Publications by authors named "Arjan C Houweling"

35 Publications

Loss of FLCN-FNIP1/2 induces a non-canonical interferon response in human renal tubular epithelial cells.

Elife 2021 Jan 18;10. Epub 2021 Jan 18.

Amsterdam UMC, location VUmc, Vrije Universiteit Amsterdam, Clinical Genetics, Cancer Center Amsterdam, Amsterdam, Netherlands.

Germline mutations in the Folliculin () tumor suppressor gene cause Birt-Hogg-Dubé (BHD) syndrome, a rare autosomal dominant disorder predisposing carriers to kidney tumors. is a conserved, essential gene linked to diverse cellular processes but the mechanism by which prevents kidney cancer remains unknown. Here, we show that disrupting in human renal tubular epithelial cells (RPTEC/TERT1) activates TFE3, upregulating expression of its E-box targets, including RRAGD and GPNMB, without modifying mTORC1 activity. Surprisingly, the absence of FLCN or its binding partners FNIP1/FNIP2 induces interferon response genes independently of interferon. Mechanistically, FLCN loss promotes STAT2 recruitment to chromatin and slows cellular proliferation. Our integrated analysis identifies STAT1/2 signaling as a novel target of FLCN in renal cells and BHD tumors. STAT1/2 activation appears to counterbalance TFE3-directed hyper-proliferation and may influence immune responses. These findings shed light on unique roles of FLCN in human renal tumorigenesis and pinpoint candidate prognostic biomarkers.
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http://dx.doi.org/10.7554/eLife.61630DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7899648PMC
January 2021

Genetic Evaluation in a Cohort of 126 Dutch Pulmonary Arterial Hypertension Patients.

Genes (Basel) 2020 Oct 13;11(10). Epub 2020 Oct 13.

Department of Clinical Genetics, Amsterdam UMC (location VUmc), 1081HV Amsterdam, The Netherlands.

Pulmonary arterial hypertension (PAH) is a severe, life-threatening disease, and in some cases is caused by genetic defects. This study sought to assess the diagnostic yield of genetic testing in a Dutch cohort of 126 PAH patients. Historically, genetic testing in the Netherlands consisted of the analysis of BMPR2 and SMAD9. These genes were analyzed in 70 of the 126 patients. A (likely) pathogenic (LP/P) variant was detected in 22 (31%) of them. After the identification of additional PAH associated genes, a next generation sequencing (NGS) panel consisting of 19 genes was developed in 2018. Additional genetic testing was offered to the 48 and negative patients, out of which 28 opted for NGS analysis. In addition, this gene panel was analyzed in 56 newly identified idiopathic (IPAH) or pulmonary veno occlusive disease (PVOD) patients. In these 84 patients, NGS panel testing revealed LP/P variants in BMPR2 ( = 4), GDF2 ( = 2), EIF2AK4 ( = 1), and TBX4 ( = 3). Furthermore, 134 relatives of 32 probands with a LP/P variant were tested, yielding 41 carriers. NGS panel screening offered to IPAH/PVOD patients led to the identification of LP/P variants in GDF2, EIF2AK4, and TBX4 in six additional patients. The identification of LP/P variants in patients allows for screening of at-risk relatives, enabling the early identification of PAH.
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http://dx.doi.org/10.3390/genes11101191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602048PMC
October 2020

Phenotypic spectrum of TGFB3 disease-causing variants in a Dutch-French cohort and first report of a homozygous patient.

Clin Genet 2020 05 16;97(5):723-730. Epub 2020 Jan 16.

Département de Génétique, Assistance Publique-Hôpitaux de Paris, Hôpital Bichat, Paris, France.

Disease-causing variants in TGFB3 cause an autosomal dominant connective tissue disorder which is hard to phenotypically delineate because of the small number of identified cases. The purpose of this retrospective cross-sectional multicenter study is to elucidate the genotype and phenotype in an international cohort of TGFB3 patients. Eleven (eight novel) TGFB3 disease-causing variants were identified in 32 patients (17 families). Aortic root dilatation and mitral valve disease represented the most common cardiovascular findings, reported in 29% and 32% of patients, respectively. Dissection involving distal aortic segments occurred in two patients at age 50 and 52 years. A high frequency of systemic features (65% high-arched palate, 63% arachnodactyly, 57% pectus deformity, 52% joint hypermobility) was observed. In familial cases, incomplete penetrance and variable clinical expressivity were noted. Our cohort included the first described homozygous patient, who presented with a more severe phenotype compared to her heterozygous relatives. In conclusion, TGFB3 variants were associated with a high percentage of systemic features and aortic disease (dilatation/dissection) in 35% of patients. No deaths occurred from cardiovascular events or pregnancy-related complications. Nevertheless, homozygosity may be driving a more severe phenotype.
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http://dx.doi.org/10.1111/cge.13700DOI Listing
May 2020

No evidence for increased prevalence of colorectal carcinoma in 399 Dutch patients with Birt-Hogg-Dubé syndrome.

Br J Cancer 2020 02 20;122(4):590-594. Epub 2019 Dec 20.

Amsterdam UMC, Vrije Universiteit Amsterdam, Clinical Genetics, De Boelelaan, 1117, Amsterdam, Netherlands.

Background: Previously, it has been suggested that colorectal polyps and carcinomas might be associated with Birt-Hogg-Dubé syndrome. We aimed to compare the occurrence of colorectal neoplasms between Dutch patients with Birt-Hogg-Dubé syndrome and their relatives without Birt-Hogg-Dubé syndrome.

Methods: In all, 399 patients with a pathogenic FLCN mutation and 382 relatives without the familial FLCN mutation were included. Anonymous data on colon and rectum pathology was provided by PALGA: the Dutch Pathology Registry.

Results: No significant difference in the percentage of individuals with a history of colorectal carcinoma was found between the two groups (3.6% vs 2.6%, p = 0.54). There was also no significant difference between the age at diagnosis, diameter, differentiation and location of the colorectal carcinomas. Significantly more individuals with Birt-Hogg-Dubé syndrome underwent removal of colorectal polyps (12.2% vs 6.3%, p = 0.005). However, there was no significant difference between the number of polyps per person, the histology, grade of dysplasia and location of the polyps.

Conclusion: Our data do not provide evidence for an increased risk for colorectal carcinoma in Birt-Hogg-Dubé syndrome, arguing against the need for colorectal surveillance. The difference in polyps might be due to a bias caused by a higher number of colonoscopies in patients with Birt-Hogg-Dubé syndrome.
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http://dx.doi.org/10.1038/s41416-019-0693-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7028712PMC
February 2020

Characterization of Mutations and Levels of BMP9 and BMP10 in Pulmonary Arterial Hypertension.

Am J Respir Crit Care Med 2020 03;201(5):575-585

National Heart and Lung Institute, Imperial College London, London, United Kingdom.

Recently, rare heterozygous mutations in were identified in patients with pulmonary arterial hypertension (PAH). encodes the circulating BMP (bone morphogenetic protein) type 9, which is a ligand for the BMP2 receptor. Here we determined the functional impact of mutations and characterized plasma BMP9 and BMP10 levels in patients with idiopathic PAH. Missense BMP9 mutant proteins were expressed and the impact on BMP9 protein processing and secretion, endothelial signaling, and functional activity was assessed. Plasma BMP9 and BMP10 levels and activity were assayed in patients with PAH with variants and in control subjects. Levels were also measured in a larger cohort of control subjects ( = 120) and patients with idiopathic PAH ( = 260). We identified a novel rare variation at the and loci, including copy number variation. , BMP9 missense proteins demonstrated impaired cellular processing and secretion. Patients with PAH who carried these mutations exhibited reduced plasma levels of BMP9 and reduced BMP activity. Unexpectedly, plasma BMP10 levels were also markedly reduced in these individuals. Although overall BMP9 and BMP10 levels did not differ between patients with PAH and control subjects, BMP10 levels were lower in PAH females. A subset of patients with PAH had markedly reduced plasma levels of BMP9 and BMP10 in the absence of mutations. Our findings demonstrate that mutations result in BMP9 loss of function and are likely causal. These mutations lead to reduced circulating levels of both BMP9 and BMP10. These findings support therapeutic strategies to enhance BMP9 or BMP10 signaling in PAH.
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http://dx.doi.org/10.1164/rccm.201906-1141OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7047445PMC
March 2020

Loss-of-function variants in myocardin cause congenital megabladder in humans and mice.

J Clin Invest 2019 12;129(12):5374-5380

Department of Experimental Cardiology, Amsterdam UMC, Amsterdam, Netherlands.

Myocardin (MYOCD) is the founding member of a class of transcriptional coactivators that bind the serum-response factor to activate gene expression programs critical in smooth muscle (SM) and cardiac muscle development. Insights into the molecular functions of MYOCD have been obtained from cell culture studies, and to date, knowledge about in vivo roles of MYOCD comes exclusively from experimental animals. Here, we defined an often lethal congenital human disease associated with inheritance of pathogenic MYOCD variants. This disease manifested as a massively dilated urinary bladder, or megabladder, with disrupted SM in its wall. We provided evidence that monoallelic loss-of-function variants in MYOCD caused congenital megabladder in males only, whereas biallelic variants were associated with disease in both sexes, with a phenotype additionally involving the cardiovascular system. These results were supported by cosegregation of MYOCD variants with the phenotype in 4 unrelated families by in vitro transactivation studies in which pathogenic variants resulted in abrogated SM gene expression and by the finding of megabladder in 2 distinct mouse models with reduced Myocd activity. In conclusion, we have demonstrated that variants in MYOCD result in human disease, and the collective findings highlight a vital role for MYOCD in mammalian organogenesis.
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http://dx.doi.org/10.1172/JCI128545DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6877301PMC
December 2019

Mortality Risk Associated With Truncating Founder Mutations in Titin.

Circ Genom Precis Med 2019 05;12(5):e002436

Department of Genetics (M.J., A.F.B., A.S.U., H.K.P.v.A., E.A.M.H., D.D.), University Medical Center Utrecht, Utrecht University, the Netherlands.

Background Truncating titin variants (TTNtv) are the most prevalent genetic cause of dilated cardiomyopathy, found in ≤25% of familial cases. Moreover, TTNtv associated with dilated cardiomyopathy are estimated to be present in 0.5% of the general population. The prognosis of asymptomatic carriers of TTNtv is poorly understood because TTNtv are associated with a highly variable phenotype. We aim to assess the natural history and clinical relevance of TTNtv by analyzing standardized mortality ratios (SMR) in multigenerational pedigrees and in close relatives of present-day patients. Methods Haplotype and genealogical analyses were performed on 3 recurrent TTNtv. Subsequently, the family tree mortality ratio method was used to compare all-cause mortality of subjects at an a priori 50% risk of carrying TTNtv to the general Dutch population. SMRs were stratified for sex, age, and calendar period. Subgroups were compared with Poisson regression. Similarly, SMRs were calculated in parents of 128 present-day dilated cardiomyopathy probands with TTNtv using the reverse parent-offspring method. Results The TTNtv were established as founder mutations and traced to 18th century ancestors. In 20 522 person-years, overall mortality was not significantly increased (SMR, 1.06; 95% CI, 0.95-1.18; P=0.162). However, mortality was significantly increased in subjects living after 1965 (SMR, 1.27; 95% CI, 1.04-1.53; P=0.009) and aged ≥60 years (SMR, 1.17; 95% CI, 1.01-1.35; P=0.02). The reverse parent-offspring analysis showed overall excess mortality (SMR, 1.26; 95% CI, 1.07-1.48; P=0.003), driven by subjects aged ≥60 years. Conclusions The natural history of the analyzed TTNtv shows a relatively mild disease course with significant excess mortality in elderly patients. With increasing life expectancy, TTNtv-associated morbidity and mortality will likely become more prevalent.
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http://dx.doi.org/10.1161/CIRCGEN.118.002436DOI Listing
May 2019

Renal imaging in 199 Dutch patients with Birt-Hogg-Dubé syndrome: Screening compliance and outcome.

PLoS One 2019 7;14(3):e0212952. Epub 2019 Mar 7.

Department of Urology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, the Netherlands.

Birt-Hogg-Dubé syndrome is associated with an increased risk for renal cell carcinoma. Surveillance is recommended, but the optimal imaging method and screening interval remain to be defined. The main aim of our study was to evaluate the outcomes of RCC surveillance to get insight in the safety of annual US in these patients. Surveillance data and medical records of 199 patients with Birt-Hogg-Dubé syndrome were collected retrospectively using medical files and a questionnaire. These patients were diagnosed in two Dutch hospitals and data were collected until June 2014. A first screening for renal cell carcinoma was performed in 172/199 patients (86%). Follow-up data were available from 121 patients. The mean follow-up period per patient was 4.2 years. Of the patients known to be under surveillance, 83% was screened at least annually and 94% at least every two years. Thirty-eight renal cell carcinomas had occurred in 23 patients. The mean age at diagnosis of the first tumour was 51. Eighteen tumours were visualized by ultrasound. Nine small tumours (7-27 mm) were visible on MRI or CT and not detected using ultrasound. Our data indicate that compliance to renal screening is relatively high. Furthermore, ultrasound might be a sensitive, cheap and widely available alternative for MRI or part of the MRIs for detecting clinically relevant renal tumours in BHD patients,but the limitations should be considered carefully. Data from larger cohorts are necessary to confirm these observations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212952PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6405080PMC
December 2019

Genetic determinants of risk in pulmonary arterial hypertension: international genome-wide association studies and meta-analysis.

Lancet Respir Med 2019 03 5;7(3):227-238. Epub 2018 Dec 5.

Medstar Health, Washington, DC, USA.

Background: Rare genetic variants cause pulmonary arterial hypertension, but the contribution of common genetic variation to disease risk and natural history is poorly characterised. We tested for genome-wide association for pulmonary arterial hypertension in large international cohorts and assessed the contribution of associated regions to outcomes.

Methods: We did two separate genome-wide association studies (GWAS) and a meta-analysis of pulmonary arterial hypertension. These GWAS used data from four international case-control studies across 11 744 individuals with European ancestry (including 2085 patients). One GWAS used genotypes from 5895 whole-genome sequences and the other GWAS used genotyping array data from an additional 5849 individuals. Cross-validation of loci reaching genome-wide significance was sought by meta-analysis. Conditional analysis corrected for the most significant variants at each locus was used to resolve signals for multiple associations. We functionally annotated associated variants and tested associations with duration of survival. All-cause mortality was the primary endpoint in survival analyses.

Findings: A locus near SOX17 (rs10103692, odds ratio 1·80 [95% CI 1·55-2·08], p=5·13 × 10) and a second locus in HLA-DPA1 and HLA-DPB1 (collectively referred to as HLA-DPA1/DPB1 here; rs2856830, 1·56 [1·42-1·71], p=7·65 × 10) within the class II MHC region were associated with pulmonary arterial hypertension. The SOX17 locus had two independent signals associated with pulmonary arterial hypertension (rs13266183, 1·36 [1·25-1·48], p=1·69 × 10; and rs10103692). Functional and epigenomic data indicate that the risk variants near SOX17 alter gene regulation via an enhancer active in endothelial cells. Pulmonary arterial hypertension risk variants determined haplotype-specific enhancer activity, and CRISPR-mediated inhibition of the enhancer reduced SOX17 expression. The HLA-DPA1/DPB1 rs2856830 genotype was strongly associated with survival. Median survival from diagnosis in patients with pulmonary arterial hypertension with the C/C homozygous genotype was double (13·50 years [95% CI 12·07 to >13·50]) that of those with the T/T genotype (6·97 years [6·02-8·05]), despite similar baseline disease severity.

Interpretation: This is the first study to report that common genetic variation at loci in an enhancer near SOX17 and in HLA-DPA1/DPB1 is associated with pulmonary arterial hypertension. Impairment of SOX17 function might be more common in pulmonary arterial hypertension than suggested by rare mutations in SOX17. Further studies are needed to confirm the association between HLA typing or rs2856830 genotyping and survival, and to determine whether HLA typing or rs2856830 genotyping improves risk stratification in clinical practice or trials.

Funding: UK NIHR, BHF, UK MRC, Dinosaur Trust, NIH/NHLBI, ERS, EMBO, Wellcome Trust, EU, AHA, ACClinPharm, Netherlands CVRI, Dutch Heart Foundation, Dutch Federation of UMC, Netherlands OHRD and RNAS, German DFG, German BMBF, APH Paris, INSERM, Université Paris-Sud, and French ANR.
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http://dx.doi.org/10.1016/S2213-2600(18)30409-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391516PMC
March 2019

Autosomal dominant Marfan syndrome caused by a previously reported recessive FBN1 variant.

Mol Genet Genomic Med 2019 02 28;7(2):e00518. Epub 2018 Nov 28.

Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Background: Pathogenic variants in FBN1 cause autosomal dominant Marfan syndrome but can also be found in patients presenting with apparently isolated features of Marfan syndrome. Moreover, several families with autosomal recessive Marfan syndrome caused by pathogenic variants in FBN1 have been described. The aim of this report was to underline the clinical variability that can be associated with the pathogenic variant c.1453C>T, p.(Arg485Cys) in FBN1.

Methods: We provide the clinical details of two autosomal dominant families with this specific FBN1 variant, which was previously associated with autosomal recessive Marfan syndrome.

Results: Clinical data of 14 individuals carrying this variant from these two families were collected retrospectively. In both families, the diagnosis of autosomal dominant Marfan syndrome was established based on the characteristics of the variant and the phenotype which includes aortic aneurysms and dissections. Of interest, in one of the families, multiple relatives were diagnosed with early onset abdominal aortic aneurysms.

Conclusion: In conclusion, FBN1 variant c.1453C>T, p.(Arg485Cys) is a pathogenic variant that can cause autosomal dominant Marfan syndrome characterized by a high degree of clinical variability and apparently isolated early onset familial abdominal aortic aneurysms.
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http://dx.doi.org/10.1002/mgg3.518DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6393656PMC
February 2019

Loss-of-Function ABCC8 Mutations in Pulmonary Arterial Hypertension.

Circ Genom Precis Med 2018 10;11(10):e002087

AP-HP (Assistance Publique - Hôpitaux de Paris), Centre de référence de l'hypertension pulmonaire sévère, INSERM UMR_S 999, Hôpital Bicêtre, Université Paris-Sud, Université Paris-Saclay, Le Kremlin-Bicêtre, France (B.G., M.H., C.G., D.M.).

Background: In pulmonary arterial hypertension (PAH), pathological changes in pulmonary arterioles progressively raise pulmonary artery pressure and increase pulmonary vascular resistance, leading to right heart failure and high mortality rates. Recently, the first potassium channelopathy in PAH, because of mutations in KCNK3, was identified as a genetic cause and pharmacological target.

Methods: Exome sequencing was performed to identify novel genes in a cohort of 99 pediatric and 134 adult-onset group I PAH patients. Novel rare variants in the gene identified were independently identified in a cohort of 680 adult-onset patients. Variants were expressed in COS cells and function assessed by patch-clamp and rubidium flux analysis.

Results: We identified a de novo novel heterozygous predicted deleterious missense variant c.G2873A (p.R958H) in ABCC8 in a child with idiopathic PAH. We then evaluated all individuals in the original and a second cohort for rare or novel variants in ABCC8 and identified 11 additional heterozygous predicted damaging ABCC8 variants. ABCC8 encodes SUR1 (sulfonylurea receptor 1)-a regulatory subunit of the ATP-sensitive potassium channel. We observed loss of ATP-sensitive potassium channel function for all ABCC8 variants evaluated and pharmacological rescue of all channel currents in vitro by the SUR1 activator, diazoxide.

Conclusions: Novel and rare missense variants in ABCC8 are associated with PAH. Identified ABCC8 mutations decreased ATP-sensitive potassium channel function, which was pharmacologically recovered.
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http://dx.doi.org/10.1161/CIRCGEN.118.002087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6206877PMC
October 2018

Results of next-generation sequencing gene panel diagnostics including copy-number variation analysis in 810 patients suspected of heritable thoracic aortic disorders.

Hum Mutat 2018 09 12;39(9):1173-1192. Epub 2018 Jul 12.

Department of Clinical Genetics, VU University Medical Center, Amsterdam, the Netherlands.

Simultaneous analysis of multiple genes using next-generation sequencing (NGS) technology has become widely available. Copy-number variations (CNVs) in disease-associated genes have emerged as a cause for several hereditary disorders. CNVs are, however, not routinely detected using NGS analysis. The aim of this study was to assess the diagnostic yield and the prevalence of CNVs using our panel of Hereditary Thoracic Aortic Disease (H-TAD)-associated genes. Eight hundred ten patients suspected of H-TAD were analyzed by targeted NGS analysis of 21 H-TAD associated genes. In addition, the eXome hidden Markov model (XHMM; an algorithm to identify CNVs in targeted NGS data) was used to detect CNVs in these genes. A pathogenic or likely pathogenic variant was found in 66 of 810 patients (8.1%). Of these 66 pathogenic or likely pathogenic variants, six (9.1%) were CNVs not detectable by routine NGS analysis. These CNVs were four intragenic (multi-)exon deletions in MYLK, TGFB2, SMAD3, and PRKG1, respectively. In addition, a large duplication including NOTCH1 and a large deletion encompassing SCARF2 were detected. As confirmed by additional analyses, both CNVs indicated larger chromosomal abnormalities, which could explain the phenotype in both patients. Given the clinical relevance of the identification of a genetic cause, CNV analysis using a method such as XHMM should be incorporated into the clinical diagnostic care for H-TAD patients.
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http://dx.doi.org/10.1002/humu.23565DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6175145PMC
September 2018

Identification of rare sequence variation underlying heritable pulmonary arterial hypertension.

Nat Commun 2018 04 12;9(1):1416. Epub 2018 Apr 12.

National Heart & Lung Institute, Imperial College London, London, SW3 6LY, United Kingdom.

Pulmonary arterial hypertension (PAH) is a rare disorder with a poor prognosis. Deleterious variation within components of the transforming growth factor-β pathway, particularly the bone morphogenetic protein type 2 receptor (BMPR2), underlies most heritable forms of PAH. To identify the missing heritability we perform whole-genome sequencing in 1038 PAH index cases and 6385 PAH-negative control subjects. Case-control analyses reveal significant overrepresentation of rare variants in ATP13A3, AQP1 and SOX17, and provide independent validation of a critical role for GDF2 in PAH. We demonstrate familial segregation of mutations in SOX17 and AQP1 with PAH. Mutations in GDF2, encoding a BMPR2 ligand, lead to reduced secretion from transfected cells. In addition, we identify pathogenic mutations in the majority of previously reported PAH genes, and provide evidence for further putative genes. Taken together these findings contribute new insights into the molecular basis of PAH and indicate unexplored pathways for therapeutic intervention.
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http://dx.doi.org/10.1038/s41467-018-03672-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5897357PMC
April 2018

Iris Flocculi and Type B Aortic Dissection.

Ophthalmology 2017 11;124(11):1711

Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands.

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http://dx.doi.org/10.1016/j.ophtha.2017.05.011DOI Listing
November 2017

The diagnostic yield of whole-exome sequencing targeting a gene panel for hearing impairment in The Netherlands.

Eur J Hum Genet 2017 02 21;25(3):308-314. Epub 2016 Dec 21.

The Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands.

Hearing impairment (HI) is genetically heterogeneous which hampers genetic counseling and molecular diagnosis. Testing of several single HI-related genes is laborious and expensive. In this study, we evaluate the diagnostic utility of whole-exome sequencing (WES) targeting a panel of HI-related genes. Two hundred index patients, mostly of Dutch origin, with presumed hereditary HI underwent WES followed by targeted analysis of an HI gene panel of 120 genes. We found causative variants underlying the HI in 67 of 200 patients (33.5%). Eight of these patients have a large homozygous deletion involving STRC, OTOA or USH2A, which could only be identified by copy number variation detection. Variants of uncertain significance were found in 10 patients (5.0%). In the remaining 123 cases, no potentially causative variants were detected (61.5%). In our patient cohort, causative variants in GJB2, USH2A, MYO15A and STRC, and in MYO6 were the leading causes for autosomal recessive and dominant HI, respectively. Segregation analysis and functional analyses of variants of uncertain significance will probably further increase the diagnostic yield of WES.
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http://dx.doi.org/10.1038/ejhg.2016.182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5315517PMC
February 2017

Two cases of RIT1 associated Noonan syndrome: Further delineation of the clinical phenotype and review of the literature.

Am J Med Genet A 2016 07 25;170(7):1874-80. Epub 2016 Apr 25.

Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands.

Mutations in RIT1, involved in the RAS-MAPK pathway, have recently been identified as a cause for Noonan syndrome. We present two patients with Noonan syndrome caused by a RIT1 mutation with novel phenotypic manifestations, severe bilateral lower limb lymphedema starting during puberty, and fetal hydrops resulting in intrauterine fetal death, respectively. Including our patients, a total of 52 patients have been reported with Noonan syndrome caused by a RIT1 mutation. Our report contributes to the delineation of the phenotype associated with RIT1 mutations and underlines that lymphatic involvement is part of this spectrum. In addition, we provide an overview of the currently described Noonan syndrome patients with RIT1 mutations in literature. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37657DOI Listing
July 2016

A case of pulmonary alveolar microlithiasis associated with a homozygous 195 kb deletion encompassing the entire SLC34A2 gene.

Clin Case Rep 2016 Apr 11;4(4):412-5. Epub 2016 Mar 11.

Department of clinical genetics VU University Medical Center Amsterdam The Netherlands.

With around 500 cases published worldwide, pulmonary alveolar microlithiasis is a rare disorder with an autosomal recessive pattern of inheritance. We show for the first time that homozygous deletions encompassing the entire SCL34A2 can be associated with this rare genetic pulmonary disease.
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http://dx.doi.org/10.1002/ccr3.532DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4831397PMC
April 2016

Bone Morphogenetic Protein Receptor Type 2 Mutation in Pulmonary Arterial Hypertension: A View on the Right Ventricle.

Circulation 2016 May 16;133(18):1747-60. Epub 2016 Mar 16.

From Department of Pulmonology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands (C.E.E.V.D.B., C.M.H., P.T., O.A.S., N.R., A.V.N., H.J.B., F.S.d.M.); Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands (C.M.H., N.R., F.P.H., J.V.D.V., F.S.d.M.); Univ. Paris-Sud, Le Kremlin-Bicêtre, France (P.D., B.G., .M.H.); AP-HP, Service de Pneumologie, Centre de Référence de l'Hypertension Pulmonaire Sévère, DHU Thorax Innovation, Hôpital Bicêtre, Le Kremlin-Bicêtre, France (P.D., B.G., M.H.); INSERM999, LabEx LERMIT, Centre Chirurgical Marie Lannelongue, Le Plessis Robinson, France (P.D., B.G., M.H.); Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands (A.C.H.); Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands (J.T.M.); Department of Thoracic and Vascular Surgery and Heart-Lung Transplantation, Hôpital Marie-Lannelongue, Le Plessis Robinson, Paris-Sud University, France (O.M.); Department of Cardiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands (M.L.H.); and Department of Molecular Cell Biology, Laboratory of Experimental Cardiology, Leiden University Medical Center, Leiden, The Netherlands (M.-J.G.).

Background: The effect of a mutation in the bone morphogenetic protein receptor 2 (BMPR2) gene on right ventricular (RV) pressure overload in patients with pulmonary arterial hypertension is unknown. Therefore, we investigated RV function in patients who have pulmonary arterial hypertension with and without the BMPR2 mutation by combining in vivo measurements with molecular and histological analysis of human RV and left ventricular tissue.

Methods And Results: In total, 95 patients with idiopathic or familial pulmonary arterial hypertension were genetically screened for the presence of a BMPR2 mutation: 28 patients had a BMPR2 mutation, and 67 patients did not have a BMPR2 mutation. In vivo measurements were assessed using right heart catheterization and cardiac MRI. Despite a similar mean pulmonary artery pressure (noncarriers 54±15 versus mutation carriers 55±9 mm Hg) and pulmonary vascular resistance (755 [483-1043] versus 931 [624-1311] dynes·s(-1)·cm(-5)), mutation carriers presented with a more severely compromised RV function (RV ejection fraction: 37.6±12.8% versus 29.0±9%: P<0.05; cardiac index 2.7±0.9 versus 2.2±0.4 L·min(-1)·m(-2)). Differences continued to exist after treatment. To investigate the role of transforming growth factor β and bone morphogenetic protein receptor II signaling, human RV and left ventricular tissue were studied in controls (n=6), mutation carriers (n=5), and noncarriers (n=11). However, transforming growth factor β and bone morphogenetic protein receptor II signaling, and hypertrophy, apoptosis, fibrosis, capillary density, inflammation, and cardiac metabolism, as well, were similar between mutation carriers and noncarriers.

Conclusions: Despite a similar afterload, RV function is more severely affected in mutation carriers than in noncarriers. However, these differences cannot be explained by a differential transforming growth factor β, bone morphogenetic protein receptor II signaling, or cardiac adaptation.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.115.020696DOI Listing
May 2016

Are lung cysts in renal cell cancer (RCC) patients an indication for FLCN mutation analysis?

Fam Cancer 2016 Apr;15(2):297-300

Department of Urology, VU University Medical Center, Amsterdam, The Netherlands.

Renal cell cancer (RCC) represents 2-3% of all cancers and is the most lethal of the urologic malignancies, in a minority of cases caused by a genetic predisposition. Birt-Hogg-Dubé syndrome (BHD) is one of the hereditary renal cancer syndromes. As the histological subtype and clinical presentation in BHD are highly variable, this syndrome is easily missed. Lung cysts--mainly under the main carina--are reported to be present in over 90% of all BHD patients and might be an important clue in differentiating between sporadic RCC and BHD associated RCC. We conducted a retrospective study among patients diagnosed with sporadic RCC, wherein we retrospectively scored for the presence of lung cysts on thoracic CT. We performed FLCN mutation analysis in 8 RCC patients with at least one lung cysts under the carina. No mutations were identified. We compared the radiological findings in the FLCN negative patients to those in 4 known BHD patients and found multiple basal lung cysts were present significantly more frequent in FLCN mutation carriers and may be an indication for BHD syndrome in apparent sporadic RCC patients.
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http://dx.doi.org/10.1007/s10689-015-9853-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4803815PMC
April 2016

Impact of genotype on clinical course in arrhythmogenic right ventricular dysplasia/cardiomyopathy-associated mutation carriers.

Eur Heart J 2015 Apr 23;36(14):847-55. Epub 2015 Jan 23.

Department of Cardiology, University Medical Center Utrecht, Utrecht, The Netherlands Interuniversity Cardiology Institute of the Netherlands (ICIN), PO Box 19258, 3501 DG Utrecht, The Netherlands

Aims: We sought to determine the influence of genotype on clinical course and arrhythmic outcome among arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C)-associated mutation carriers.

Methods And Results: Pathogenic mutations in desmosomal and non-desmosomal genes were identified in 577 patients (241 families) from USA and Dutch ARVD/C cohorts. Patients with sudden cardiac death (SCD)/ventricular fibrillation (VF) at presentation (n = 36) were younger (median 23 vs. 36 years; P < 0.001) than those presenting with sustained monomorphic ventricular tachycardia (VT). Among 541 subjects presenting alive, over a mean follow-up of 6 ± 7 years, 12 (2%) patients died, 162 (30%) had sustained VT/VF, 78 (14%) manifested left ventricular dysfunction (EF < 55%), 28 (5%) experienced heart failure (HF), and 10 (2%) required cardiac transplantation. Patients (n = 22; 4%) with >1 mutation had significantly earlier occurrence of sustained VT/VF (mean age 28 ± 12 years), lower VT-/VF-free survival (P = 0.037), more frequent left ventricular dysfunction (29%), HF (19%) and cardiac transplantation (9%) when compared with those with only one mutation. Desmoplakin mutation carriers experienced more than four-fold occurrence of left ventricular dysfunction (40%) and HF (13%) than PKP2 carriers. Missense mutation carriers had similar death-/transplant-free survival and VT/VF penetrance (P = 0.137) when compared with those with truncating or splice site mutations. Men are more likely to be probands (P < 0.001), symptomatic (P < 0.001) and have earlier and more severe arrhythmic expression.

Conclusions: Presentation with SCD/VF occurs at a significantly younger age when compared with sustained monomorphic VT. The genotype of ARVD/C mutation carriers impacts clinical course and disease expression. Male sex negatively modifies phenotypic expression.
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http://dx.doi.org/10.1093/eurheartj/ehu509DOI Listing
April 2015

The pathogenesis of pneumothorax in Birt-Hogg-Dubé syndrome: a hypothesis.

Respirology 2014 Nov;19(8):1248-50

Department of Pulmonary Diseases, VU University Medical Center, Amsterdam, The Netherlands.

The development and natural course of lung cysts in patients with Birt-Hogg-Dubé syndrome (BHD) is still unclear, and the relationship between lung cysts and pneumothorax is not fully clarified. Based on the follow-up results of thoracic imaging in six patients with BHD, we hypothesize that decreased potential for stretching of the cysts' wall and extensive contact with the visceral pleura are probably responsible for rupture of the cyst wall resulting in increased risk for pneumothorax.
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http://dx.doi.org/10.1111/resp.12405DOI Listing
November 2014

Functional assessment of potential splice site variants in arrhythmogenic right ventricular dysplasia/cardiomyopathy.

Heart Rhythm 2014 Nov 31;11(11):2010-7. Epub 2014 Jul 31.

Department of Medical Genetics, University Medical Center Utrecht, Utrecht, The Netherlands. Electronic address:

Background: Interpretation of genetic screening results in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) often is difficult. Pathogenicity of variants with uncertain clinical significance may be predicted by software algorithms. However, functional assessment can unambiguously demonstrate the effect of such variants.

Objective: The purpose of this study was to perform functional analysis of potential splice site variants in ARVD/C patients.

Methods: Nine variants in desmosomal (PKP2, JUP, DSG2, DSC2) genes with potential RNA splicing effect were analyzed. The variants were found in patients who fulfilled 2010 ARVD/C Task Force Criteria (n = 7) or had suspected ARVD/C (n = 2). Total RNA was isolated from fresh blood samples and subjected to reverse transcriptase polymerase chain reaction.

Results: An effect on splicing was predicted by software algorithms for all variants. Of the 9 variants, 5 were intronic and 4 exonic. RNA analysis showed a functional effect on mRNA splicing by exon skipping, generation of new splice sites, or activation of cryptic sites in 6 variants. All 5 intronic variants tested severely impaired splicing. Only 1 of 4 exonic potential splice site variants was shown to have a deleterious effect on splicing. The remaining 3 exonic variants had no detectable effect on splicing, and heterozygous presence in mRNA confirmed biallelic expression.

Conclusion: Six variants of uncertain clinical significance in the PKP2, JUP, and DSG2 genes showed a deleterious effect on mRNA splicing, indicating these are ARVD/C-related pathogenic splice site mutations. These results highlight the importance of functional assessment of potential splice site variants to improve patient care and facilitate cascade screening.
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http://dx.doi.org/10.1016/j.hrthm.2014.07.041DOI Listing
November 2014

A de novo FLCN mutation in a patient with spontaneous pneumothorax and renal cancer; a clinical and molecular evaluation.

Fam Cancer 2013 Sep;12(3):373-9

Department of Clinical Genetics, VU University Medical Center, Amsterdam, The Netherlands,

Birt-Hogg-Dubé syndrome (BHD) is an autosomal dominant condition due to germline FLCN (folliculin) mutations, characterized by skin fibrofolliculomas, lung cysts, pneumothorax and renal cancer. We identified a de novo FLCN mutation, c.499C>T (p.Gln167X), in a patient who presented with spontaneous pneumothorax. Subsequently, typical skin features and asymptomatic renal cancer were diagnosed. Probably, de novo FLCN mutations are rare. However, they may be under-diagnosed if BHD is not considered in sporadic patients who present with one or more of the syndromic features. Genetic and immunohistochemical analysis of the renal tumour indicated features compatible with a tumour suppressor role of FLCN. The finding that mutant FLCN was expressed in the tumour might indicate residual functionality of mutant FLCN, a notion which will be explored in future studies.
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http://dx.doi.org/10.1007/s10689-012-9593-8DOI Listing
September 2013

Multiple myocardial crypts on modified long-axis view are a specific finding in pre-hypertrophic HCM mutation carriers.

Eur Heart J Cardiovasc Imaging 2012 Apr 24;13(4):292-7. Epub 2012 Jan 24.

Department of Cardiology, VU University Medical Center, De Boelelaan 1117, Amsterdam, The Netherlands.

Aims: Crypts can be found with cardiovascular magnetic resonance imaging (CMR) in hypertrophic cardiomyopathy (HCM) mutation carriers without hypertrophy (carriers) using a modified two-chamber view through the inferoseptum, but also in other patients and healthy individuals with standard long-axis views. Since it is currently unknown if carriers display a specific crypt morphology, we compared crypts in carriers with other cardiac pathologies (controls). Besides, we aimed to determine the optimal imaging plane for the detection of crypts by comparing modified two-chamber views with standard long-axis views. Finally, we evaluated the accuracy of crypts to identify carriers in HCM family screening.

Methods And Results: Standard CMR long-axis views with additional modified two-chamber views were prospectively performed in carriers (n= 43), consecutive CMR control patients (n= 252), and mutation-negative family members (n= 15). Crypts were found in 70% (30/43) of carriers and in 12% (31/252) of controls (P< 0.001). Crypts in carriers showed deeper penetrance into the myocardium compared with controls (74 ± 21% vs. 59 ± 22%, P< 0.01). Detection of two or more crypts had a sensitivity of 51% and specificity of 94% for carriership. Modified two-chamber views doubled the sensitivity to detect crypts compared with standard long-axis views. In family screening, ≥2 crypts had a 100% positive predictive value to identify carriers.

Conclusions: Multiple crypts in the absence of left ventricular hypertrophy are highly specific for HCM mutation carriership and warrant clinical follow-up. A modified two-chamber view has a superior sensitivity compared with standard long-axis views for crypt detection. CMR may be of additional value to identify carriers in family screening.
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http://dx.doi.org/10.1093/ehjci/jes005DOI Listing
April 2012

Familial multiple discoid fibromas: a look-alike of Birt-Hogg-Dubé syndrome not linked to the FLCN locus.

J Am Acad Dermatol 2012 Feb 26;66(2):259.e1-9. Epub 2011 Jul 26.

Birt-Hogg-Dubé Working Group, Department of Dermatology, VU University Medical Centre, Amsterdam, The Netherlands.

Background: Previously, we proposed that familial multiple trichodiscomas (OMIM 190340) is distinct from Birt-Hogg-Dubé syndrome (BHD) (OMIM #135150). BHD is characterized by multiple fibrofolliculomas/trichodiscomas, lung cysts, pneumothorax, and renal cell cancer. Germline FLCN mutations can be detected in most but not all BHD families.

Objective: We sought to evaluate familial multiple trichodiscomas at a clinical and genetic level. We now renamed this condition "familial multiple discoid fibromas" (FMDF) to emphasize the distinction from BHD.

Methods: In 8 additional families with an autosomal dominant pattern of multiple discoid fibromas we assessed the clinical findings and the histopathological features of skin lesions. FLCN germline mutation analysis was completed in 7 families. In two of these families segregation analysis was performed using polymorphic DNA markers in and around the FLCN locus.

Results: The clinical findings in FMDF are different from those in BHD with early onset of skin lesions, prominent involvement of the pinnae, and discoid fibromas without the follicular epithelial component characteristic of the fibrofolliculoma/trichodiscoma spectrum of BHD. In addition, there were no evident pulmonary or renal complications. In none of the families were pathogenic FLCN germline mutations identified. Using segregation analysis we could exclude involvement of the FLCN locus in the two kindreds tested.

Limitations: The prevalence of FMDF is presently unknown. The underlying gene defect has not yet been identified.

Conclusions: FMDF is clinically distinct from BHD and is not linked to the FLCN locus.
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http://dx.doi.org/10.1016/j.jaad.2010.11.039DOI Listing
February 2012

Arrhythmogenic right ventricular dysplasia/cardiomyopathy: pathogenic desmosome mutations in index-patients predict outcome of family screening: Dutch arrhythmogenic right ventricular dysplasia/cardiomyopathy genotype-phenotype follow-up study.

Circulation 2011 Jun 23;123(23):2690-700. Epub 2011 May 23.

Department of Cardiology, University Medical Center Utrecht, Utrecht, The Netherlands.

Background: Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is an autosomal dominant inherited disease with incomplete penetrance and variable expression. Causative mutations in genes encoding 5 desmosomal proteins are found in ≈50% of ARVD/C index patients. Previous genotype-phenotype relation studies involved mainly overt ARVD/C index patients, so follow-up data on relatives are scarce.

Methods And Results: One hundred forty-nine ARVD/C index patients (111 male patients; age, 49±13 years) according to 2010 Task Force criteria and 302 relatives from 93 families (282 asymptomatic; 135 male patients; age, 44±13 years) were clinically and genetically characterized. DNA analysis comprised sequencing of plakophilin-2 (PKP2), desmocollin-2, desmoglein-2, desmoplakin, and plakoglobin and multiplex ligation-dependent probe amplification to identify large deletions in PKP2. Pathogenic mutations were found in 87 index patients (58%), mainly truncating PKP2 mutations, including 3 cases with multiple mutations. Multiplex ligation-dependent probe amplification revealed 3 PKP2 exon deletions. ARVD/C was diagnosed in 31% of initially asymptomatic mutation-carrying relatives and 5% of initially asymptomatic relatives of index patients without mutation. Prolonged terminal activation duration was observed more than negative T waves in V(1) to V(3), especially in mutation-carrying relatives <20 years of age. In 45% of screened families, ≥1 affected relatives were identified (90% with mutations).

Conclusions: Pathogenic desmosomal gene mutations, mainly truncating PKP2 mutations, underlie ARVD/C in the majority (58%) of Dutch index patients and even 90% of familial cases. Additional multiplex ligation-dependent probe amplification analysis contributed to discovering pathogenic mutations underlying ARVD/C. Discovering pathogenic mutations in index patients enables those relatives who have a 6-fold increased risk of ARVD/C diagnosis to be identified. Prolonged terminal activation duration seems to be a first sign of ARVD/C in young asymptomatic relatives.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.110.988287DOI Listing
June 2011

Manifest disease, risk factors for sudden cardiac death, and cardiac events in a large nationwide cohort of predictively tested hypertrophic cardiomyopathy mutation carriers: determining the best cardiological screening strategy.

Eur Heart J 2011 May 1;32(9):1161-70. Epub 2011 Apr 1.

Department of Clinical Genetics, Academic Medical Centre, Amsterdam, the Netherlands.

Aims: We investigated the presence of a clinical diagnosis of hypertrophic cardiomyopathy (HCM), risk factors for sudden cardiac death (SCD), and cardiac events during follow-up in predictively tested-not known to have a clinical diagnosis of HCM before the DNA test-carriers of a sarcomeric gene mutation and associations with age and gender to determine the best cardiological screening strategy.

Methods And Results: One hundred and thirty-six (30%) of 446 mutation carriers were diagnosed with HCM at one or more cardiological evaluation(s). Male gender and higher age were associated with manifest disease. Incidence of newly diagnosed manifest HCM was <10% per person-year under the age of 40 years and >10% in older carriers, although numbers were small in carriers <15 years. Twenty-three percent of carriers, with and without manifest disease, had established risk factor(s) for SCD (no significant difference). During an average follow-up of 3.5 ± 1.7 years two carriers, both with manifest disease, died suddenly (0.13% per person-year). A high-risk status for SCD (≥2 risk factors and manifest HCM) was present in 17 carriers during follow-up (2.4% per person-year). Age but not gender was associated with a high-risk status for SCD.

Conclusion: Thirty percent of carriers had or developed manifest HCM after predictive DNA testing and risk factors for SCD were frequently present. Our data suggest that the SCD risk is low and risk stratification for SCD can be omitted in carriers without manifest disease and that frequency of cardiological evaluations can possibly be decreased in carriers between 15 and 40 years as long as hypertrophy is absent.
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http://dx.doi.org/10.1093/eurheartj/ehr092DOI Listing
May 2011

Arrhythmogenic right ventricular dysplasia/cardiomyopathy diagnostic task force criteria: impact of new task force criteria.

Circ Arrhythm Electrophysiol 2010 Apr 9;3(2):126-33. Epub 2010 Mar 9.

Department of Cardiology, University Medical Center Utrecht, 3584 CX Utrecht, The Netherlands.

Background: Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C) Diagnostic Task Force Criteria (TFC) proposed in 1994 are highly specific but lack sensitivity. A new international task force modified criteria to improve diagnostic yield. A comparison of diagnosis by 1994 TFC versus newly proposed criteria in 3 patient groups was conducted.

Methods And Results: In new TFC, scoring by major and minor criteria is maintained. Structural abnormalities are quantified and TFC highly specific for ARVD/C upgraded to major. Furthermore, new criteria are added: terminal activation duration of QRS > or = 55 ms, ventricular tachycardia with left bundle-branch block morphology and superior axis, and genetic criteria. Three groups were studied: (1) 105 patients with proven ARVD/C according to 1994 TFC, (2) 89 of their family members, and (3) 39 patients with probable ARVD/C (ie, 3 points by 1994 TFC). All were screened for pathogenic mutations in desmosomal genes. Three ARVD/C patients did not meet the new sharpened criteria on structural abnormalities and thereby did not fulfill new TFC. In 62 of 105 patients with proven ARVD/C, mutations were found: 58 in the gene encoding Plakophilin2 (PKP2), 3 in Desmoglein2, 3 in Desmocollin2, and 1 in Desmoplakin. Three patients had bigenic involvement. Ten additional relatives (11%) fulfilled new TFC: 9 (90%) were female, and all carried PKP2 mutations. No relatives lost diagnosis by application of new TFC. Of patients with probable ARVD/C, 25 (64%) fulfilled new TFC: 8 (40%) women and 14 (56%) carrying pathogenic mutations.

Conclusions: In this first study applying new TFC to patients suspected of ARVD/C, 64% of probable ARVD/C patients and 11% of family members were additionally diagnosed. ECG criteria and pathogenic mutations especially contributed to new diagnosis. Newly proposed TFC have a major impact in increasing diagnostic yield of ARVD/C.
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http://dx.doi.org/10.1161/CIRCEP.109.927202DOI Listing
April 2010

Variable phenotypic manifestation of IRF6 mutations in the Van der Woude syndrome and popliteal pterygium syndrome: implications for genetic counseling.

Clin Dysmorphol 2009 Oct;18(4):225-7

Department of Clinical Genetics and Human Genetics, VU University Medical Center, ACTA, Amsterdam, The Netherlands.

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http://dx.doi.org/10.1097/MCD.0b013e32832d4a87DOI Listing
October 2009

Distinct regulation of developmental and heart disease-induced atrial natriuretic factor expression by two separate distal sequences.

Circ Res 2008 Apr 14;102(7):849-59. Epub 2008 Feb 14.

Heart Failure Research Center, AMC, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.

Nppa, encoding atrial natriuretic factor, is expressed in fetal atrial and ventricular myocardium and is downregulated in the ventricles after birth. During hypertrophy and heart failure, Nppa expression is reactivated in the ventricles and serves as a highly conserved marker of heart disease. The Nppa promoter has become a frequently used model to study mechanisms of cardiac gene regulation. Nevertheless, the regulatory sequences that provide the correct developmental pattern and ventricular reactivation during cardiac disease remain to be defined. We found that proximal Nppa fragments ranging from 250 bp to 16 kbp provide robust reporter gene activity in the atria and correct repression in the atrioventricular canal and the nodes of the conduction system in vivo. However, depending on fragment size and site of integration into the genome of mice, the fetal ventricular activity was either absent or present in an incorrect pattern. Furthermore, these fragments did not provide ventricular reactivation in heart disease models. These results indicate that the proximal promoter does not provide a physiologically relevant model for ventricular gene activity. In contrast, 2 modified bacterial artificial chromosome clones with partially overlapping genomic Nppa sequences provided appropriate reactivation of the green fluorescent protein reporter during pressure overload-induced hypertrophy and heart failure in vivo. However, only 1 of these bacterial artificial chromosomes provided correct fetal ventricular green fluorescent protein activity. These results show that distinct distal regulatory sequences and divergent regulatory pathways control fetal ventricular activity and reactivation of Nppa during cardiac disease, respectively.
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http://dx.doi.org/10.1161/CIRCRESAHA.107.170571DOI Listing
April 2008