Mitochondrial MICOS complex genes, implicated in hypoplastic left heart syndrome, maintain cardiac contractility and actomyosin integrity

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart disease (CHD) with a likely oligogenic etiology, but our understanding of the genetic complexities and pathogenic mechanisms leading to HLHS is limited. We therefore performed whole genome sequencing (WGS) on a large cohort of HLHS patients and their families to identify candidate genes that were then tested in Drosophila heart model for functional and structural requirements. Bioinformatic analysis of WGS data from an index family comprised of a HLHS proband born to consanguineous parents and postulated to have a homozygous recessive disease etiology, prioritized 9 candidate genes with rare, predicted damaging homozygous variants. Of the candidate HLHS gene homologs tested, cardiac-specific knockdown (KD) of mitochondrial MICOS complex subunit Chchd3/6 resulted in drastically compromised heart contractility, diminished levels of sarcomeric actin and myosin, reduced cardiac ATP levels, and mitochondrial fission-fusion defects. Interestingly, these heart defects were similar to those inflicted by cardiac KD of ATP synthase subunits of the electron transport chain (ETC), consistent with the MICOS complex's role in maintaining cristae morphology and ETC complex assembly. Analysis of 183 genomes of HLHS patient-parent trios revealed five additional HLHS probands with rare, predicted damaging variants in CHCHD3 or CHCHD6. Hypothesizing an oligogenic basis for HLHS, we tested 60 additional prioritized candidate genes in these cases for genetic interactions with Chchd3/6 in sensitized fly hearts. Moderate KD of Chchd3/6 in combination with Cdk12 (activator of RNA polymerase II), RNF149 (goliath, gol, E3 ubiquitin ligase), or SPTBN1 (β Spectrin, β-Spec, scaffolding protein) caused synergistic heart defects, suggesting the potential involvement of a diverse set of pathways in HLHS. Further elucidation of novel candidate genes and genetic interactions of potentially disease-contributing pathways is expected to lead to a better understanding of HLHS and other CHDs.

Isolated Absent Aortic Valve: A Unique Fetal Case With Echocardiographic, Pathologic, and Genetic Correlation

We present a 22-week fetus with isolated absent aortic valve and inverse circular shunt. The pregnancy was interrupted. Here, echocardiography and pathology images demonstrate this rare entity. Whole genome sequencing revealed a potentially disease-causing variant in the APC gene. Whole genome sequencing should be considered in severe and rare fetal diseases. (Level of Difficulty: Advanced.).

Endothelial Loss of ETS1 Impairs Coronary Vascular Development and Leads to Ventricular Non-Compaction

RATIONALE

Jacobsen syndrome is a rare chromosomal disorder caused by deletions in the long arm of human chromosome 11, resulting in multiple developmental defects including congenital heart defects. Combined studies in humans and genetically engineered mice implicate that loss of ETS1 (E26 transformation specific 1) is the cause of congenital heart defects in Jacobsen syndrome, but the underlying molecular and cellular mechanisms are unknown.

OBJECTIVE

To determine the role of ETS1 in heart development, specifically its roles in coronary endothelium and endocardium and the mechanisms by which loss of ETS1 causes coronary vascular defects and ventricular noncompaction.

METHODS AND RESULTS

ETS1 global and endothelial-specific knockout mice were used. Phenotypic assessments, RNA sequencing, and chromatin immunoprecipitation analysis were performed together with expression analysis, immunofluorescence and RNAscope in situ hybridization to uncover phenotypic and transcriptomic changes in response to loss of ETS1. Loss of ETS1 in endothelial cells causes ventricular noncompaction, reproducing the phenotype arising from global deletion of ETS1. Endothelial-specific deletion of ETS1 decreased the levels of Alk1 (activin receptor-like kinase 1), Cldn5 (claudin 5), Sox18 (SRY-box transcription factor 18), Robo4 (roundabout guidance receptor 4), Esm1 (endothelial cell specific molecule 1) and Kdr (kinase insert domain receptor), 6 important angiogenesis-relevant genes in endothelial cells, causing a coronary vasculature developmental defect in association with decreased compact zone cardiomyocyte proliferation. Downregulation of ALK1 expression in endocardium due to the loss of ETS1, along with the upregulation of TGF (transforming growth factor)-β1 and TGF-β3, occurred with increased TGFBR2/TGFBR1/SMAD2 signaling and increased extracellular matrix expression in the trabecular layer, in association with increased trabecular cardiomyocyte proliferation.

CONCLUSIONS

These results demonstrate the importance of endothelial and endocardial ETS1 in cardiac development. Delineation of the gene regulatory network involving ETS1 in heart development will enhance our understanding of the molecular mechanisms underlying ventricular and coronary vascular developmental defects and will lead to improved approaches for the treatment of patients with congenital heart disease.

ETS1 and HLHS: Implications for the Role of the Endocardium

We have identified the ETS1 gene as the cause of congenital heart defects, including an unprecedented high frequency of HLHS, in the chromosomal disorder Jacobsen syndrome. Studies in Ciona intestinalis demonstrated a critical role for ETS1 in heart cell fate determination and cell migration, suggesting that the impairment of one or both processes can underlie the pathogenesis of HLHS. Our studies determined that ETS1 is expressed in the cardiac neural crest and endocardium in the developing murine heart, implicating one or both lineages in the development of HLHS. Studies in Drosophila and Xenopus demonstrated a critical role for ETS1 in regulating cardiac cell fate determination, and results in Xenopus provided further evidence for the role of the endocardium in the evolution of the “hypoplastic” HLHS LV. Paradoxically, these studies suggest that the loss of ETS1 may cause a cell fate switch resulting in the loss of endocardial cells and a relative abundance of cardiac myocytes. These studies implicate an “HLHS transcriptional network” of genes conserved across species that are essential for early heart development. Finally, the evidence suggests that in a subset of HLHS patients, the HLHS LV cardiac myocytes are, intrinsically, developmentally and functionally normal, which has important implications for potential future therapies.

High Level of Serum Uric Acid induced Monocyte Inflammation is Related to Coronary Calcium Deposition in the Middle-Aged and Elder Population of China: A five-year Prospective Cohort Study

Background

Serum uric acid (SUA) is suspected to be associated with atherosclerosis and calcium deposition in atherosclerosis is known to related poor prognosis, yet there is no cohort study on the aged in China. We aimed to investigate the relationships between SUA levels and coronary calcium deposition in the middle-aged and elderly populations in China.

Methods

A total of 326 participants between the ages of 50 and 85 who had undergone a coronary CT scan in 2015 at the Huadong Hospital Affiliated to Fudan University (Shanghai, China) were included in this study. Univariate and multivariate binary logistic regression was performed to analyze the correlation between SUA levels and coronary artery calcium score (CACS). The changes in CACS during a five-year follow-up were analyzed through Kaplan–Meier survival and binary cox regression analysis. An observational study was done on another 104 asymptomatic middle-aged and elderly patients to compare relative mRNA expressions of proinflammatory factors in peripheral blood mononuclear cells (PBMCs) from 104 subjects.

Results

Based on the first year of follow-up data analysis, the elevation of SUA levels (P<0.001) is an independent risk factor for the increase of CACS after coordinating the confounding factors. According to five-year follow-up data, cox regression analysis proved that SUA was a risk factor for CACS (HR =5.86, P<0.001). The mRNA expression of IL-6 and CXCL8 in the HUA and HUA patients with CAC (HUA-CAC) groups was significantly higher than that in the normal control (NC) and coronary calcium deposition (CAC) groups.

Conclusion

Taken together, the findings in this study indicate that high SUA levels (P<0.001) are an independent risk factor for CACS and elevated SUA levels increase the risk of developing coronary calcium deposition among middle-aged and old people in the Chinese population, which may be related to an increase of pro-inflammatory cytokines in the PBMCs.

Combined Non-Invasive Cardiac Imaging and Genetic Testing of Elite Volleyball Players: A Ten-Year Experience

Sudden cardiac death in athletes is a devastating event. Although significant progress has been made in identifying the underlying pathophysiology and genetic basis for sudden cardiac death in young athletes, controversy exists regarding cost-effective screening measures to identify at-risk individuals. In this report we describe our ten-year experience performing cardiovascular assessments on 150 members of the United States Men’s and Women’s National Volleyball teams. Through a combination of history, physical, echocardiography and genetic testing, we have identified one previously undiagnosed athlete with Marfan syndrome, along with four others with a possible aortopathy. Taken together, this approach is a cost-effective strategy for the identification of at-risk tall athletes leading to potentially lifesaving interventions, and raises the issue of the feasibility of screening for all tall individuals.

The Needle in the Haystack-Searching for Genetic and Epigenetic Differences in Monozygotic Twins Discordant for Tetralogy of Fallot

Congenital heart defects (CHDs) are the most common birth defect in human with an incidence of almost 1% of all live births. Most cases have a multifactorial origin with both genetics and the environment playing a role in its development and progression. Adding an epigenetic component to this aspect is exemplified by monozygotic twins which share the same genetic background but have a different disease status. As a result, the interplay between the genetic, epigenetic and the environmental conditions might contribute to the etiology and phenotype. To date, the underlying causes of the majority of CHDs remain poorly understood. In this study, we performed genome-wide high-throughput sequencing to examine the genetic, structural genomic and epigenetic differences of two identical twin pairs discordant for Tetralogy of Fallot (TOF), representing the most common cyanotic form of CHDs. Our results show the almost identical genetic and structural genomic identity of the twins. In contrast, several epigenetic alterations could be observed given by DNA methylation changes in regulatory regions of known cardiac-relevant genes. Overall, this study provides first insights into the impact of genetic and especially epigenetic factors underlying monozygotic twins discordant for CHD like TOF.

Patient-specific genomics and cross-species functional analysis implicate LRP2 in hypoplastic left heart syndrome

Congenital heart diseases (CHDs), including hypoplastic left heart syndrome (HLHS), are genetically complex and poorly understood. Here, a multidisciplinary platform was established to functionally evaluate novel CHD gene candidates, based on whole-genome and iPSC RNA sequencing of a HLHS family-trio. Filtering for rare variants and altered expression in proband iPSCs prioritized 10 candidates. siRNA/RNAi-mediated knockdown in healthy human iPSC-derived cardiomyocytes (hiPSC-CM) and in developing Drosophila and zebrafish hearts revealed that LDL receptor-related protein LRP2 is required for cardiomyocyte proliferation and differentiation. Consistent with hypoplastic heart defects, compared to patents the proband's iPSC-CMs exhibited reduced proliferation. Interestingly, rare, predicted-damaging LRP2 variants were enriched in a HLHS cohort; however, understanding their contribution to HLHS requires further investigation. Collectively, we have established a multi-species high-throughput platform to rapidly evaluate candidate genes and their interactions during heart development, which are crucial first steps toward deciphering oligogenic underpinnings of CHDs, including hypoplastic left hearts.

Intrinsic Endocardial Defects Contribute to Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS) is a complex congenital heart disease characterized by abnormalities in the left ventricle, associated valves, and ascending aorta. Studies have shown intrinsic myocardial defects but do not sufficiently explain developmental defects in the endocardial-derived cardiac valve, septum, and vasculature. Here, we identify a developmentally impaired endocardial population in HLHS through single-cell RNA profiling of hiPSC-derived endocardium and human fetal heart tissue with an underdeveloped left ventricle. Intrinsic endocardial defects contribute to abnormal endothelial-to-mesenchymal transition, NOTCH signaling, and extracellular matrix organization, key factors in valve formation. Endocardial abnormalities cause reduced cardiomyocyte proliferation and maturation by disrupting fibronectin-integrin signaling, consistent with recently described de novo HLHS mutations associated with abnormal endocardial gene and fibronectin regulation. Together, these results reveal a critical role for endocardium in HLHS etiology and provide a rationale for considering endocardial function in regenerative strategies.

Model system identification of novel congenital heart disease gene candidates: focus on RPL13

Genetics is a significant factor contributing to congenital heart disease (CHD), but our understanding of the genetic players and networks involved in CHD pathogenesis is limited. Here, we searched for de novo copy number variations (CNVs) in a cohort of 167 CHD patients to identify DNA segments containing potential pathogenic genes. Our search focused on new candidate disease genes within 19 deleted de novo CNVs, which did not cover known CHD genes. For this study, we developed an integrated high-throughput phenotypical platform to probe for defects in cardiogenesis and cardiac output in human induced pluripotent stem cell (iPSC)-derived multipotent cardiac progenitor (MCPs) cells and, in parallel, in the Drosophila in vivo heart model. Notably, knockdown (KD) in MCPs of RPL13, a ribosomal gene and SON, an RNA splicing cofactor, reduced proliferation and differentiation of cardiomyocytes, while increasing fibroblasts. In the fly, heart-specific RpL13 KD, predominantly at embryonic stages, resulted in a striking 'no heart' phenotype. KD of Son and Pdss2, among others, caused structural and functional defects, including reduced or abolished contractility, respectively. In summary, using a combination of human genetics and cardiac model systems, we identified new genes as candidates for causing human CHD, with particular emphasis on ribosomal genes, such as RPL13. This powerful, novel approach of combining cardiac phenotyping in human MCPs and in the in vivo Drosophila heart at high throughput will allow for testing large numbers of CHD candidates, based on patient genomic data, and for building upon existing genetic networks involved in heart development and disease.

Partial Jacobsen syndrome phenotype in a patient with a de novo frameshift mutation in the ETS1 transcription factor

Jacobsen syndrome (OMIM #147791) is a rare contiguous gene disorder caused by deletions in distal 11q. The clinical phenotype is variable and can include dysmorphic features, varying degrees of intellectual disability, behavioral problems including autism and attention deficit hyperactivity disorder, congenital heart defects, structural kidney defects, genitourinary problems, immunodeficiency, and a bleeding disorder due to impaired platelet production and function. Previous studies combining both human and animal systems have implicated several disease-causing genes in distal 11q that contribute to the Jacobsen syndrome phenotype. One gene, ETS1, has been implicated in causing congenital heart defects, structural kidney defects, and immunodeficiency. We performed a comprehensive phenotypic analysis on a patient with congenital heart disease previously found to have a de novo frameshift mutation in ETS1, resulting in the loss of the DNA-binding domain of the protein. Our results suggest that loss of Ets1 causes a “partial Jacobsen syndrome phenotype” including congenital heart disease, facial dysmorphism, intellectual disability, and attention deficit hyperactivity disorder.

Successful Management of a Patient With Jacobsen Syndrome and Hypoplastic Left Heart Syndrome

Jacobsen syndrome (JS) is a rare genetic condition characterized by intellectual disability, hematologic abnormalities, and congenital heart defects. A male infant presented at birth with phenotypic findings of JS and echocardiographic findings of hypoplastic left heart syndrome (HLHS). Array comparative genomic hybridization was performed at age three days and revealed an 8.1 Mb terminal deletion on the long arm of chromosome 11, consistent with JS. At five days of age, a hybrid stage 1 procedure was performed. At age 46 days, he underwent a Norwood operation followed by bidirectional Glenn at age six months. He is presently 23 months old and doing well. With careful consideration of the individual patient and comorbidities associated with JS, we propose that at least a subset of patients with JS and HLHS can do well with staged surgical palliation.

Hypoplastic Left Heart Syndrome: A New Paradigm for an Old Disease?

Hypoplastic left heart syndrome occurs in up to 3% of all infants born with congenital heart disease and is a leading cause of death in this population. Although there is strong evidence for a genetic component, a specific genetic cause is only known in a small subset of patients, consistent with a multifactorial etiology for the syndrome. There is controversy surrounding the mechanisms underlying the syndrome, which is likely due, in part, to the phenotypic variability of the disease. The most commonly held view is that the “decreased” growth of the left ventricle is due to a decreased flow during a critical period of ventricular development. Research has also been hindered by what has been, up until now, a lack of genetically engineered animal models that faithfully reproduce the human disease. There is a growing body of evidence, nonetheless, indicating that the hypoplasia of the left ventricle is due to a primary defect in ventricular development. In this review, we discuss the evidence demonstrating that, at least for a subset of cases, the chamber hypoplasia is the consequence of hyperplasia of the contained cardiomyocytes. In this regard, hypoplastic left heart syndrome could be viewed as a neonatal form of cardiomyopathy. We also discuss the role of the endocardium in the development of the ventricular hypoplasia, which may provide a mechanistic basis for how impaired flow to the developing ventricle leads to the anatomical changes seen in the syndrome.

Gene-targeted deletion in mice of the Ets-1 transcription factor, a candidate gene in the Jacobsen syndrome kidney "critical region," causes abnormal kidney development

Ets-1 is a member of the Ets family of transcription factors and has critical roles in multiple biological functions. Structural kidney defects occur at an increased frequency in Jacobsen syndrome (OMIM #147791), a rare chromosomal disorder caused by deletions in distal 11q, implicating at least one causal gene in distal 11q. In this study, we define an 8.1 Mb "critical region" for kidney defects in Jacobsen syndrome, which spans ~50 genes. We demonstrate that gene-targeted deletion of Ets-1 in mice results in some of the most common congenital kidney defects occurring in Jacobsen syndrome, including: duplicated kidney, hypoplastic kidney, and dilated renal pelvis and calyces. Taken together, our results implicate Ets-1 in normal mammalian kidney development and, potentially, in the pathogenesis of some of the most common types of human structural kidney defects.

Arterial Switch Operation in a Patient With Ehlers-Danlos Syndrome Type IV

Ehlers-Danlos syndrome vascular type IV is characterized by translucent skin, easy bruising, and fragility of arteries. A full-term female infant presented at four weeks of age with a diagnosis of d-transposition of the great arteries with restrictive atrial septal defect. She successfully underwent emergent balloon atrial septostomy and placement of patent ductus arteriosus (PDA) stent. She required restenting of the PDA and pulmonary artery banding prior to arterial switch procedure. At 16 months of age, the patient successfully underwent arterial switch procedure without complication. This report demonstrates the feasibility of an arterial switch operation along with long-term follow-up of this rare condition.

Utility of Genetic Testing in Elite Volleyball Players with Aortic Root Dilation

Basketball and volleyball attract individuals with a characteristic biophysical profile, mimicking features of Marfan syndrome. Consequently, identification of these abnormalities can be lifesaving.

PURPOSE

To determine how physical examination, echocardiography, and genetic screening can identify elite volleyball players with a previously undiagnosed aortopathy.

METHODS

We have performed cardiac screening on 90 US Volleyball National Team members and identified four individuals with dilated sinuses of Valsalva. This case series reports on three individuals who underwent a comprehensive genetics evaluation, including gene sequencing.

RESULTS

Cardiac screening combined with genetic testing can identify previously undiagnosed tall athletes with an aortopathy, in the absence of noncardiac findings of a connective tissue disorder. Subject 1 had a revised Ghent systems (RGS) score of 2 and a normal aortopathy gene panel. Subject 2 had a RGS score of 1 and genetic testing revealed a de novo disease causing mutation in the gene encoding fibrillin-1 (FBN1). Subject 3 had an RGS score of 4.0 and had a normal aortopathy gene panel.

CONCLUSIONS

Despite variable clinical features of Marfan syndrome, dilated sinuses of Valsalva were found in 4.9% of the athletes. A disease-causing mutation in the FBN1 gene was identified in subject 2, who had the lowest RGS but the largest aortic root measurement. Subjects 1 and 3, with the highest RGS, had a normal aortopathy gene panel. Our findings provide further evidence suggesting that a cardiac evaluation, including a screening echocardiogram, should be performed on all elite tall adult athletes independent of other physical findings. Genetic testing should be considered for athletes with dilated sinuses of Valsalva (male, >4.2 cm; female, >3.4 cm), regardless of other extracardiac findings.

Jacobsen syndrome: Advances in our knowledge of phenotype and genotype

In 1973, the Danish geneticist Petrea Jacobsen described a three-generation family in which the proband carried a presumed terminal deletion at the end of the long arm of chromosome 11 (11q). This patient had dysmorphic features, congenital heart disease, and intellectual disability. Since Dr. Jacobsen's initial report, over 200 patients with Jacobsen syndrome have been reported, suggesting that Jacobsen syndrome is a contiguous gene disorder. With the advent of high resolution deletion mapping and the completion of the human genome sequencing project, a comprehensive genotype/phenotype analysis for Jacobsen syndrome became possible. In this article, we review research describing individual causal genes in distal 11q that contribute to the overall Jacobsen syndrome clinical phenotype. Through a combination of human genetics and the use of genetically engineered animal models, causal genes have been identified for the clinical problems in JS that historically have caused the greatest morbidity and mortality: congenital heart disease, the Paris-Trousseau bleeding disorder, intellectual disability, autism, and immunodeficiency. Insights gained from these studies are being applied for future drug development and clinical trials, as well as for a potential strategy for the prevention of certain forms of congenital heart disease. The results of these studies will likely not only improve the prognostic and therapeutic approaches for patients with Jacobsen syndrome, but also for the general population afflicted with these problems.

Somatic mutations in NKX2–5, GATA4, and HAND1 are not a common cause of tetralogy of Fallot or hypoplastic left heart

The majority of congenital heart disease (CHD) occurs as a sporadic finding, with a minority of cases associated with a known genetic abnormality. Combinations of genetic and environmental factors are implicated, with the recent and intriguing hypothesis that an apparently high rate of somatic mutations might explain some sporadic CHD. We used samples of right ventricular myocardium from patients undergoing surgical repair of tetralogy of Fallot (TOF) and hypoplastic left heart (HLH) to examine the incidence of somatic mutation in cardiac tissue. TOF is a common form of cyanotic CHD, occurring in 3.3 per 10,000 live births. HLH is a rare defect in which the left side of the heart is severely under-developed. Both are severe malformations whose genetic etiology is largely unknown. We carried out direct sequence analysis of the NKX2–5 and GATA4 genes from fresh frozen cardiac tissues and matched blood samples of nine TOF patients. Analysis of NKX2–5, GATA4, and HAND1 was performed from cardiac tissue of 24 HLH patients and three matched blood samples. No somatic or germline mutations were identified in the TOF or HLH patients. Although limited by sample size, our study suggests that somatic mutations in NKX2–5 and GATA4 are not a common cause of isolated TOF or HLH.

Deletion of ETS-1, a gene in the Jacobsen syndrome critical region, causes ventricular septal defects and abnormal ventricular morphology in mice

Congenital heart defects comprise the most common form of major birth defects, affecting 0.7% of all newborn infants. Jacobsen syndrome (11q-) is a rare chromosomal disorder caused by deletions in distal 11q. We have previously determined that a wide spectrum of the most common congenital heart defects occur in 11q-, including an unprecedented high frequency of hypoplastic left heart syndrome (HLHS). We identified an approximately 7 Mb 'cardiac critical region' in distal 11q that contains a putative causative gene(s) for congenital heart disease. In this study, we utilized chromosomal microarray mapping to characterize three patients with 11q- and congenital heart defects that carry interstitial deletions overlapping the 7 Mb cardiac critical region. We propose that this 1.2 Mb region of overlap harbors a gene(s) that causes at least a subset of the congenital heart defects that occur in 11q-. We demonstrate that one gene in this region, ETS-1 (a member of the ETS family of transcription factors), is expressed in the endocardium and neural crest during early mouse heart development. Gene-targeted deletion of ETS-1 in mice in a C57/B6 background causes, with high penetrance, large membranous ventricular septal defects and a bifid cardiac apex, and less frequently a non-apex-forming left ventricle (one of the hallmarks of HLHS). Our results implicate an important role for the ETS-1 transcription factor in mammalian heart development and should provide important insights into some of the most common forms of congenital heart disease.

Deletion of JAM-C, a candidate gene for heart defects in Jacobsen syndrome, results in a normal cardiac phenotype in mice

The 11q terminal deletion disorder (11q-) is a rare chromosomal disorder caused by a deletion in distal 11q. Fifty-six percent of patients have clinically significant congenital heart defects. A cardiac "critical region" has been identified in distal 11q that contains over 40 annotated genes. In this study, we identify the distal breakpoint of a patient with a paracentric inversion in distal 11q who had hypoplastic left heart and congenital thrombocytopenia. The distal breakpoint mapped to JAM-3, a gene previously identified as a candidate gene for causing HLHS in 11q-. To determine the role of JAM-3 in cardiac development, we performed a comprehensive cardiac phenotypic assessment in which the mouse homolog for JAM-3, JAM-C, has been deleted. These mice have normal cardiac structure and function, indicating that haplo-insufficiency of JAM-3 is unlikely to cause the congenital heart defects that occur in 11q- patients. Notably, we identified a previously undescribed phenotype, jitteriness, in most of the sick or dying adult JAM-C knockout mice. These data provide further insights into the identification of the putative disease-causing cardiac gene(s) in distal 11q, as well as the functions of JAM-C in normal organ development.

Jacobsen syndrome

Jacobsen syndrome is a MCA/MR contiguous gene syndrome caused by partial deletion of the long arm of chromosome 11. To date, over 200 cases have been reported. The prevalence has been estimated at 1/100,000 births, with a female/male ratio 2:1. The most common clinical features include pre- and postnatal physical growth retardation, psychomotor retardation, and characteristic facial dysmorphism (skull deformities, hypertelorism, ptosis, coloboma, downslanting palpebral fissures, epicanthal folds, broad nasal bridge, short nose, v-shaped mouth, small ears, low set posteriorly rotated ears). Abnormal platelet function, thrombocytopenia or pancytopenia are usually present at birth. Patients commonly have malformations of the heart, kidney, gastrointestinal tract, genitalia, central nervous system and skeleton. Ocular, hearing, immunological and hormonal problems may be also present. The deletion size ranges from approximately 7 to 20 Mb, with the proximal breakpoint within or telomeric to subband 11q23.3 and the deletion extending usually to the telomere. The deletion is de novo in 85% of reported cases, and in 15% of cases it results from an unbalanced segregation of a familial balanced translocation or from other chromosome rearrangements. In a minority of cases the breakpoint is at the FRA11B fragile site. Diagnosis is based on clinical findings (intellectual deficit, facial dysmorphic features and thrombocytopenia) and confirmed by cytogenetics analysis. Differential diagnoses include Turner and Noonan syndromes, and acquired thrombocytopenia due to sepsis. Prenatal diagnosis of 11q deletion is possible by amniocentesis or chorionic villus sampling and cytogenetic analysis. Management is multi-disciplinary and requires evaluation by general pediatrician, pediatric cardiologist, neurologist, ophthalmologist. Auditory tests, blood tests, endocrine and immunological assessment and follow-up should be offered to all patients. Cardiac malformations can be very severe and require heart surgery in the neonatal period. Newborns with Jacobsen syndrome may have difficulties in feeding and tube feeding may be necessary. Special attention should be devoted due to hematological problems. About 20% of children die during the first two years of life, most commonly related to complications from congenital heart disease, and less commonly from bleeding. For patients who survive the neonatal period and infancy, the life expectancy remains unknown.

Autosomal dominant inheritance of left ventricular outflow tract obstruction

Most nonsyndromic congenital heart malformations (CHMs) in humans are multifactorial in origin, although an increasing number of monogenic cases have been reported recently. We describe here four new families with presumed autosomal dominant inheritance of left ventricular outflow tract obstruction (LVOTO), consisting of hypoplastic left heart (HLHS) or left ventricle (HLV), aortic valve stenosis (AS) and bicuspid aortic valve (BAV), hypoplastic aortic arch (HAA), and coarctation of the aorta (CoA). LVOTO in these families shows a wide clinical spectrum with some family members having severe anomalies such as hypoplastic left heart, and others only minor anomalies such as mild aortic valve stenosis. This supports the suggestion that all anomalies of the LVOTO spectrum are developmentally related and can be caused by a single gene defect.

Endocrine abnormalities in patients with Jacobsen (11q-) syndrome

Jacobsen syndrome (JS), a rare disorder with multiple dysmorphic features, is caused by the terminal deletion of chromosome 11q. Short stature has been reported in this syndrome, however very few of these patients have undergone endocrine evaluation. Serum insulin-like growth factor-1 (IGF-1) levels are an indirect indicator of growth hormone activity and are a useful initial screening tool in the assessment of an individual's growth hormone axis. We studied nine children with JS, eight of whom had short stature. Four out of eight children with short stature (50%) had low IGF-1 values, with three low for age and one low for Tanner stage. Four out of six males (67%) had cryptorchidism, a potential sign of hypogonadism. We conclude that low IGF-1 is common in patients with JS and short stature, and that growth hormone status and possibly hypothalamic-pituitary function should be evaluated in this patient population.

Paris-Trousseau syndrome : clinical, hematological, molecular data of ten new cases

Paris-Trousseau syndrome (PTS) is an inherited disorder characterized by mild hemorragic tendency associated with 11q chromosome deletion. Here we report ten new patients (5 boys, 5 girls) with complete clinical history, biological data, ultra-structural and molecular investigations. Thrombocytopenia is chronic in all the patients except two boys in whom it disappeared during the two first years of life. On Romanovsky stained peripheral blood smears, abnormal platelets with giant granules were detected in all the children and confirmed by electron microscopy (EM). On bone marrow smears, dysmegakaryopoiesis with many micromegakaryocytes was constantly observed. Abnormal alpha-granules were virtually absent from bone marrow and cultured megakaryocytes, while EM detected numerous images of granule fusion within blood platelets. Molecular analyses evidenced that the fli-1 gene is deleted in all the patients except one confirming the crucial role of the transcription factor FLI-1 in megakaryopoiesis. In summary, this study documents ten new cases of PTS with characteristic alpha-granule abnormalities, and shows the putative pathogenic role of fli-1 gene in the pathophysiology of this syndrome.

Cardiac homeobox gene NKX2-5 mutations and congenital heart disease: associations with atrial septal defect and hypoplastic left heart syndrome

OBJECTIVES

We sought to examine the importance of mutations in the cardiac transcription factor gene NKX2-5 in patients with an atrial septal defect (ASD), patent foramen ovale (PFO), or hypoplastic left heart syndrome (HLHS).

BACKGROUND

Mutations in NKX2-5 have been found in families showing secundum ASD and atrioventricular (AV) conduction block and in some individuals with tetralogy of Fallot. The prevalence of NKX2-5 mutations in sporadic cases of ASD/PFO and other forms of congenital heart disease is unknown.

METHODS

A cohort of 146 individuals with secundum ASD, PFO complicated by paradoxical embolism, or HLHS were evaluated. Patients with ASD or PFO were ascertained irrespective of family history or associated cardiac abnormalities. The coding region of the NKX2-5 locus was amplified by polymerase chain reaction and sequenced.

RESULTS

Among 102 ASD and 25 PFO patients screened, 13 patients (10%) had a positive family history and 5 patients (4%) had AV conduction block. We found one previously documented NKX2-5 missense mutation, T178M, in members of a family with ASD without AV conduction block. One NKX2-5 mutation-positive child from this family had HLHS, although no mutations were subsequently found in 18 patients with sporadic or familial HLHS. In a second ASD family without AV conduction block, we found a missense change, E21Q, previously reported as pathogenic. Because this change did not segregate with disease status, we propose that it is a non-disease-causing polymorphism.

CONCLUSIONS

Our findings suggest that NKX2-5 mutations are a relatively infrequent cause of sporadic ASD and HLHS. Screening for NKX2-5 mutations may be warranted in individuals with ASD and a positive family history, irrespective of the presence or absence of AV conduction block.

Maternal psychological impact of fetal echocardiography

The maternal psychological impact of fetal echocardiography may be deleterious in the face of newly diagnosed congenital heart disease. This questionnaire-based study prospectively examined the psychological impact of both normal and abnormal fetal echocardiography. Normal fetal echocardiography decreased maternal anxiety, increased happiness, and increased the closeness women felt toward their unborn children. In contrast, when fetal echocardiography detected congenital heart disease, maternal anxiety typically increased, and mothers commonly felt less happy about being pregnant. However, among women who had recently delivered infants with congenital heart disease, those who had had fetal echocardiography during the pregnancy felt less responsible for their infants' defects and tended to have improved their relationships with the infants' fathers after the prenatal diagnosis of congenital heart disease. Further study of the psychological and medical impact of fetal echocardiography will be necessary to define and optimize the clinical value of this powerful diagnostic tool.

Fli-1 is required for murine vascular and megakaryocytic development and is hemizygously deleted in patients with thrombocytopenia

The ETS gene Fli-1 is involved in the induction of erythroleukemia in mice by Friend murine leukemia virus and Ewings sarcoma in children. Mice with a targeted null mutation in the Fli-1 locus die at day 11.5 of embryogenesis with loss of vascular integrity leading to bleeding within the vascular plexus of the cerebral meninges and specific downregulation of Tek/Tie-2, the receptor for angiopoietin-1. We also show that dysmegakaryopoiesis in Fli-1 null embryos resembles that frequently seen in patients with terminal deletions of 11q (Jacobsen or Paris-Trousseau Syndrome). We map the megakaryocytic defects in 14 Jacobsen patients to a minimal region on 11q that includes the Fli-1 gene and suggest that dysmegakaryopoiesis in these patients may be caused by hemizygous loss of Fli-1.

Co-localisation of CCG repeats and chromosome deletion breakpoints in Jacobsen syndrome: evidence for a common mechanism of chromosome breakage

Folate-sensitive fragile sites are associated with the expansion and hypermethylation of CCG-repeats. The fragile site in 11q23.3, FRA11B, has been shown to cause chromosome deletions in vivo, its expression being associated with Jacobsen (11q-) syndrome. However, the majority of Jacobsen deletions are distal to FRA11B and are not related to its expression. To test the hypothesis that other unidentified fragile sites might be located in 11q23.3-24 and may cause these deletions, we have identified and characterised CCG-trinucleotide repeats within a 40 Mb YAC contig spanning distal chromosome 11q. Only eight CCG-repeats were identified within the entire YAC contig (not including FRA11B ), six of which map to the region of 11q23.3-24 that includes Jacobsen deletions. We have previously collated the deletion mapping data of 24 Jacobsen patients with the physical map of chromosome 11q, and accurately localised six breakpoints to short intervals corresponding to individual YAC clones. We now show that in each of these cases, YAC clones found to contain a deletion breakpoint also contain a CCG-repeat. The improved analysis of one of these deletions, together with those of several new Jacobsen cases, further strengthens this association by localising five breakpoints to individual PAC clones containing CCG-repeats. These data provide strong evidence for the non-random clustering of chromosome deletion breakpoints with CCG-repeats, and suggests that they may play an important role in a common mechanism of chromosome breakage.