Marieke J.H. Baars

Deficiency of knowledge of genetics and genetic tests among general practitioners, gynecologists, and pediatricians: A global problem

Purpose: The objective of this study was to assess knowledge of genetics and awareness of genetic tests among Dutch general practitioners (GPs), gynecologists (GYNs), and pediatricians (PEDs), as well as factors influencing their knowledge and awareness.Methods: An anonymous questionnaire inquiry was used, validated with a sample of 52 clinical geneticists (CGs). The study was carried out in primary care (general practice) and secondary care (general and university hospitals) in The Netherlands. A random sample of 200 GPs, 300 GYNs, and 265 PEDs received a questionnaire. In addition, all registered CGs (58) received a questionnaire for validation. In total, 122 GPs, 187 GYNs, 164 PEDs, and 52 CGs returned a completed questionnaire. The main outcome measures were differences in knowledge scores between physicians working in different disciplines and factors influencing these scores.Results: Knowledge scores of GPs (mean 64% correct answers, 61%–66% [95% confidence interval]), GYNs (mean 75% correct answers, 73%–76% [95% confidence interval]), and PEDs (mean 81% correct answers, 79%–82% [95% confidence interval]) were lower than those in the CG validation group (mean 95% correct answers, 94%–96% [95% confidence interval]). The 5th percentile of GPs, GYNs, and PEDs was at approximately 40%, 52% and 62% correct answers, respectively. There was a specific lack of knowledge about DNA testing. In addition to specialty, important factors positively associated with the knowledge scores of nongeneticists are more recent graduation, having taken an elective course in genetics, and providing genetic counseling in their own practice.Conclusion: The overall knowledge levels of genetics in many nongeneticist health care providers show clear deficiencies. This is in line with reports from other countries, showing that these deficiencies are a global problem.

Two cases of severe neonatal hypertrophic cardiomyopathy caused by compound heterozygous mutations in the MYBPC3 gene

Background: Idiopathic (primary) hypertrophic cardiomyopathy (HCM) is mainly caused by mutations in genes encoding sarcomeric proteins. One of the most commonly mutated HCM genes is the myosin binding protein C (MYBPC3) gene. Mutations in this gene lead mainly to truncation of the protein which gives rise to a relatively mild phenotype. Pure HCM in neonates is rare and most of the time childhood HCM occurs in association with another underlying condition. Objective: To study the presence of mutations in the MYBPC3 gene in idiopathic childhood HCM. Methods:MYBPC3 coding region and splice junction variation were analysed by denaturing high performance liquid chromatography (DHPLC) and sequencing in DNA isolated from two neonates with severe unexplained HCM, who died within the first weeks of life. Results: Truncating mutations were found in both alleles of the MYBPC3 gene in both patients, suggesting there was no functional copy of the MYBPC3 protein. Patient 1 carried the maternally inherited c.2373_2374insG mutation and the paternally inherited splice-donor site mutation c.1624+1G→A. Patient 2 carried the maternally inherited frameshift mutation c.3288delA (p.Glu1096fsX92) and the paternally inherited non-sense mutation c.2827C→T (p.Arg943X). Conclusions: The findings indicate the need for mutation analysis of genes encoding sarcomeric proteins in childhood HCM and the possibility of compound heterozygosity.

Losartan therapy in adults with Marfan syndrome: study protocol of the multi-center randomized controlled COMPARE trial

BackgroundMarfan syndrome (MFS) is one of the most common systemic disorders of connective tissue with the incidence of approximately 2-3 per 10 000 individuals. Aortic disease, leading to progressive aneurysmal dilatation and dissection is the main cause of morbidity and mortality of Marfan patients. Current treatment (e.g. beta blockers and elective surgery) does postpone but cannot prevent aortic complications in these patients. Recent studies have found Transforming Growth Factor β (TGF β) to be involved in the aortic aneurysm formation. Losartan, an Angiotensin II type 1 receptor blocker inhibits TGFβ in a mouse model of Marfan syndrome leading to inhibition of aortic growth. The main objective of this trial is to assess whether losartan treatment leads to a clinically relevant decrease of aortic dilatation in adult patients with Marfan syndrome.Methods/DesignCOMPARE study (COzaar in Marfan Patients Reduces aortic Enlargement) is an open-label, randomized, controlled trial with blinded end-points. Treatment with losartan will be compared with no additional treatment after 3 years of follow-up. We will enroll 330 patients with MFS who will be randomly assigned to receive losartan or not. Patients taking beta-blockers will continue taking their standard treatment. The primary end-point is the largest change in aortic diameter at any aortic level measured by means of MRI. Secondary end-points are change in mortality, incidence of dissection, elective aortic surgery, aortic volume, aortic stiffness and ventricular function. We will also investigate gene and protein expression change in the skin under losartan therapy and create prediction models for losartan-treatment response and aortic dilatation.DiscussionThe COMPARE study will provide important evidence of effects of losartan treatment in adult Marfan patient population. We expect losartan to significantly reduce the occurrence and progression of aortic dilatation. This trial investigates a wide spectrum of clinical, genetic and biochemical effects of losartan aiming to provide further insight in the pathogenesis and treatment of Marfan syndrome.Trial registrationNetherlands Trial Register NTR1423.

HCN4 Mutations in Multiple Families With Bradycardia and Left Ventricular Noncompaction Cardiomyopathy

BACKGROUND Familial forms of primary sinus bradycardia have sometimes been attributed to mutations in HCN4, SCN5A, and ANK2. In these studies, no structural cardiac alterations were reported in mutation carriers. However, a cluster of reports in the literature describe patients presenting with sinus bradycardia in association with left ventricular noncompaction cardiomyopathy (LVNC), pointing to a shared genetic cause. OBJECTIVES This study sought to identify the genetic defect underlying the combined clinical presentation of bradycardia and LVNC, hypothesizing that these 2 clinical abnormalities have a common genetic cause. METHODS Exome sequencing was carried out in 2 cousins from the index family that were affected by the combined bradycardia-LVNC phenotype; shared variants thus identified were subsequently overlaid with the chromosomal regions shared among 5 affected family members that were identified using single nucleotide polymorphism array analysis. RESULTS The combined linkage analysis and exome sequencing in the index family identified 11 novel variants shared among the 2 affected cousins. One of these, p.Gly482Arg in HCN4, segregated with the combined bradycardia and LVNC phenotype in the entire family. Subsequent screening of HCN4 in 3 additional families with the same clinical combination of bradycardia and LVNC identified HCN4 mutations in each. In electrophysiological studies, all found HCN4 mutations showed a more negative voltage dependence of activation, consistent with the observed bradycardia. CONCLUSIONS Although mutations in HCN4 have been previously linked to bradycardia, our study provides the first evidence to our knowledge that mutations in this ion channel gene also may be associated with structural abnormalities of the myocardium.

Mutations in the sarcomere gene MYH7 in Ebstein anomaly

Background—Ebstein anomaly is a rare congenital heart malformation characterized by adherence of the septal and posterior leaflets of the tricuspid valve to the underlying myocardium. An association between Ebstein anomaly with left ventricular noncompaction (LVNC) and mutations in MYH7 encoding &bgr;-myosin heavy chain has been shown; in this report, we have screened for MYH7 mutations in a cohort of probands with Ebstein anomaly in a large population-based study. Methods and Results—Mutational analysis in a cohort of 141 unrelated probands with Ebstein anomaly was performed by next-generation sequencing and direct DNA sequencing of MYH7. Heterozygous mutations were identified in 8 of 141 samples (6%). Seven distinct mutations were found; 5 were novel and 2 were known to cause hypertrophic cardiomyopathy. All mutations except for 1 3-bp deletion were missense mutations; 1 was a de novo change. Mutation-positive probands and family members showed various congenital heart malformations as well as LVNC. Among 8 mutation-positive probands, 6 had LVNC, whereas among 133 mutation-negative probands, none had LVNC. The frequency of MYH7 mutations was significantly different between probands with and without LVNC accompanying Ebstein anomaly (P<0.0001). LVNC segregated with the MYH7 mutation in the pedigrees of 3 of the probands, 1 of which also included another individual with Ebstein anomaly. Conclusions—Ebstein anomaly is a congenital heart malformation that is associated with mutations in MYH7. MYH7 mutations are predominantly found in Ebstein anomaly associated with LVNC and may warrant genetic testing and family evaluation in this subset of patients.

Deficient knowledge of genetics relevant for daily practice among medical students nearing graduation.

Purpose: The objective of this study was to investigate whether the knowledge of genetics relevant for daily practice among medical students nearing graduation in the Netherlands was sufficient to react appropriately to the change of relevance of genetics in medicine.Methods: A computer examination validated in a group of clinical geneticists, medical students nearing graduation, and nonmedical students. The examination consisted of 215 genetic questions classified by the designers into three categories of relevance: “essential” knowledge (requirement: > 95% correct answers), “desirable” knowledge (requirement: > 60% correct answers), and “too specialized” knowledge (no requirement). To set an independent standard, the questions were also judged by clinical geneticists and nongenetic health care providers in an Angoff procedure. In total, 291 medical students nearing graduation from seven out of the eight medical schools in the Netherlands participated.Results: As expected, the mean score for “essential” knowledge (71.63%, 95% CI 70.74–72.52) was higher than for “desirable” knowledge (55.99%, 95% CI 55.08–56.90); the mean score for “too specialized” knowledge (44.40%, 95% CI 43.19–45.62) was the lowest. According to passing scores set for “essential” knowledge as defined by the designers, the clinical geneticists, and the nongenetic health care providers, only 0%, 26%, and 3%, respectively, of the participants would have passed.Conclusions: Medical students nearing graduation lack genetic knowledge that is essential for daily practice. Therefore, changes should be made in the medical curricula.

Mild phenotypes in a series of patients with Opitz GBBB syndrome with MID1 mutations

Opitz syndrome (OS; MIM 145410 and MIM 300000) is a congenital midline malformation syndrome characterized by hypertelorism, hypospadias, cleft lip/palate, laryngotracheoesophageal (LTE) abnormalities, imperforate anus, developmental delay, and cardiac defects. The X‐linked form (XLOS) is caused by mutations in the MID1 gene, which encodes a microtubule‐associated RBCC protein. In this study, phenotypic manifestations of patients with and without MID1 mutations were compared to determine genotype‐phenotype correlations. We detected 10 novel mutations, 5 in familial cases, 2 in sporadic cases, and 3 in families for whom it was not clear if they were familial or sporadic. The genotype and phenotype was compared for these 10 families, clinically diagnosed OS patients found not to have MID1 mutations, and 4 families in whom we have previously reported MID1 mutations. This combined data set includes clinical and mutation data on 70 patients. The XLOS patients with MID1 mutations were less severely affected than patients with MID1 mutations reported in previous studies, particularly in functionally significant neurologic, LTE, anal, and cardiac abnormalities. Minor anomalies were more prevalent in patients with MID1 mutations compared to those without mutations in this study. Female MID1 mutation carriers had milder phenotypes compared to male MID1 mutation carriers, with the most common manifestation being hypertelorism in both sexes. Most of the anomalies found in the patients of the present study do not correlate with the MID1 mutation type, with the possible exception of LTE malformations. This study demonstrates the wide spectrum of severity and manifestations of OS. It also shows that XLOS patients with MID1 mutations may be less severely affected than indicated in prior reports.

22q11.2 Deletion Syndrome is under-recognised in adult patients with tetralogy of Fallot and pulmonary atresia

Background Three quarters of patients with 22q11.2 Deletion Syndrome (22q11.2DS) have congenital heart disease (CHD), typically conotruncal heart defects. Although it is currently common practice to test all children with typical CHD for 22q11.2DS, many adult patients have not been tested in the past and therefore 22q11.2DS might be under-recognised in adults. Objectives To determine the prevalence of 22q11.2DS in adults with tetralogy of Fallot (TOF) and pulmonary atresia (PA)/ventricular septal defect (VSD) and to assess the level of recognition of the syndrome in adult patients. Methods Patients were identified from CONCOR, a nationwide registry for adult patients with CHD. Inclusion criteria were diagnosis of TOF or PA/VSD and the availability of DNA. Patients with syndromes other than 22q11.2DS were excluded. Multiplex ligation-dependent probe amplification was used to detect 22q11.2 microdeletions. Results 479 patients with TOF and 79 patients with PA/VSD (56% male, median age 34.7 years) were included and analysed. Twenty patients were already known to have 22q11.2DS. A 22q11.2 microdeletion was detected in a further 24 patients. Thirty-one patients with TOF (6.5%) had 22q11.2DS, whereas 13 patients with PA/VSD had 22q11.2DS (16.5%). Of all 22q11.2 microdeletions, 54% (24/44) were unknown before this study. Conclusion This study shows that although the prevalence of 22q11.2DS in adults with TOF and PA/VSD is substantial, it is unrecognised in more than half of patients. As the syndrome has important clinical and reproductive implications, a diagnostic test should be considered in all adult patients with TOF and PA/VSD.

Inflammation aggravates disease severity in Marfan syndrome patients.

Background Marfan syndrome (MFS) is a pleiotropic genetic disorder with major features in cardiovascular, ocular and skeletal systems, associated with large clinical variability. Numerous studies reveal an involvement of TGF-β signaling. However, the contribution of tissue inflammation is not addressed so far. Methodology/Principal Findings Here we showed that both TGF-β and inflammation are up-regulated in patients with MFS. We analyzed transcriptome-wide gene expression in 55 MFS patients using Affymetrix Human Exon 1.0 ST Array and levels of TGF-β and various cytokines in their plasma. Within our MFS population, increased plasma levels of TGF-β were found especially in MFS patients with aortic root dilatation (124 pg/ml), when compared to MFS patients with normal aorta (10 pg/ml; p = 8×10−6, 95% CI: 70–159 pg/ml). Interestingly, our microarray data show that increased expression of inflammatory genes was associated with major clinical features within the MFS patients group; namely severity of the aortic root dilatation (HLA-DRB1 and HLA-DRB5 genes; r = 0.56 for both; False Discovery Rate(FDR) = 0%), ocular lens dislocation (RAET1L, CCL19 and HLA-DQB2; Fold Change (FC) = 1.8; 1.4; 1.5, FDR = 0%) and specific skeletal features (HLA-DRB1, HLA-DRB5, GZMK; FC = 8.8, 7.1, 1.3; FDR = 0%). Patients with progressive aortic disease had higher levels of Macrophage Colony Stimulating Factor (M-CSF) in blood. When comparing MFS aortic root vessel wall with non-MFS aortic root, increased numbers of CD4+ T-cells were found in the media (p = 0.02) and increased number of CD8+ T-cells (p = 0.003) in the adventitia of the MFS patients. Conclusion/Significance In conclusion, our results imply a modifying role of inflammation in MFS. Inflammation might be a novel therapeutic target in these patients.

Ebstein anomaly associated with left ventricular noncompaction: An autosomal dominant condition that can be caused by mutations in MYH7

Left ventricular noncompaction (LVNC) is a relatively common genetic cardiomyopathy, characterized by prominent trabeculations with deep intertrabecular recesses in mainly the left ventricle. Although LVNC often occurs in an isolated entity, it may also be present in various types of congenital heart disease (CHD). The most prevalent CHD in LVNC is Ebstein anomaly, which is a rare form of CHD characterized by apical displacement and partial fusion of the septal and posterior leaflet of the tricuspid valve with the ventricular septum. Several reports of sporadic as well as familial cases of Ebstein anomaly associated with LVNC have been reported. Recent studies identified mutations in the MYH7 gene, encoding the sarcomeric β‐myosin heavy chain protein, in patients harboring this specific phenotype. Here, we will review the association between Ebstein anomaly, LVNC and mutations in MYH7, which seems to represent a subtype of Ebstein anomaly with autosomal dominant inheritance and variable penetrance.