mutated genes among Egyptian patients. Most identified mutations were predicted null effect variants (79%) and not reported before (85%). This study reveals that the genetic landscape of PCD among Egyptians is highly heterogeneous, indicating that a targeted NGS approach covering multiple genes will provide a superior diagnostic yield compared to Sanger sequencing for genetic diagnosis. The high diagnostic output achieved here highlights the potential of placing genetic testing early within the diagnostic workflow for PCD, in particular in developing countries where other diagnostic tests can be less available. [ABSTRACT FROM AUTHOR]

Motile cilia move body fluids and gametes and the beating of cilia lining the airway epithelial surfaces ensures that they are kept clear and protected from inhaled pathogens and consequent respiratory infections. Dynein motor proteins provide mechanical force for cilia beating. Dynein mutations are a common cause of primary ciliary dyskinesia (PCD), an inherited condition characterized by deficient mucociliary clearance and chronic respiratory disease coupled with laterality disturbances and subfertility. Using next-generation sequencing, we detected mutations in the ciliary outer dynein arm (ODA) heavy chain gene DNAH9 in individuals from PCD clinics with situs inversus and in one case male infertility. DNAH9 and its partner heavy chain DNAH5 localize to type 2 ODAs of the distal cilium and in DNAH9 -mutated nasal respiratory epithelial cilia we found a loss of DNAH9/DNAH5-containing type 2 ODAs that was restricted to the distal cilia region. This confers a reduced beating frequency with a subtle beating pattern defect affecting the motility of the distal cilia portion. 3D electron tomography ultrastructural studies confirmed regional loss of ODAs from the distal cilium, manifesting as either loss of whole ODA or partial loss of ODA volume. Paramecium DNAH9 knockdown confirms an evolutionarily conserved function for DNAH9 in cilia motility and ODA stability. We find that DNAH9 is widely expressed in the airways, despite DNAH9 mutations appearing to confer symptoms restricted to the upper respiratory tract. In summary, DNAH9 mutations reduce cilia function but some respiratory mucociliary clearance potential may be retained, widening the PCD disease spectrum. [ABSTRACT FROM AUTHOR]

Rationale: Primary ciliary dyskinesia is a genetically heterogeneous inherited condition characterised by progressive lung disease arising from abnormal cilia function. Approximately half of patients have situs inversus. The estimated prevalence of primary ciliary dyskinesia in the UK South Asian population is 1:2265. Early, accurate diagnosis is key to implementing appropriate management but clinical diagnostic tests can be equivocal.Objectives: To determine the importance of genetic screening for primary ciliary dyskinesia in a UK South Asian population with a typical clinical phenotype, where standard testing is inconclusive.Methods: Next-generation sequencing was used to screen 86 South Asian patients who had a clinical history consistent with primary ciliary dyskinesia. The effect of a CCDC103 p.His154Pro missense variant compared with other dynein arm-associated gene mutations on diagnostic/phenotypic variability was tested. CCDC103 p.His154Pro variant pathogenicity was assessed by oligomerisation assay.Results: Sixteen of 86 (19%) patients carried a homozygous CCDC103 p.His154Pro mutation which was found to disrupt protein oligomerisation. Variable diagnostic test results were obtained including normal nasal nitric oxide levels, normal ciliary beat pattern and frequency and a spectrum of partial and normal dynein arm retention. Fifteen (94%) patients or their sibling(s) had situs inversus suggesting CCDC103 p.His154Pro patients without situs inversus are missed.Conclusions: The CCDC103 p.His154Pro mutation is more prevalent than previously thought in the South Asian community and causes primary ciliary dyskinesia that can be difficult to diagnose using pathology-based clinical tests. Genetic testing is critical when there is a strong clinical phenotype with inconclusive standard diagnostic tests. [ABSTRACT FROM AUTHOR]

Primary ciliary dyskinesia (PCD) is associated with abnormal organ positioning (situs) and congenital heart disease (CHD). This study investigated genotype-phenotype associations in PCD to facilitate risk predictions for cardiac and laterality defects. This retrospective cohort study of 389 UK patients with PCD found 51% had abnormal situs and 25% had CHD and/or laterality defects other than situs inversus totalis. Patients with biallelic mutations in a subset of nine PCD genes had normal situs. Patients with consanguineous parents had higher odds of situs abnormalities than patients with non-consanguineous parents. Patients with abnormal situs had higher odds of CHD and/or laterality defects. [ABSTRACT FROM AUTHOR]

Introduction: Primary ciliary dyskinesia (PCD) is a rare genetic disorder characterized by chronic respiratory tract infections and in some cases laterality defects and infertility. The symptoms of PCD are caused by malfunction of motile cilia, hair-like organelles protruding out of the cell. Thus far, disease causing variants in over 50 genes have been identified and these variants explain around 70% of all known cases. Population specific genetics underlying PCD has been reported highlighting the importance of characterizing gene variants in different populations for development of gene-based diagnostics and management., Methods: Whole exome sequencing was used to identify disease causing variants in Finnish PCD cohort. The effect of the identified HYDIN variants on cilia structure and function was confirmed by high-speed video analysis, immunofluorescence and electron tomography., Results: In this study, we identified three Finnish PCD patients carrying homozygous loss-of-function variants and one patient with compound heterozygous variants within HYDIN. The functional studies showed defects in the axonemal central pair complex. All patients had clinical PCD symptoms including chronic wet cough and recurrent airway infections, associated with mostly static airway cilia., Conclusion: Our results are consistent with the previously identified important role of HYDIN in the axonemal central pair complex and improve specific diagnostics of PCD in different national populations., (© 2024 The Author(s). Pediatric Pulmonology published by Wiley Periodicals LLC.)

Neuromuscular diseases (NMDs) affect ∼15 million people globally. In high income settings DNA-based diagnosis has transformed care pathways and led to gene-specific therapies. However, most affected families are in low-to-middle income countries (LMICs) with limited access to DNA-based diagnosis. Most (86%) published genetic data is derived from European ancestry. This marked genetic data inequality hampers understanding of genetic diversity and hinders accurate genetic diagnosis in all income settings. We developed a cloud-based transcontinental partnership to build diverse, deeply-phenotyped and genetically characterized cohorts to improve genetic architecture knowledge, and potentially advance diagnosis and clinical management. We connected 18 centres in Brazil, India, South Africa, Turkey, Zambia, Netherlands and the UK. We co-developed a cloud-based data solution and trained 17 international neurology fellows in clinical genomic data interpretation. Single gene and whole exome data were analysed via a bespoke bioinformatics pipeline and reviewed alongside clinical and phenotypic data in global webinars to inform genetic outcome decisions. We recruited 6001 participants in the first 43 months. Initial genetic analyses 'solved' or 'possibly solved' ∼56% probands overall. In-depth genetic data review of the four commonest clinical categories (limb girdle muscular dystrophy, inherited peripheral neuropathies, congenital myopathy/muscular dystrophies and Duchenne/Becker muscular dystrophy) delivered a ∼59% 'solved' and ∼13% 'possibly solved' outcome. Almost 29% of disease causing variants were novel, increasing diverse pathogenic variant knowledge. Unsolved participants represent a new discovery cohort. The dataset provides a large resource from under-represented populations for genetic and translational research. In conclusion, we established a remote transcontinental partnership to assess genetic architecture of NMDs across diverse populations. It supported DNA-based diagnosis, potentially enabling genetic counselling, care pathways and eligibility for gene-specific trials. Similar virtual partnerships could be adopted by other areas of global genomic neurological practice to reduce genetic data inequality and benefit patients globally., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain.)

Background: Diagnostic testing for primary ciliary dyskinesia (PCD) started in 2013 in Palestine. We aimed to describe the diagnostic, genetic and clinical spectrum of the Palestinian PCD population., Methods: Individuals with symptoms suggestive of PCD were opportunistically considered for diagnostic testing: nasal nitric oxide (nNO) measurement, transmission electron microscopy (TEM) and/or PCD genetic panel or whole-exome testing. Clinical characteristics of those with a positive diagnosis were collected close to testing including forced expiratory volume in 1 s (FEV 1 ) Global Lung Index z-scores and body mass index z-scores., Results: 68 individuals had a definite positive PCD diagnosis, 31 confirmed by genetic and TEM results, 23 by TEM results alone, and 14 by genetic variants alone. 45 individuals from 40 families had 17 clinically actionable variants and four had variants of unknown significance in 14 PCD genes . CCDC39 , DNAH11 and DNAAF11 were the most commonly mutated genes. 100% of variants were homozygous. Patients had a median age of 10.0 years at diagnosis, were highly consanguineous (93%) and 100% were of Arabic descent. Clinical features included persistent wet cough (99%), neonatal respiratory distress (84%) and situs inversus (43%). Lung function at diagnosis was already impaired (FEV 1 z-score median -1.90 (-5.0-1.32)) and growth was mostly within the normal range (z-score mean -0.36 (-3.03-2.57). 19% individuals had finger clubbing., Conclusions: Despite limited local resources in Palestine, detailed geno- and phenotyping forms the basis of one of the largest national PCD populations globally. There was notable familial homozygosity within the context of significant population heterogeneity., Competing Interests: Conflict of interest: N. Rumman received support for the present manuscript from two NIOX MINO devices from Circassia (previously called Aerocrine) to perform nasal nitric oxide testing and AAIR Charity funded whole-exome sequencing testing, and support for attending meetings and/or travel from the European Respiratory Society for a short term research training fellowship (3 months at Southampton University) (STRTF 2014-6816), outside the submitted work. M.R. Fassad received support for the present manuscript from a Wellcome Trust Collaborative Award in Science (210585/Z/18/Z). C. Driessens received support for the present manuscript from NHS England: work for this manuscript was performed while working for the National PCD Diagnostic Service at University Hospital Southampton; this service is commissioned and funded by NHS England. R. Pengelly received support for the present manuscript from Asthma Allergy and Inflammation Research. G. Wheway received support for the present manuscript from Asthma Allergy and Inflammation Research Trust; grants or contracts from UKRI COVID-19 Agile Response Fund, Wessex Medical Research/Rosetrees Trust PhD studentship, and Asthma Allergy and Inflammation Research Trust, outside the submitted work; stock or stock options for Illumina Inc., outside the submitted work; and receipt of equipment, materials, medical writing, gifts or other services from Synthego, outside the submitted work. H.M. Mitchison received support for the present manuscript from Great Ormond Street Children's Charity, NIHR Biomedical Research Centre at Great Ormond Street Hospital, and British Council Newton-Mosharafa Fund and Ministry of Higher Education in Egypt. J.S. Lucas received grants or contracts from NIHR, AAIR Charity, and NHS England, outside the submitted work. The remaining authors have nothing to disclose., (Copyright ©The authors 2023.)

Background: Development of therapeutic approaches for rare respiratory diseases is hampered by the lack of systems that allow medium-to-high-throughput screening of fully differentiated respiratory epithelium from affected patients. This is a particular problem for primary ciliary dyskinesia (PCD), a rare genetic disease caused by mutations in genes that adversely affect ciliary movement and consequently mucociliary transport. Primary cell culture of basal epithelial cells from nasal brush biopsies followed by ciliated differentiation at the air-liquid interface (ALI) has proven to be a useful tool in PCD diagnostics but the technique's broader utility, including in pre-clinical PCD research, has been restricted by the limited number of basal cells that can be expanded from such biopsies., Methods: We describe an immunofluorescence screening method, enabled by extensive expansion of basal cells from PCD patients and the directed differentiation of these cells into ciliated epithelium in miniaturised 96-well transwell format ALI cultures. As proof-of-principle, we performed a personalised investigation in a patient with a rare and severe form of PCD (reduced generation of motile cilia), in this case caused by a homozygous nonsense mutation in the MCIDAS gene., Results: Initial analyses of ciliary ultrastructure, beat pattern and beat frequency in the 96-well transwell format ALI cultures indicate that a range of different PCD defects can be retained in these cultures. The screening system in our proof-of-principal investigation allowed drugs that induce translational readthrough to be evaluated alone or in combination with nonsense-mediated decay inhibitors. We observed restoration of basal body formation but not the generation of cilia in the patient's nasal epithelial cells in vitro. CONCLUSION: Our study provides a platform for higher throughput analyses of airway epithelia that is applicable in a range of settings and suggests novel avenues for drug evaluation and development in PCD caused by nonsense mutations., Competing Interests: Conflict of interest: D.D.H. Lee has nothing to disclose. Conflict of interest: D. Cardinale has nothing to disclose. Conflict of interest: E. Nigro has nothing to disclose. Conflict of interest: C.R. Butler has nothing to disclose. Conflict of interest: A. Rutman has nothing to disclose. Conflict of interest: M.R. Fassad has nothing to disclose. Conflict of interest: R.A. Hirst has nothing to disclose. Conflict of interest: D. Moulding has nothing to disclose. Conflict of interest: A. Agrotis has nothing to disclose. Conflict of interest: E. Forsythe has nothing to disclose. Conflict of interest: D. Peckham has nothing to disclose. Conflict of interest: E. Robson has nothing to disclose. Conflict of interest: C.M. Smith has nothing to disclose. Conflict of interest: S. Somavarapu has nothing to disclose. Conflict of interest: P.L. Beales has nothing to disclose. Conflict of interest: S.L. Hart has nothing to disclose. Conflict of interest: S.M. Janes has nothing to disclose. Conflict of interest: H.M. Mitchison has nothing to disclose. Conflict of interest: R. Ketteler has nothing to disclose. Conflict of interest: R.E. Hynds has nothing to disclose. Conflict of interest: C. O'Callaghan has nothing to disclose., (Copyright ©The authors 2021.)

Background: Primary ciliary dyskinesia (PCD) is a heterogeneous inherited disorder caused by mutations in approximately 50 cilia-related genes. PCD genotype-phenotype relationships have mostly arisen from small case series because existing statistical approaches to investigating relationships have been unsuitable for rare diseases., Methods: We applied a topological data analysis (TDA) approach to investigate genotype-phenotype relationships in PCD. Data from separate training and validation cohorts included 396 genetically defined individuals carrying pathogenic variants in PCD genes. To develop the TDA models, 12 clinical and diagnostic variables were included. TDA-driven hypotheses were subsequently tested using traditional statistics., Results: Disease severity at diagnosis, measured by forced expiratory volume in 1 s (FEV 1 ) z-score, was significantly worse in individuals with CCDC39 mutations (compared to other gene mutations) and better in those with DNAH11 mutations; the latter also reported less neonatal respiratory distress. Patients without neonatal respiratory distress had better preserved FEV 1 at diagnosis. Individuals with DNAH5 mutations were phenotypically diverse. Cilia ultrastructure and beat pattern defects correlated closely to specific causative gene groups, confirming these tests can be used to support a genetic diagnosis., Conclusions: This large scale, multi-national study presents PCD as a syndrome with overlapping symptoms and variations in phenotype according to genotype. TDA modelling confirmed genotype-phenotype relationships reported by smaller studies ( e.g. FEV 1 worse with CCDC39 mutation) and identified new relationships, including FEV 1 preservation with DNAH11 mutations and diversity of severity with DNAH5 mutations., Competing Interests: Conflict of interest: B. Rubbo has nothing to disclose. Conflict of interest: M. Legendre has nothing to disclose. Conflict of interest: M.R. Fassad has nothing to disclose. Conflict of interest: E.G. Haarman has nothing to disclose. Conflict of interest: S. Best has nothing to disclose. Conflict of interest: I.C.M. Bon has nothing to disclose. Conflict of interest: J. Brandsma has nothing to disclose. Conflict of interest: P-R. Burgel reports personal fees for lectures and advisory board work from AstraZeneca, Boehringer Ingelheim, Chiesi, Novartis, Teva and Vertex, as well as personal fees for lectures from GSK, Pfizer and Zambon, outside the submitted work. Conflict of interest: G. Carlsson has nothing to disclose. Conflict of interest: S.B. Carr reports non-financial support and other (advisory board, lecture fee, travel, steering committee) from Vertex Pharmaceuticals, other (advisory board) from Profile Pharmaceuticals and other (lectures) from Teva Pharmaceuticals, as well as non-financial support and other (advisory board, travel, accommodation) from Chiesi Pharmaceuticals, outside the submitted work. Conflict of interest: M. Carroll has nothing to disclose. Conflict of interest: M. Edwards has nothing to disclose. Conflict of interest: E. Escudier has nothing to disclose. Conflict of interest: I. Honoré has nothing to disclose. Conflict of interest: D. Hunt has nothing to disclose. Conflict of interest: G. Jouvion has nothing to disclose. Conflict of interest: M.R. Loebinger reports personal fees for advisory board work and consultancy from AstraZeneca, Insmed, Polyphor, Bayer and Griffols, outside the submitted work. Conflict of interest: B. Maitre has nothing to disclose. Conflict of interest: D. Morris-Rosendahl has nothing to disclose. Conflict of interest: J-F. Papon has nothing to disclose. Conflict of interest: C.M. Parsons has nothing to disclose. Conflict of interest: M.P. Patel has nothing to disclose. Conflict of interest: N.S. Thomas has nothing to disclose. Conflict of interest: G. Thouvenin has nothing to disclose. Conflict of interest: W.T. Walker has nothing to disclose. Conflict of interest: R. Wilson has nothing to disclose. Conflict of interest: C. Hogg has nothing to disclose. Conflict of interest: H.M. Mitchison has nothing to disclose. Conflict of interest: J.S. Lucas has nothing to disclose. Conflict of interest: A. Shoemark has nothing to disclose., (Copyright ©The authors 2021. For reproduction rights and permissions contact permissions@ersnet.org.)

Purpose: To describe our experience with a large cohort (411 patients from 288 families) of various forms of skeletal dysplasia who were molecularly characterized., Methods: Detailed phenotyping and next-generation sequencing (panel and exome)., Results: Our analysis revealed 224 pathogenic/likely pathogenic variants (54 (24%) of which are novel) in 123 genes with established or tentative links to skeletal dysplasia. In addition, we propose 5 genes as candidate disease genes with suggestive biological links (WNT3A, SUCO, RIN1, DIP2C, and PAN2). Phenotypically, we note that our cohort spans 36 established phenotypic categories by the International Skeletal Dysplasia Nosology, as well as 18 novel skeletal dysplasia phenotypes that could not be classified under these categories, e.g., the novel C3orf17-related skeletal dysplasia. We also describe novel phenotypic aspects of well-known disease genes, e.g., PGAP3-related Toriello-Carey syndrome-like phenotype. We note a strong founder effect for many genes in our cohort, which allowed us to calculate a minimum disease burden for the autosomal recessive forms of skeletal dysplasia in our population (7.16E-04), which is much higher than the global average., Conclusion: By expanding the phenotypic, allelic, and locus heterogeneity of skeletal dysplasia in humans, we hope our study will improve the diagnostic rate of patients with these conditions.

Primary ciliary dyskinesia (PCD) is a genetically and phenotypically heterogeneous disorder characterized by destructive respiratory disease and laterality abnormalities due to randomized left-right body asymmetry. PCD is mostly caused by mutations affecting the core axoneme structure of motile cilia that is essential for movement. Genes that cause PCD when mutated include a group that encode proteins essential for the assembly of the ciliary dynein motors and the active transport process that delivers them from their cytoplasmic assembly site into the axoneme. We screened a cohort of affected individuals for disease-causing mutations using a targeted next generation sequencing panel and identified two unrelated families (three affected children) with mutations in the uncharacterized C11orf70 gene (official gene name CFAP300). The affected children share a consistent PCD phenotype from early life with laterality defects and immotile respiratory cilia displaying combined loss of inner and outer dynein arms (IDA+ODA). Phylogenetic analysis shows C11orf70 is highly conserved, distributed across species similarly to proteins involved in the intraflagellar transport (IFT)-dependant assembly of axonemal dyneins. Paramecium C11orf70 RNAi knockdown led to combined loss of ciliary IDA+ODA with reduced cilia beating and swim velocity. Tagged C11orf70 in Paramecium and Chlamydomonas localizes mainly in the cytoplasm with a small amount in the ciliary component. IFT139/TTC21B (IFT-A protein) and FLA10 (IFT kinesin) depletion experiments show that its transport within cilia is IFT dependent. During ciliogenesis, C11orf70 accumulates at the ciliary tips in a similar distribution to the IFT-B protein IFT46. In summary, C11orf70 is essential for assembly of dynein arms and C11orf70 mutations cause defective cilia motility and PCD., (Copyright © 2018 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Background & Aim: Hearing loss is the most frequent form of neurosensory deficit in humans. Although the majority of hereditary hearing loss is due to nuclear gene mutations, it has become clear the significant contribution of mitochondrial genes. The first mitochondrial mutation shown to cause non-syndromic hearing loss in humans was the A1555G mutation in the small ribosomal RNA gene (12S rRNA). It has been detected in hundreds of families of different ethnic backgrounds, making it one of the prevalent genetic causes of hearing loss currently identified. However, there are major differences between ethnic groups regarding the frequency of this mutation. Few studies have been made in Arab countries, especially in Egypt. Here we report the prevalence of the mitochondrial mutation A1555G among patients with non-syndromic hearing loss (NSHL) and in healthy individuals with normal hearing in the Egyptian population., Subjects & Methods: The study was conducted on 97 patients with SNHL and 300 unrelated healthy Egyptian individuals, with normal hearing, as normal control subjects. Polymerase chain reaction followed by restriction enzyme digestion was used to screen the DNA samples of all subjects for the A1555G mutation., Results: Participants included 97 cases with SNHL, 46 males and 51 females. Their ages ranged from 1 month to 65 years with the mean age 6.2 years (SD ± 8.2). Paternal consanguinity was reported in 46% (35/76) of the studied families. The A1555G mutation was found in one of the 97 patients (1.3%), while it has not been detected in the 300 control samples., Conclusion: Our findings indicate that, even in absence of exposure to aminoglycosides, the mitochondrial A1555G mutation is one of the potential causes of non-syndromic SNHL in the Egyptian population.