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Mutations in the N-terminal WD40 domain of coatomer protein complex subunit α (COPA) cause a type I interferonopathy, typically characterized by alveolar hemorrhage, arthritis, and nephritis. We described 3 heterozygous mutations in the C-terminal domain (CTD) of COPA (p.C1013S, p.R1058C, and p.R1142X) in 6 children from 3 unrelated families with a similar syndrome of autoinflammation and autoimmunity. We showed that these CTD COPA mutations disrupt the integrity and the function of coat protein complex I (COPI). In COPAR1142X and COPAR1058C fibroblasts, we demonstrated that COPI dysfunction causes both an anterograde ER-to-Golgi and a retrograde Golgi-to-ER trafficking defect. The disturbed intracellular trafficking resulted in a cGAS/STING-dependent upregulation of the type I IFN signaling in patients and patient-derived cell lines, albeit through a distinct molecular mechanism in comparison with mutations in the WD40 domain of COPA. We showed that CTD COPA mutations induce an activation of ER stress and NF-κB signaling in patient-derived primary cell lines. These results demonstrate the importance of the integrity of the CTD of COPA for COPI function and homeostatic intracellular trafficking, essential to ER homeostasis. CTD COPA mutations result in disease by increased ER stress, disturbed intracellular transport, and increased proinflammatory signaling.

Whereas truncating variants of the giant protein Titin (TTNtv) are the main cause of familial dilated cardiomyopathy (DCM), recently Filamin C truncating variants (FLNCtv) were identified as a cause of arrhythmogenic cardiomyopathy (ACM). Our aim was to characterize and compare clinical and MRI features of TTNtv and FLNCtv in the Belgian population. In index patients referred for genetic testing of ACM/DCM, FLNCtv and TTNtv were found in 17 (3.6%) and 33 (12.3%) subjects, respectively. Further family cascade screening yielded 24 and 19 additional truncating variant carriers in FLNC and TTN, respectively. The main phenotype was ACM in FLNCtv carriers whereas TTNtv carriers showed either an ACM or DCM phenotype. Non-sustained Ventricular Tachycardia was frequent in both populations. MRI data, available in 28/40 FLNCtv and 32/52 TTNtv patients, showed lower Left Ventricular (LV) ejection fraction and lower LV strain in TTNtv patients (p < 0.01). Conversely, both the frequency (68% vs 22%) and extent of non-ischemic myocardial late gadolinium enhancement (LGE) was significantly higher in FLNCtv patients (p < 0.01). Hereby, ring-like LGE was found in 16/19 (84%) FLNCtv versus 1/7 (14%) of TTNtv patients (p < 0.01). In conclusion, a large number of FLNCtv and TTNtv patients present with an ACM phenotype but can be separated by cardiac MRI. Whereas FLNCtv patients often have extensive myocardial fibrosis, typically following a ring-like pattern, LV dysfunction without or limited replacement fibrosis is the common TTNtv phenotype., (© 2023. The Author(s), under exclusive licence to European Society of Human Genetics.)

Background: The international study ThromboGenomics has evaluated the diagnostic rate using a targeted multigene panel test for the screening of inherited bleeding, thrombotic and platelet disorders., Objectives: We retrospectively analyzed the results of the implementation of genetic testing for inherited bleeding, thrombotic and platelet disorders in Belgian clinical practice and evaluated possible reclassification of reported variants., Patients/methods: We implemented a Thrombosis-Hemostasis multigene panel test using whole exome sequencing to diagnose 487 patients recruited by 27 different Belgian hospitals with the implementation of stringent laboratory accreditation standards and by studying up to 100 diagnostic-grade genes., Results: This Thrombosis-Hemostasis multigene panel test was able to detect at least one genetic variant in 58% of the 487 patients of which 50% were (likely) pathogenic variants and the others were variants of unknown significance. Polygenic variants were detected in 65 patients (13%). A multi-step workflow for results discussion by multidisciplinary team meetings and patients' recalls for segregation studies and additional laboratory testing was set up. Variants were also submitted to the GoldVariants database from the International Society on Thrombosis and Haemostasis (ISTH). The aim of these approaches is to optimize variant interpretation and to (re)classify variants of unknown significance as (likely) pathogenic or (likely) benign., Conclusions: The growing implementation of multigene panel tests in clinical diagnostics comes with difficulties in interpreting genetic results. Additional efforts are needed to continuously optimize the diagnostic outcome., Competing Interests: Declaration of competing interest All authors declare they have no conflict of interest to disclose., (Copyright © 2022 International Society on Thrombosis and Haemostasis. Published by Elsevier Inc. All rights reserved.)

Encephalitis and encephalopathy in children represent a diagnostic challenge. We describe a patient with relapsing encephalitis in whom the differential diagnosis included acute disseminated encephalomyelitis, human herpesvirus 6 encephalitis, and hemophagocytic lymphohistiocytosis (HLH). Because of its rarity, HLH is often overlooked as a differential diagnosis in encephalitis, especially in the isolated CNS forms. As this case illustrates, inborn errors of immunity can underlie isolated encephalitis and should be included in the differential diagnosis of these presentations., (© 2022 American Academy of Neurology.)

NFKB1 haploinsufficiengcy was first described in 2015 in three families with common variable immunodeficiency (CVID), presenting heterogeneously with symptoms of increased infectious susceptibility, skin lesions, malignant lymphoproliferation and autoimmunity. The described mutations all led to a rapid degradation of the mutant protein, resulting in a p50 haploinsufficient state. Since then, more than 50 other mutations have been reported, located throughout different domains of NFKB1 with the majority situated in the N-terminal Rel homology domain (RHD). The clinical spectrum has also expanded with possible disease manifestations in almost any organ system. In silico prediction tools are often used to estimate the pathogenicity of NFKB1 variants but to prove causality between disease and genetic findings, further downstream functional validation is required. In this report, we studied 2 families with CVID and two novel variants in NFKB1 (c.1638-2A>G and c.787G>C). Both mutations affected mRNA and/or protein expression of NFKB1 and resulted in excessive NLRP3 inflammasome activation in patient macrophages and upregulated interferon stimulated gene expression. Protein-protein interaction analysis demonstrated a loss of interaction with NFKB1 interaction partners for the p.V263L mutation. In conclusion, we proved pathogenicity of two novel variants in NFKB1 in two families with CVID characterized by variable and incomplete penetrance., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Staels, De Keukeleere, Kinnunen, Keskitalo, Lorenzetti, Vanmeert, Prezzemolo, Pasciuto, Lescrinier, Bossuyt, Gerbaux, Willemsen, Neumann, Van Loo, Corveleyn, Willekens, Stalmans, Meyts, Liston, Humblet-Baron, Seppänen, Varjosalo and Schrijvers.)

Brugada syndrome (BrS) is a cardiac arrhythmia disorder associated with sudden death in young adults. With the exception of SCN5A, encoding the cardiac sodium channel Na V 1.5, susceptibility genes remain largely unknown. Here we performed a genome-wide association meta-analysis comprising 2,820 unrelated cases with BrS and 10,001 controls, and identified 21 association signals at 12 loci (10 new). Single nucleotide polymorphism (SNP)-heritability estimates indicate a strong polygenic influence. Polygenic risk score analyses based on the 21 susceptibility variants demonstrate varying cumulative contribution of common risk alleles among different patient subgroups, as well as genetic associations with cardiac electrical traits and disorders in the general population. The predominance of cardiac transcription factor loci indicates that transcriptional regulation is a key feature of BrS pathogenesis. Furthermore, functional studies conducted on MAPRE2, encoding the microtubule plus-end binding protein EB2, point to microtubule-related trafficking effects on Na V 1.5 expression as a new underlying molecular mechanism. Taken together, these findings broaden our understanding of the genetic architecture of BrS and provide new insights into its molecular underpinnings., (© 2022. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Genetic testing for pathogenic COL4A3-5 variants is usually undertaken to investigate the cause of persistent hematuria, especially with a family history of hematuria or kidney function impairment. Alport syndrome experts now advocate genetic testing for persistent hematuria, even when a heterozygous pathogenic COL4A3 or COL4A4 is suspected, and cascade testing of their first-degree family members because of their risk of impaired kidney function. The experts recommend too that COL4A3 or COL4A4 heterozygotes do not act as kidney donors. Testing for variants in the COL4A3-COL4A5 genes should also be performed for persistent proteinuria and steroid-resistant nephrotic syndrome due to suspected inherited FSGS and for familial IgA glomerulonephritis and kidney failure of unknown cause., (Copyright © 2022 by the American Society of Nephrology.)

The recent Chandos House meeting of the Alport Variant Collaborative extended the indications for screening for pathogenic variants in the COL4A5, COL4A3 and COL4A4 genes beyond the classical Alport phenotype (haematuria, renal failure; family history of haematuria or renal failure) to include persistent proteinuria, steroid-resistant nephrotic syndrome, focal and segmental glomerulosclerosis (FSGS), familial IgA glomerulonephritis and end-stage kidney failure without an obvious cause. The meeting refined the ACMG criteria for variant assessment for the Alport genes (COL4A3-5). It identified 'mutational hotspots' (PM1) in the collagen IV α5, α3 and α4 chains including position 1 Glycine residues in the Gly-X-Y repeats in the intermediate collagenous domains; and Cysteine residues in the carboxy non-collagenous domain (PP3). It considered that 'well-established' functional assays (PS3, BS3) were still mainly research tools but sequencing and minigene assays were commonly used to confirm splicing variants. It was not possible to define the Minor Allele Frequency (MAF) threshold above which variants were considered Benign (BA1, BS1), because of the different modes of inheritances of Alport syndrome, and the occurrence of hypomorphic variants (often Glycine adjacent to a non-collagenous interruption) and local founder effects. Heterozygous COL4A3 and COL4A4 variants were common 'incidental' findings also present in normal reference databases. The recognition and interpretation of hypomorphic variants in the COL4A3-COL4A5 genes remains a challenge., (© 2021. The Author(s).)

Background: Participation in quality controls, also called external quality assessment (EQA) schemes, is required for the ISO15189 accreditation of the Medical Centers of Human Genetics. However, directives on the minimal frequency of participation in genetic quality control schemes are lacking or too heterogeneous, with a possible impact on health care quality., Objective: The aim of this project is to develop Belgian guidelines on the frequency of participation in quality controls for genetic testing in the context of rare diseases., Methods: A group of experts analyzed 90 EQA schemes offered by accredited providers and focused on analyses used for the diagnosis of rare diseases. On that basis, the experts developed practical recommendations about the minimal frequencies of participation of the Medical Centers of Human Genetics in quality controls and how to deal with poor performances and change management. These guidelines were submitted to the Belgian Accreditation Body and then reviewed and approved by the Belgian College of Human Genetics and Rare Diseases and by the National Institute for Health and Disability Insurance., Results: The guidelines offer a decisional algorithm for the minimal frequency of participation in human genetics EQA schemes. This algorithm has been developed taking into account the scopes of the EQA schemes, the levels of experience, and the annual volumes of the Centers of Human Genetics in the performance of the tests considered. They include three key principles: (1) the recommended annual assessment of all genetic techniques and technological platforms, if possible through EQAs covering the technique, genotyping, and clinical interpretation; (2) the triennial assessment of the genotyping and interpretation of specific germline mutations and pharmacogenomics analyses; and (3) the documentation of actions undertaken in the case of poor performances and the participation to quality control the following year. The use of a Bayesian statistical model has been proposed to help the Centers of Human Genetics to determine the theoretical number of tests that should be annually performed to achieve a certain threshold of performance (eg, a maximal error rate of 1%). Besides, the guidelines insist on the role and responsibility of the national public health authorities in the follow-up of the quality of analyses performed by the Medical Centers of Human Genetics and in demonstrating the cost-effectiveness and rationalization of participation frequency in these quality controls., Conclusions: These guidelines have been developed based on the analysis of a large panel of EQA schemes and data collected from the Belgian Medical Centers of Human Genetics. They are applicable to other countries and will facilitate and improve the quality management and financing systems of the Medical Centers of Human Genetics., (©Joséphine Lantoine, Anne Brysse, Vinciane Dideberg, Kathleen Claes, Sofie Symoens, Wim Coucke, Valérie Benoit, Sonia Rombout, Martine De Rycke, Sara Seneca, Lut Van Laer, Wim Wuyts, Anniek Corveleyn, Kris Van Den Bogaert, Catherine Rydlewski, Françoise Wilkin, Marie Ravoet, Elodie Fastré, Arnaud Capron, Nathalie Monique Vandevelde. Originally published in JMIR Medical Informatics (https://medinform.jmir.org), 12.07.2021.)

Aims: We identified the first Belgian SCN5A founder mutation, c.4813 + 3&#95;4813 + 6dupGGGT. To describe the clinical spectrum and disease severity associated with this mutation, clinical data of 101 SCN5A founder mutation carriers and 46 non-mutation carrying family members from 25 Belgian families were collected., Methods and Results: The SCN5A founder mutation was confirmed by haplotype analysis. The clinical history and electrocardiographic parameters of the mutation carriers and their family members were gathered and compared. A cardiac electrical abnormality was observed in the majority (82%) of the mutation carriers. Cardiac conduction defects, defined as PR or QRS prolongation on electrocardiogram (ECG), were most frequent, occurring in 65% of the mutation carriers. Brugada syndrome (BrS) was the second most prevalent phenotype identified in 52%, followed by atrial dysrythmia in 11%. Overall, 33% of tested mutation carriers had a normal sodium channel blocker test. Negative tests were more common in family members distantly related to the proband. Overall, 23% of the mutation carriers were symptomatic, with 8% displaying major adverse events. As many as 13% of the patients tested with a sodium blocker developed ventricular arrhythmia. One family member who did not carry the founder mutation was diagnosed with BrS., Conclusion: The high prevalence of symptoms and sensitivity to sodium channel blockers in our founder population highlights the adverse effect of the founder mutation on cardiac conduction. The large phenotypical heterogeneity, variable penetrance, and even non-segregation suggest that other genetic (and environmental) factors modify the disease expression, severity, and outcome in these families., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

Purpose: Stringent variant interpretation guidelines can lead to high rates of variants of uncertain significance (VUS) for genetically heterogeneous disease like long QT syndrome (LQTS) and Brugada syndrome (BrS). Quantitative and disease-specific customization of American College of Medical Genetics and Genomics/Association for Molecular Pathology (ACMG/AMP) guidelines can address this false negative rate., Methods: We compared rare variant frequencies from 1847 LQTS (KCNQ1/KCNH2/SCN5A) and 3335 BrS (SCN5A) cases from the International LQTS/BrS Genetics Consortia to population-specific gnomAD data and developed disease-specific criteria for ACMG/AMP evidence classes-rarity (PM2/BS1 rules) and case enrichment of individual (PS4) and domain-specific (PM1) variants., Results: Rare SCN5A variant prevalence differed between European (20.8%) and Japanese (8.9%) BrS patients (p = 5.7 × 10 -18 ) and diagnosis with spontaneous (28.7%) versus induced (15.8%) Brugada type 1 electrocardiogram (ECG) (p = 1.3 × 10 -13 ). Ion channel transmembrane regions and specific N-terminus (KCNH2) and C-terminus (KCNQ1/KCNH2) domains were characterized by high enrichment of case variants and >95% probability of pathogenicity. Applying the customized rules, 17.4% of European BrS and 74.8% of European LQTS cases had (likely) pathogenic variants, compared with estimated diagnostic yields (case excess over gnomAD) of 19.2%/82.1%, reducing VUS prevalence to close to background rare variant frequency., Conclusion: Large case-control data sets enable quantitative implementation of ACMG/AMP guidelines and increased sensitivity for inherited arrhythmia genetic testing.

Background: Familial dilated cardiomyopathy (DCM) is genetically heterogeneous and is associated with mutations in at least 40 different genes. Apart from TTN encoding the giant protein Titin, none of these genes have an expected diagnostic yield of more than 5% complicating genetic diagnosis. Whole exome sequencing (WES) is a powerful alternative for the identification of the causal gene, however variant interpretation remains challenging. We report on WES in a large family with autosomal dominant DCM complicated by end stage heart failure and non-sustained ventricular arrhythmias in whom no causative mutation was identified using a targeted gene panel including 28 genes. Methods and results: WES was applied on 2 affected cousins. Stringent filtering of the identified genetic variants was performed including population variant frequencies, in silico analysis, orthologous and paralogous conservation. Subsequently Sanger sequencing was performed for 10 potential disease causing variants in order to confirm the presence of the variant and to evaluate co-segregation. Only one variant in exon 9 of the RBM20 gene (c.2714T > A, p.Met950Lys, NM&#95;001334363) showed full co-segregation in the 7 affected family members resulting in a maximum 2-point LOD score of 2.1 and suggesting this as the pathogenic mutation responsible for the phenotype. Recently mutations in RBM20 have been linked to arrhythmogenic dilated cardiomyopathy caused by defective splicing of the giant sarcomere protein titin and abnormal calcium handling. Conclusions: We report the identification of a novel mutation in RBM20 by WES in a large pedigree with DCM.

STING-associated vasculopathy with onset in infancy (SAVI) is an autosomal dominant disorder due to gain-of-function mutations in STING1 , also known as TMEM173 , encoding for STING. It was reported as a vasculopathy of infancy. However, since its description a wider spectrum of associated manifestations and disease-onset has been observed. We report a kindred with a heterozygous STING mutation (p.V155M) in which the 19-year-old proband suffered from isolated adult-onset ANCA-associated vasculitis. His father suffered from childhood-onset pulmonary fibrosis and renal failure attributed to ANCA-associated vasculitis, and died at the age of 30 years due to respiratory failure. In addition, an overview of the phenotypic spectrum of SAVI is provided highlighting (a) a high phenotypic variability with in some cases isolated manifestations, (b) the potential of adult-onset disease, and (c) a novel manifestation with ANCA-associated vasculitis., (Copyright © 2020 Staels, Betrains, Doubel, Willemsen, Cleemput, Vanderschueren, Corveleyn, Meyts, Sprangers, Crow, Humblet-Baron, Liston and Schrijvers.)

In medicine, not everything is what it seems and sometimes you need all the pieces of the puzzle in order to complete the diagnosis. This is a case of a disease with two different faces and a review of its respiratory impact. https://bit.ly/2SDKwE5., Competing Interests: Conflict of interest: M. Vandebotermet has nothing to disclose. Conflict of interest: F. Staels has nothing to disclose. Conflict of interest: S. Giovannozzi has nothing to disclose. Conflict of interest: M. Delforge has nothing to disclose. Conflict of interest: T. Tousseyn has nothing to disclose. Conflict of interest: T. Steelandt has nothing to disclose. Conflict of interest: A. Corveleyn has nothing to disclose. Conflict of interest: I. Meyts has nothing to disclose. Conflict of interest: J. Maertens has nothing to disclose. Conflict of interest: J. Yserbyt has nothing to disclose. Conflict of interest: R. Schrijvers has nothing to disclose., (Copyright ©ERS 2020.)

The application of next-generation sequencing to fetal pathology has proved to increase the diagnostic yield in fetuses with abnormal ultrasounds. We retrospectively reviewed genetic data of 30 selected cases studied through targeted resequencing of OMIM genes. In our experience, clinical data proved to be essential to support diagnostic reasoning and enhance variants' assessment. The molecular diagnosis was reached in 19/30 (63%) cases. Only in 7/19 cases the molecular diagnosis confirmed the initial diagnostic hypothesis, showing the relevance of the genotype-first approach. According to the genotype-phenotype correlation, we were able to divide the solved cases into three groups: i) the correlation is well established but it was missed due to lack of specificity, unusual presentation or recent description; ii) the clinical presentation is much more severe than currently known for the underlying condition; iii) the correlation does not recapitulate the entire phenotype, possibly due to the fetal presentation or multiple coexisting conditions. Moreover, we found a higher proportion of recessive diagnosis in abnormal fetuses compared to cohorts of individuals with developmental delay. Our findings suggest that fetal pathology may be enriched in rare alleles and/or in unusual combinations, counter-selected in postnatal genomes and thus contributing to both phenotypic extremeness and atypical presentation., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Knowledge on the influence of specific genotypes on the phenotypic expression of hypertrophic cardiomyopathy (HCM) is emerging. The objective of this study was to evaluate the genotype-phenotype relation in HCM patients and to construct a score to predict the genetic yield based to improve counseling. Unrelated HCM patients who underwent genetic testing were included in the analysis. Multivariate logistic regression was performed to identify variables that predict a positive genetic test. A weighted score was constructed based on the odds ratios. In total, 378 HCM patients were included of whom 141 carried a mutation (global yield 37%), 181 were mutation negative and 56 only carried a variant of unknown significance. We identified age at diagnosis <45 years, familial HCM, familial sudden death, arrhythmic syncope, maximal wall thickness ≥20 mm, asymmetrical hypertrophy and the absence of negative T waves in the lateral ECG leads as significant predictors of a positive genetic test. When we included these values in a risk score we found very high correlation between the score and the observed genetic yield (Pearson r = 0.98). MYBPC3 mutation carriers more frequently suffered sudden cardiac death compared to troponin complex mutations carriers (p = 0.01) and a similar trend was observed compared to MYH7 mutation carriers (p = 0.08) and mutation negative patients (p = 0.11). To conclude, a simple score system based on clinical variables can predict the genetic yield in HCM index patients, aiding in counseling HCM patients. MYBPC3 mutation carriers had a worse outcome regarding sudden cardiac death., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Pathogenic variants in the BCAP31 gene have recently been associated with a severe congenital neurological phenotype, named DDCH after its key features: deafness, dystonia and central hypomyelination. BCAP31 is located at the Xq28 chromosomal region and only male individuals are currently known to be affected, the pathogenic variant being usually transmitted by healthy mothers. Here, we describe a three-year-old male child referred for severe developmental delay, failure to thrive, hearing loss and dyskinetic movements. After a conventional diagnostic workflow, including a normal array-CGH, a tentative diagnosis of dyskinetic cerebral palsy was retained. Clinical exome sequencing in the trio identified a small intragenic deletion in exon 8 of BCAP31, c.709&#95;721del (p.Val237Trpfs*69), originated de novo and not previously reported. Based on the ACMG variant classification, this variant is predicted to be 'likely pathogenic'. Given the consistent phenotypical overlap with the subjects already ascertained with DDCH, we considered this variant to be clinically relevant for this child and causative of his condition., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Congenital disorders of glycosylation (CDG) are a group of rare metabolic diseases, due to impaired protein and lipid glycosylation. We identified two patients with defective serum transferrin glycosylation and mutations in the MAGT1 gene. These patients present with a phenotype that is mainly characterized by intellectual and developmental disability. MAGT1 has been described to be a subunit of the oligosaccharyltransferase (OST) complex and more specifically of the STT3B complex. However, it was also claimed that MAGT1 is a magnesium (Mg 2+ ) transporter. So far, patients with mutations in MAGT1 were linked to a primary immunodeficiency, characterized by chronic EBV infections attributed to a Mg 2+ homeostasis defect (XMEN). We compared the clinical and cellular phenotype of our two patients to that of an XMEN patient that we recently identified. All three patients have an N -glycosylation defect, as was shown by the study of different substrates, such as GLUT1 and SHBG, demonstrating that the posttranslational glycosylation carried out by the STT3B complex is dysfunctional in all three patients. Moreover, MAGT1 deficiency is associated with an enhanced expression of TUSC3, the homolog protein of MAGT1, pointing toward a compensatory mechanism. Hence, we delineate MAGT1-CDG as a disorder associated with two different clinical phenotypes caused by defects in glycosylation., Competing Interests: The authors declare no conflict of interest.

DOCK2 is a guanine-nucleotide-exchange factor for Rac proteins. Activated Rac serves various cellular functions including the reorganization of the actin cytoskeleton in lymphocytes and neutrophils and production of reactive oxygen species in neutrophils. Since 2015, six unrelated patients with combined immunodeficiency and early-onset severe viral infections caused by bi-allelic loss-of-function mutations in DOCK2 have been described. Until now, the function of phagocytes, specifically neutrophils, has not been assessed in human DOCK2 deficiency. Here, we describe a new kindred with four affected siblings harboring a homozygous splice-site mutation (c.2704-2 A > C) in DOCK2. The mutation results in alternative splicing and a complete loss of DOCK2 protein expression. The patients presented with leaky severe combined immunodeficiency or Omenn syndrome. The novel mutation affects EBV-B cell migration and results in NK cell dysfunction similar to previous observations. Moreover, both cytoskeletal rearrangement and reactive oxygen species production are partially impaired in DOCK2-deficient neutrophils.

Deletions on chromosome 15q14 are a known chromosomal cause of cleft palate, typically co-occurring with intellectual disability, facial dysmorphism, and congenital heart defects. The identification of patients with loss-of-function variants in MEIS2, a gene within this deletion, suggests that these features are attributed to haploinsufficiency of MEIS2. To further delineate the phenotypic spectrum of the MEIS2-related syndrome, we collected 23 previously unreported patients with either a de novo sequence variant in MEIS2 (9 patients), or a 15q14 microdeletion affecting MEIS2 (14 patients). All but one de novo MEIS2 variant were identified by whole-exome sequencing. One variant was found by targeted sequencing of MEIS2 in a girl with a clinical suspicion of this syndrome. In addition to the triad of palatal defects, heart defects, and developmental delay, heterozygous loss of MEIS2 results in recurrent facial features, including thin and arched eyebrows, short alae nasi, and thin vermillion. Genotype-phenotype comparison between patients with 15q14 deletions and patients with sequence variants or intragenic deletions within MEIS2, showed a higher prevalence of moderate-to-severe intellectual disability in the former group, advocating for an independent locus for psychomotor development neighboring MEIS2.

Introduction: Loss-of-function (LoF) mutations in the SCN5A gene cause multiple phenotypes including Brugada Syndrome (BrS) and a diffuse cardiac conduction defect. Markers of increased risk for sudden cardiac death (SCD) in LoF SCN5A mutation carriers are ill defined. We hypothesized that late potentials and fragmented QRS would be more prevalent in SCN5A mutation carriers compared to SCN5A-negative BrS patients and evaluated risk markers for SCD in SCN5A mutation carriers., Methods: We included all SCN5A loss-of-function mutation carriers and SCN5A-negative BrS patients from our center. A combined arrhythmic endpoint was defined as appropriate ICD shock or SCD., Results: Late potentials were more prevalent in 79 SCN5A mutation carriers compared to 39 SCN5A-negative BrS patients (66% versus 44%, p = .021), while there was no difference in the prevalence of fragmented QRS. PR interval prolongation was the only parameter that predicted the presence of a SCN5A mutation in BrS (OR 1.08; p < .001). Four SCN5A mutation carriers, of whom three did not have a diagnostic type 1 ECG either spontaneously or after provocation with a sodium channel blocker, reached the combined arrhythmic endpoint during a follow-up of 44 ± 52 months resulting in an annual incidence rate of 1.37%., Conclusion: LP were more frequently observed in SCN5A mutation carriers, while fQRS was not. In SCN5A mutation carriers, the annual incidence rate of SCD was non-negligible, even in the absence of a spontaneous or induced type 1 ECG. Therefore, proper follow-up of SCN5A mutation carriers without Brugada syndrome phenotype is warranted., (© 2018 Wiley Periodicals, Inc.)

Pathogenic variants account for 4 to 41% of patients with intellectual disability (ID) or developmental delay (DD). In Sub-Saharan Africa, the prevalence of ID is thought to be higher, but data in Central Africa are limited to some case reports. In addition, clinical descriptions of some syndromes are not available for this population. This study aimed at providing an estimate for the fraction of ID/DD for which an underlying etiological genetic cause may be elucidated and provide insights into their clinical presentation in special institutions in a Central African country. A total of 127 patients (33 females and 94 males, mean age 10.03 ± 4.68 years), were recruited from six institutions across Kinshasa. A clinical diagnosis was achieved in 44 but molecular confirmation was achieved in 21 of the 22 patients with expected genetic defect (95% clinical sensitivity). Identified diseases included Down syndrome (15%), submicroscopic copy number variants (9%), aminoacylase deficiency (0.8%), Partington syndrome in one patient (0.8%) and his similarly affected brother, X-linked syndromic Mental Retardation type 33 (0.8%), and two conditions without clear underlying molecular genetic etiologies (Oculo-Auriculo-Vertebral and Amniotic Bands Sequence). We have shown that genetic etiologies, similar to those reported in Caucasian subjects, are a common etiologic cause of ID in African patients from Africa. We have confirmed the diagnostic utility of clinical characterization prior to genetic testing. Finally, our clinical descriptions provide insights into the presentation of these genetic diseases in African patients., (© 2018 Wiley Periodicals, Inc.)

Biallelic loss-of-function (LOF) mutations of the NCF4 gene, encoding the p40phox subunit of the phagocyte NADPH oxidase, have been described in only 1 patient. We report on 24 p40phox-deficient patients from 12 additional families in 8 countries. These patients display 8 different in-frame or out-of-frame mutations of NCF4 that are homozygous in 11 of the families and compound heterozygous in another. When overexpressed in NB4 neutrophil-like cells and EBV-transformed B cells in vitro, the mutant alleles were found to be LOF, with the exception of the p.R58C and c.120&#95;134del alleles, which were hypomorphic. Particle-induced NADPH oxidase activity was severely impaired in the patients' neutrophils, whereas PMA-induced dihydrorhodamine-1,2,3 (DHR) oxidation, which is widely used as a diagnostic test for chronic granulomatous disease (CGD), was normal or mildly impaired in the patients. Moreover, the NADPH oxidase activity of EBV-transformed B cells was also severely impaired, whereas that of mononuclear phagocytes was normal. Finally, the killing of Candida albicans and Aspergillus fumigatus hyphae by neutrophils was conserved in these patients, unlike in patients with CGD. The patients suffer from hyperinflammation and peripheral infections, but they do not have any of the invasive bacterial or fungal infections seen in CGD. Inherited p40phox deficiency underlies a distinctive condition, resembling a mild, atypical form of CGD.

Congenital or neonatal cardiomyopathies are commonly associated with a poor prognosis and have multiple etiologies. In two siblings, a male and female, we identified an undescribed type of lethal congenital restrictive cardiomyopathy affecting the right ventricle. We hypothesized a novel autosomal recessive condition. To identify the cause, we performed genetic, in vitro and in vivo studies. Genome-wide SNP typing and parametric linkage analysis was done in a recessive model to identify candidate regions. Exome sequencing analysis was done in unaffected and affected siblings. In the linkage regions, we selected candidate genes that harbor two rare variants with predicted functional effects in the patients and for which the unaffected sibling is either heterozygous or homozygous reference. We identified two compound heterozygous variants in KIF20A; a maternal missense variant (c.544C>T: p.R182W) and a paternal frameshift mutation (c.1905delT: p.S635Tfs*15). Functional studies confirmed that the R182W mutation creates an ATPase defective form of KIF20A which is not able to support efficient transport of Aurora B as part of the chromosomal passenger complex. Due to this, Aurora B remains trapped on chromatin in dividing cells and fails to translocate to the spindle midzone during cytokinesis. Translational blocking of KIF20A in a zebrafish model resulted in a cardiomyopathy phenotype. We identified a novel autosomal recessive congenital restrictive cardiomyopathy, caused by a near complete loss-of-function of KIF20A. This finding further illustrates the relationship of cytokinesis and congenital cardiomyopathy.

Left ventricular non-compaction (cardiomyopathy) (LVN(C)) is a rare hereditary cardiac condition, resulting from abnormal embryonic myocardial development. While it mostly occurs as an isolated condition, association with other cardiovascular manifestations such as Ebstein anomaly (EA) has been reported. This congenital heart defect is characterized by downward displacement of the tricuspid valve and leads to diminished ventricular size and function. In an autosomal dominant LVN(C) family consisting of five affected individuals, of which two also presented with EA and three with mitral valve insufficiency, we pursued the genetic disease cause using whole exome sequencing (WES). WES revealed a missense variant (p.Leu113Val) in TPM1 segregating with the LVN(C) phenotype. TPM1 encodes α-tropomyosin, which is involved in myocardial contraction, as well as in stabilization of non-muscle cytoskeletal actin filaments. So far, LVN(C)-EA has predominantly been linked to pathogenic variants in MYH7. However, one sporadic LVN(C)-EA case with a de novo TPM1 variant has recently been described. We here report the first LVN(C)-EA family segregating a pathogenic TPM1 variant, further establishing the association between EA predisposition and TPM1-related LVN(C). Consequently, we recommend genetic testing for both MYH7 and TPM1 in patients or families in which LVN(C)/non-compaction and EA coincide., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

In inherited primary arrhythmia syndromes (PAS) and cardiomyopathies (CMP), the yield of genetic testing varies between 20 and 75% in different diseases according to studies performed in the pre next-generation sequencing (NGS) era. It is unknown whether retesting historical negative samples with NGS techniques is worthwhile. Therefore, we assessed the value of NGS-based panel testing in previously genotype negative-phenotype positive probands. We selected 107 patients (47 PAS and 60 CMP) with a clear phenotype who remained genotype negative after genetic analysis of the main genes implicated in their specific phenotype. Targeted sequencing of the coding regions of 71 PAS- and CMP-related genes was performed. Variant interpretation and classification was done according to a cardiology-specific scoring algorithm ('Amsterdam criteria') and the ACMG-AMP criteria. Co-segregation analysis was performed when DNA and clinical data of family members were available. Finally, a genetic diagnosis could be established in 21 patients (20%), 5 PAS (11%) and 16 CMP (27%) patients, respectively. The increased detection rate was due to sequencing of novel genes in 52% of the cases and due to technical failures with the historical analysis in 48%. A total of 118 individuals were informed about their carrier state and either reassured or scheduled for proper follow-up. To conclude, genetic retesting in clinically overt PAS and CMP cases, who were genotype negative with older techniques, resulted in an additional genetic diagnosis in up to 20% of the cases. This clearly supports a policy for genetic retesting with NGS-based panels.

Introduction: Fetal akinesia deformation sequence (FADS) or arthrogryposis multiplex congenita (AMC) is characterized by clinical ambiguity and genetic heterogeneity, hampering genetic diagnosis via traditional sequencing methods. Next generation sequencing (NGS) of all known disease-causing genes offers an elegant solution to identify the genetic etiology of AMC/FADS in a diagnostic setting., Methods: An in-house developed disease-associated gene panel was conducted in two unrelated fetuses with FADS. First, a de novo analysis was performed on the entire disease-associated gene panel. If no pathogenic mutation was identified, analysis of variants retained in a specific subpanel with arthrogryposis/fetal akinesia-causing genes was performed., Results: In the first family, FADS relates to a homozygous c.484G > A (p.Glu162Lys) mutation in the gene RAPSN. The second case concerns a sporadic patient with brain anomalies and arthrogryposis due to a de novo hemizygous c.498C > T splice-site mutation in the pyruvate dehydrogenase-alpha 1 (PDHA1) gene., Discussion: NGS facilitated genetic diagnosis, and hence genetic counseling, for both families with AMC/FADS. Biallelic RAPSN mutations typically result in congenital myasthenia syndrome, or occasionally in FADS. This is the first report attributing the RAPSN mutation c.484G > A, identified in a homozygous state in patient 1, to FADS. The second patient represents the first case of AMC due to a PDHA1 mutation, advocating that pyruvate dehydrogenase deficiency should be considered in the differential diagnosis of fetal akinesia. This study illustrates the relevance of a disease-associated-gene panel as a diagnostic tool in pregnancies complicated by this genetically heterogeneous condition., (Copyright © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.)

Background: Gain-of-function mutations in transmembrane protein 173 (TMEM173) encoding stimulator of interferon genes (STING) underlie a recently described type I interferonopathy called STING-associated vasculopathy with onset in infancy (SAVI)., Objectives: We sought to define the molecular and cellular pathology relating to 3 individuals variably exhibiting the core features of the SAVI phenotype including systemic inflammation, destructive skin lesions, and interstitial lung disease., Methods: Genetic analysis, conformational studies, in vitro assays and ex vivo flow-cytometry were performed., Results: Molecular and in vitro data demonstrate that the pathology in these patients is due to amino acid substitutions at positions 206, 281, and 284 of the human STING protein. These mutations confer cGAMP-independent constitutive activation of type I interferon signaling through TBK1 (TANK-binding kinase), independent from the alternative STING pathway triggered by membrane fusion of enveloped RNA viruses. This constitutive activation was abrogated by ex vivo treatment with the janus kinase 1/2 inhibitor ruxolitinib., Conclusions: Structural analysis indicates that the 3 disease-associated mutations at positions 206, 281, and 284 of the STING protein define a novel cluster of amino acids with functional importance in the regulation of type I interferon signaling., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Background: Long QT syndrome (LQTS) is characterized by reduced penetrance and variable QT prolongation over time, resulting in an estimate of 25% carriers of a pathogenic mutation with a normal corrected QT (QTc) interval on the resting electrocardiogram (ECG)., Objective: The purpose of this study was to test the hypothesis that an individualized corrected QT interval derived from 24-hour Holter data more accurately predicts carriage of a pathogenic LQTS mutation than did QT derived from a standard 12-lead ECG and corrected using the Bazett formula (QTc interval)., Methods: Carriers of a pathogenic LQTS mutation and their genotype-negative family members who had both resting ECG and Holter recordings available were included. Automated and manual measurements of QTc were performed. QTi was derived from 24-hour Holter recordings and defined as the QT value at the intersection of an RR interval of 1000 ms, with the linear regression line fitted through QT-RR data points of each individual patient., Results: In total, 69 patients with LQTS (23 long QT type 1, 39 long QT type 2, and 7 long QT type 3) and 55 controls were selected. Demographic characteristics were comparable. A comparison of the receiver operating characteristic curves indicates that the test added diagnostic value compared to manual measurement (P = .02) or automated measurement (P = .005). The diagnostic accuracy of manually measured QTc using conventional cutoff criteria was 72%, while it was 92% using a sex-independent QTi cutoff of 445 ms. This was caused by a 39% increase in sensitivity without compromising the specificity., Conclusion: QTi derived from Holter recordings is superior to conventional QTc measured from a standard 12-lead ECG in predicting the mutation carrier state in families with LQTS., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

We present, on behalf of EuroGentest and the European Society of Human Genetics, guidelines for the evaluation and validation of next-generation sequencing (NGS) applications for the diagnosis of genetic disorders. The work was performed by a group of laboratory geneticists and bioinformaticians, and discussed with clinical geneticists, industry and patients' representatives, and other stakeholders in the field of human genetics. The statements that were written during the elaboration of the guidelines are presented here. The background document and full guidelines are available as supplementary material. They include many examples to assist the laboratories in the implementation of NGS and accreditation of this service. The work and ideas presented by others in guidelines that have emerged elsewhere in the course of the past few years were also considered and are acknowledged in the full text. Interestingly, a few new insights that have not been cited before have emerged during the preparation of the guidelines. The most important new feature is the presentation of a 'rating system' for NGS-based diagnostic tests. The guidelines and statements have been applauded by the genetic diagnostic community, and thus seem to be valuable for the harmonization and quality assurance of NGS diagnostics in Europe.

We present a new mutation in KCNH2 (c.2038delG) resulting in a frameshift and premature truncation of the IKr channel protein in a large LQTS family with several sudden death cases. This mutation was initially missed by mutation scanning with DHPLC due to allelic dropout and only retrieved after repeat genetic testing with targeted capture and massive parallel sequencing. There was full penetrance of this mutation, only if an individualized QT correction derived from 24-hour Holter data was used. This case again underscores the importance of repeat genetic testing in robust cases of LQTS that remained genotype negative with mutation scanning techniques.

Autosomal recessive IL-1R-associated kinase 4 (IRAK-4) deficiency is a rare cause of recurrent pyogenic infections with limited inflammatory responses. We describe an adult female patient with severe lung disease who was phenotypically diagnosed as suffering from autosomal dominant Hyper IgE syndrome (AD HIES) because of recurrent skin infections with Staphylococcus aureus, recurrent pneumonia and elevated serum IgE levels. In contrast to findings in AD HIES patients, no abnormalities were found in the Th17 and circulating follicular helper T cell subsets. A panel-based sequencing approach led to the identification of a homozygous IRAK4 stop mutation (c.877C > T, p.Gln293*).

To determine the diagnostic value of massive parallel sequencing of a panel of known cardiac genes in familial nonsyndromic congenital heart defects (CHD), targeted sequencing of the coding regions of 57 genes previously implicated in CHD was performed in 36 patients from 13 nonsyndromic CHD families with probable autosomal dominant inheritance. Following variant analysis and Sanger validation, we identified six potential disease causing variants in three genes (MYH6, NOTCH1, and TBX5), which may explain the defects in six families. Several problematic situations were encountered when performing genotype-phenotype correlations in the families to confirm the causality of these variants. In conclusion, by screening known CHD-associated genes in well-selected nonsyndromic CHD families and cautious variant interpretation, potential causative variants were identified in less than half of the families (6 out of 13; 46%). Variant interpretation remains a major challenge reflecting the complex genetic cause of CHD., (© 2015 Wiley Periodicals, Inc.)

MEIS2 has been associated with cleft palate and cardiac septal defects as well as varying degrees of intellectual disability. We present a female patient with a more severe phenotype compared to previous reported patients. She has multiple congenital malformations; cleft palate and congenital heart defect characterized by septal defects and aortic coarctation. She has severe feeding problems, facial dysmorphism, severely delayed gross motor and verbal development, and autism spectrum disorder. Facial dysmorphism consisting of bitemporal narrowing, arched and laterally extended eyebrows, mild upslanting palpebral fissures, deep-set eyes, a tented upper lip, thin upper vermilion, full lower vermilion, broad first ray of hands and feet, a gap between the first and second toes, and syndactyly of toe II-III. Exome sequencing revealed a non-frameshift deletion (c.998&#95;1000del:p.Arg333del) of three base pairs in the MEIS2 homeodomain. The more severe phenotype is most probably due to dominant-negative mechanisms. This is the first report showing a de novo small intragenic mutation in MEIS2 and further confirms the important role of this gene in normal development., (© 2015 Wiley Periodicals, Inc.)

Background: Congenital anomalies of kidneys and urinary tract (CAKUT) are the most predominant developmental disorders comprising ∼20-30% of all anomalies identified in the prenatal period. Mutations in hepatocyte nuclear factor 1-beta (HNF-1β) involved in the development of kidneys, liver, pancreas and urogenital tract are currently the most frequent monogenetic cause of CAKUT found in 10-30% of patients depending on screening policy and study design. We aimed to validate criteria for analysis of HNF1B in a prospective cohort of paediatric and adult CAKUT patients., Methods: We included CAKUT patients diagnosed in our paediatric and adult nephrology departments from January 2010 until April 2013 based on predefined screening criteria. Subjects presenting with at least one major renal criterion or one minor renal criterion combined with one or more extra-renal criteria in the personal history or a familial history of renal or extra-renal manifestations were considered eligible., Results: We prospectively screened 205 patients and detected HNF1B mutations in 10% [n = 20, 12 children, median age 4.2 (range 0-13.1) years and 8 adults, median age 34.8 (range 16.6-62) years]. We observed that bilateral renal anomaly, renal cysts from unknown origin, a combination of two major renal anomalies and hypomagnesaemia were predictive for finding HNF1B mutations (P < 0.001; P < 0.001; P = 0.004; P = 0.008, respectively)., Conclusions: We demonstrated that HNF1B mutations are responsible for ∼10% of CAKUT cases, both in children and in adults. Based on our results we propose adapted criteria for HNF1B analysis to reduce the screening costs without missing affected patients. These criteria should be reaffirmed in a larger validation cohort., (© The Author 2014. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.)

Background: Two siblings from consanguineous parents of Turkish descent presented with isolated dilated cardiomyopathy, leading to early death in infancy. The diagnosis of mitogenic cardiomyopathy was made histologically., Methods and Results: Linkage analysis combined with exome sequencing identified a homozygous deleterious mutation in the ALMS1 gene as the cause of this phenotype., Conclusions: Alström syndrome is characterized by a typically transient dilating cardiomyopathy in infancy, suggesting that mitogenic cardiomyopathy represents the extreme phenotype, resulting in demise before the other clinical symptoms become evident. This observation further illustrates the role of ALMS1 and cell cycle regulation., (Copyright © 2014. Published by Elsevier Masson SAS.)

Apert syndrome (OMIM 101200) is a rare genetic condition characterized by craniosynostosis and syndactyly of hands and feet with clinical variability. Two single nucleotides mutations in the linker region between the immunoglobulin-like domains II and IIIa of the ectodomainin the Fibroblast Growth Factor Receptor 2 gene (FGFR2, OMIM 176943) are responsible of the vast majority of cases: c.755C > G; p.Ser252Trp (65%) and c.758C > G; p.Pro253Arg (34%. Three exceptional cases carry multiple substitutions of adjacent nucleotides in the linker region. Here we present a Congolese male patient and his mother, both affected with Apert syndrome of variable severity, carrying a previously undescribed heterozygous mutation of three consecutive nucleotides (c.756&#95;758delGCCinsCTT) in the IgII-IgIIIa linker region. This is the fourth live-born patient to carry a multiple nucleotide substitution in the linker region and is the second alternative amino acid substitutions of the Pro253. Remarkably, this novel mutation was detected in the first Central African patient ever to be tested molecularly for the Apert syndrome. To discriminate between a hitherto unreported mutation and an ethnic specific polymorphism, we tested 105 Congolese controls, and no variation was detected., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Objectives: The Z allele (Glu342Lys) in α1-antitrypsin (AAT) deficiency is a combined deficiency and dysfunctional allele. Carrying one Z allele induces a risk of a more aggressive evolution in patients with a chronic liver disease. As most of the carriers of Z allele do not have overt liver disease, it is likely that Z allele-containing livers have been used previously for liver transplantation. We analyzed the incidence, epidemiology, and clinical features of AAT accumulation in the hepatocytes after liver transplantation., Methods: Follow-up biopsies of liver transplant recipients were analyzed with periodic acid Schiff staining until 2006 (n=486); from 2006 on (n=303), all biopsies were stained with a specific monoclonal antibody against mutated AATZ protein. Genotyping of both recipient and donor was performed in the case of positive staining., Results: Of 789 liver transplantation patients, six patients (0.8%) showed mutated AATZ accumulation in the transplanted liver. Mutation analysis confirmed the presence of the Z allele in all donor organs including one transplanted organ with the SZ phenotype. There was a clear concordance between the isoelectrical focusing of the recipient AAT after transplantation and the genotype of the donor., Conclusion: Presumed healthy donor organs containing the Z allele were used for transplantation in 0.8% of cases in our series. As the presence of a Z allele is an independent risk factor of aggravation of chronic liver disease, AATZ accumulation in biopsies after liver transplantation should be actively looked for.

Shwachman-Diamond syndrome (SDS) is an autosomal recessive disorder characterised by skeletal dysplasia, exocrine pancreatic insufficiency and bone marrow failure. Various other conditions, such as hepatopathy and failure to thrive have been associated with SDS. A retrospective study was conducted to describe mutations, clinical features, and the immunological profile of 11 Belgian patients with genetically confirmed diagnosis of SDS. This study confirms the existing understanding of the classical features of SDS although the typical triad was present in only six out of nine fully studied patients. The following important observations are made in this cohort. Four out of eleven patients were misdiagnosed as having Asphyxiating Thoracic Dystrophy (Jeune syndrome) because of severe thoracic dystrophy. Another two patients presented with unexplained episodes of symptomatic hypoglycaemia. The immunological phenotype was heterogeneous although laboratory abnormalities were noticed in eight out of ten patients assessed. Three patients experienced a life threatening viral infection (respiratory syncytial virus, cytomegalovirus (CMV) and rotavirus). In one patient, CMV infection caused an episode of haemophagocytic lymphohistiocytosis. One patient has bronchiectasis at the age of 3 years due to recurrent respiratory tract infections. These findings strengthen the suspicion of an abnormal immune system in SDS. Liver anomalies, usually described as benign and transitory in SDS patients, were severe in two patients of the cohort. One patient developed hepatopulmonary syndrome. The findings in this national cohort of SDS patients could contribute to the prevention of misdiagnosis in the future and enable more rapid recognition of certain severe complications.

Mutations in COL4A1 have been identified in families with hereditary small vessel disease of the brain presumably due to a dominant-negative mechanism. Here, we report on two novel mutations in COL4A1 in two families with porencephaly, intracerebral hemorrhage and severe white matter disease caused by haploinsufficiency. Two families with various clinical presentations of cerebral microangiopathy and autosomal dominant inheritance were examined. Clinical, neuroradiological and genetic investigations were performed. Electron microscopy of the skin was also performed. In one of the families, sequence analysis revealed a one base deletion, c.2085del, leading to a frameshift and a premature stopcodon, p.(Gly696fs). In the other family, a splice site mutation was identified, c.2194-1G>A, which most likely leads to skipping of an exon with a frameshift and premature termination as a result. In fibroblasts of affected individuals from both the families, nonsense-mediated decay (NMD) of the mutant COL4A1 messenger RNAs (mRNAs) and a clear reduction of COL4A1 protein expression were demonstrated, indicating haploinsufficiency of COL4A1. Moreover, thickening of the capillary basement membrane in the skin was documented, similar to reports in patients with COL4A1 missense mutations. These findings suggest haploinsufficiency, a different mechanism from the commonly assumed dominant-negative effect, for COL4A1 mutations as a cause of (antenatal) intracerebral hemorrhage and white matter disease.

The validation and verification of laboratory methods and procedures before their use in clinical testing is essential for providing a safe and useful service to clinicians and patients. This paper outlines the principles of validation and verification in the context of clinical human molecular genetic testing. We describe implementation processes, types of tests and their key validation components, and suggest some relevant statistical approaches that can be used by individual laboratories to ensure that tests are conducted to defined standards.