Outflow Tract Abnormalities Research Articles

Cardiac Neural Crest Cells: Their Rhombomeric Specification, Migration, and Association with Heart and Great Vessel Anomalies.

Outflow tract abnormalities are the most frequent congenital heart defects. These are due to the absence or dysfunction of the two main cell types, i.e., neural crest cells and secondary heart field cells that migrate in opposite directions at the same stage of development. These cells directly govern aortic arch patterning and development, ascending aorta dilatation, semi-valvular and coronary artery development, aortopulmonary septation abnormalities, persistence of the ductus arteriosus, trunk and proximal pulmonary arteries, sub-valvular conal ventricular septal/rotational defects, and non-compaction of the left ventricle. In some cases, depending on the functional defects of these cells, additional malformations are found in the expected spatial migratory area of the cells, namely in the pharyngeal arch derivatives and cervico-facial structures. Associated non-cardiovascular anomalies are often underestimated, since the multipotency and functional alteration of these cells can result in the modification of multiple neural, epidermal, and cervical structures at different levels. In most cases, patients do not display the full phenotype of abnormalities, but congenital cardiac defects involving the ventricular outflow tract, ascending aorta, aortic arch and supra-aortic trunks should be considered as markers for possible impaired function of these cells. Neural crest cells should not be considered as a unique cell population but on the basis of their cervical rhombomere origins R3-R5 or R6-R7-R8 and specific migration patterns: R3-R4 towards arch II, R5-R6 arch III and R7-R8 arch IV and VI. A better understanding of their development may lead to the discovery of unknown associated abnormalities, thereby enabling potential improvements to be made to the therapeutic approach.

Assessment of Atrioventricular Septal Defect on Echocardiography

Atrioventricular septal defect comprise of 1.4-2.9% of congenital cardiac defect and is most common congenital cardiac defect in Trisomy 21. This anomaly is characterized by a common atrioventricular junction coexisting with atrial and/or ventricular septal defect, cleft of left atrioventriocular valve along with left ventricular outflow tract abnormality. Due to cleft of left atrioventricular valve, valve regurgitation is almost invariably present leading to early onset of congestive cardiac failure in these patients. Other associated structural heart defects are pulmonary stenosis, ductal arteriosus, aortic arch anomalies, pulmonary and systemic venous anomalies and unbalaned atrioventricular valve connection leading to univentricular physiology. Echocardiography plays very crucial role in defning the anomaly and planning management In this article, I am going to focus on role of echocardiography in atrioventricular septal defect.

Prevalence of right ventricular outflow tract abnormalities among recipients in twin-twin transfusion syndrome after fetoscopic laser surgery in 90 consecutive cases.

Right ventricular outflow tract obstruction (RVOTO) is a severe complication in recipients in twin-twin transfusion syndrome (TTTS). This study investigated the prevalence of RVOTO in TTTS after laser surgery and examined the risk factors for RVOTO. This retrospective study evaluated 90 patients who had undergone laser surgery and been followed for 6months after birth. The diagnosis of RVOTO was made based on postnatal echocardiography findings. Ultrasound and clinical records, including maternal and neonatal data, were retrieved from our database. Risk factors for developing RVOTO were compared between recipients with and without RVOTO in a statistical analysis. Six surviving recipients were diagnosed with RVOTO. Three recipients had developed severe pulmonary stenosis (PS) that required percutaneous transluminal pulmonary valvuloplasty or balloon pulmonary angioplasty. A total of 6.7% of recipients (6/90) had RVOTO, consisting of PS and tricuspid regurgitation (TR), and 3.3% of recipients (3/90) required invasive treatment. The characteristic factors did not differ significantly between recipients with and without RVOTO. This study revealed that 6.7% of recipients with TTTS had PS, and 3.3% required invasive treatment for PS. However, no significant association was noted between RVOTO development in recipients and maternal clinical data and fetal ultrasound examination findings. It is difficult to predict RVOTO development in recipients using only preoperative ultrasound and clinical information.

EP25.04: Prevalence of recipients' right ventricular outflow tract abnormalities in Twin–twin transfusion syndrome after fetoscopic laser surgery

EP25.04: Prevalence of recipients' right ventricular outflow tract abnormalities in Twin–twin transfusion syndrome after fetoscopic laser surgery

Congenital Cardiac Outflow Tract Abnormalities in Dogs: Prevalence and Pattern of Inheritance From 2008 to 2017.

Subvalvular aortic stenosis (SAS) and valvular pulmonic stenosis (PS) are two of the most common congenital heart diseases of dogs. The aim of this study was to determine the prevalence and mode of inheritance of these congenital heart diseases in a large veterinary teaching hospital population. Case records of dogs presented to the University of California Davis, Veterinary Medical Teaching Hospital (UCD VMTH) between January 2008 to December 2017 were reviewed retrospectively and pedigree information was obtained when available. There were 259 unique SAS and 336 unique PS cases diagnosed during the study period. The prevalence of SAS was 0.3% of overall hospital admissions and 4.7% for all dogs seen by the cardiology service. The prevalence for PS was 0.41% of overall hospital admissions and 6.1% of dogs seen by the cardiology service. Bullmastiffs and Newfoundlands had the greatest prevalence (6.59 and 4.46%, respectively) and odds ratio (52.43 and 34.73, respectively) for SAS. Bulldogs and French Bulldogs had the greatest prevalence (4.8 and 2.7%, respectively) and odds ratio (13.32 and 7.52, respectively) for PS. The identified prevalence of SAS and PS is higher than previously reported. Pedigree analysis in SAS affected Bullmastiffs, Golden Retrievers, and Rottweilers suggested an autosomal recessive pattern of inheritance. The mode of inheritance for PS in Bulldogs, also appears to be autosomal recessive. The results of this study can be used to inform future selection of breeding pairs and genetic studies aimed at reducing the prevalence of these common congenital heart diseases.

Quantile Score: A New Reference System for Quantitative Fetal Echocardiography Based on a Large Multicenter Study

Normative ranges of fetal echocardiographic measurements are important for quantitative diagnosis of fetal cardiovascular disease. The current normative ranges were derived from small samples and were based on the hypothesis of a normal distribution of these measurements during fetal cardiovascular growth. The aims of this study were to test the hypothesis of a normal distribution of fetal echocardiographic measurements in a large multicenter cohort and to propose a reference system without the normal distribution hypothesis to improve accuracy of fetal echocardiographic measurements. Fifty-two variables from 6,343 normal fetal echocardiographic examinations were acquired from seven Chinese centers. The hypothesis of a normal distribution used in ordinary least squares regression was tested with the Jarque-Bera test. The quantile score (q score) derived from quantile regression without normal distribution hypothesis was compared with the Z score derived from ordinary least squares regression. A total of 288 fetuses with outflow tract and great artery abnormalities and 300 normal fetuses were used to compare the diagnostic accuracy of q and Z scores. All fetal echocardiographic measurements showed non-normal distributions (P<.001). The normal range was underestimated by ordinary least squares regression compared with quantile regression by 30±11%. The partial normalized areas under the receiver operating characteristic curve within the 20% false-positive rate were 0.62 and 0.50 for the q and Z scores, respectively. The q score provides a more robust system for determining normative ranges of fetal echocardiographic measurements. The improved sensitivity of matched false-positive rates makes the q score a more accurate reference for prenatal diagnosis, assessment, and prognosis of fetal cardiovascular disease.

Abstract 16895: Lrp1, an Endocytic Vesicle Trafficking Protein, is Associated With Congenital Heart Diseases - Through a "non-Autonomous" Action

Backgrounds: Congenital heart diseases affect nearly 1% of neonates per year in the United States and are the leading cause of neonatal death. Despite a strong indication of genetic contribution to congenital heart diseases, the developmental processes and genetic components are poorly understood. From the large-scale forward genetic screen using inbred mice chemically mutagenized with ethyl-nitrosourea (ENU), a novel finding of endocytic trafficking gene mutations, including Lrp1, were recovered as causing congenital heart disease phenotypes. Endocytosis plays roles in modulating cell signaling by regulating the trafficking of the internalized endocytic vesicles to different endosomal compartments, some destined for fusion with lysosomes and degradation while others are recycled to the surface by recycling endosomes. Mutations in these genes causes a spectrum of congenital heart disease comprising of outflow tract abnormalities and alignment defects. Methods and Results: The LRP1 [line 1554(MGI 96828)] mutant mouse line recovered from a forward genetic screen results from a missense (C4232R) mutation in the region encoding the epidermal growth factor (EGF) repeat domain of LRP1. The mutants exhibit a spectrum of septation and outflow tract defects including endocardial cushion defects, double outlet of right ventricle with normal related great arteries as well as DORV with D-malposition of great arteries (Taussig-Bing anomalies). Mouse embryonic fibroblasts (MEF) from LRP1 m/m mutants demonstrated decreased cell-surface expression and increased retention in the endosomes. Migration assay of MEF demonstrated decreased migration of LRP1 m/m compared with control with normal Golgi orientation. The decreasing migration LRP1 m/m also observed in the endocardial cushion tissue from E9.5-10.5 embryos. Different cell lineages crucial to cardiac development with tissue-specific genetic manipulations were used to define the roles of the LRP1 pathway in these three fields of cells during outflow tract development and septation. Cardiac neural crest cell (Wnt1-Cre) knockout of LRP1 recapitulate LRP1 m/m cardiac phenotypes as well as Nkx2.5/Tie2-cre double knockout of LRP1. RNA expression profile suggests Notch pathway and integrin pathway are associated with LRP1 during cardiac development. Conclusions: We provide the first evidence of endocytic vesicle trafficking pathway associated with the development of congenital heart diseases with malalignment/septation and outflow tract defects

Modeling Cardiac Hemodynamic Response During Exercise in Health and Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract and tissue abnormalities. Exercise testing has become an integral and powerful tool for the noninvasive evaluation of HCM and, in some patients, it could define a treatment strategy. Obiective: To model the hemodynamic alterations during exercise in healthy and HCM patients, obtained by noninvasive methods. Cardiac output (CO), heart rate (HR), arterial blood pressure (ABP) and Total Peripheral Resistance (TPR) were assessed during exercise. The evaluation included a curve-fitting approach (sigmoidal model) that allowed a quantitative comparison of CO profiles. When compared to controls, patients with HCM showed reduced peak exercise cardiac output and demonstrated high peripheral resistance during exercise. Analysis of modeled it CO curves revealed a higher maximum rate of recovery in healthy individuals than in HCM patients. The application of the sigmoidal model showed to be efficient in the characterization of CO dynamics for the different studied groups.

Anesthesia for Percutaneous Pulmonary Valve Implantation: A Case Series

Twenty percent of patients born with congenital heart disease present with right ventricular outflow tract abnormalities. These patients require multiple surgical procedures in their lifetime. Transcatheter pulmonary valve replacement (TPVR) has become a viable alternative to conventional pulmonary valve and right ventricular outflow tract surgery in pediatric and adult populations. In this retrospective review, we analyze the perioperative management of adult patients who underwent TPVR in our center. The study consisted of a chart review of patients who underwent TPVR at Toronto General Hospital between 2006 and 2015. Information about preoperative assessment, intraoperative anesthetic management, and intra- and postprocedural complications was collected. Two types of percutaneous valves have been used for a conduit or valve size between 16 and 28 mm. These procedures are done via the femoral, jugular, or subclavian vein under general anesthesia. Seventy-nine adults (17-68 years of age) who underwent elective TPVR procedures were included. General anesthesia was used in all cases. Defibrillation was necessary in 1 case, and bradycardia was spontaneously resolved in another 1. Eighty-five percent were successfully extubated at the end of the procedure. Five patients required intraoperative inotropic support. Three patients presented self-resolved hemoptysis. Mechanical ventilation for >24 hours was necessary in 3 cases, 2 of which also required concomitant inotropic support. Four failed deployments and 1 case of persistent conduit stenosis were reported. Three patients required reintubation. All patients were discharged home. Patients undergoing TPVR represent a complex and heterogeneous population. General anesthesia with endotracheal intubation is preferred. Setup for urgent lung isolation and cardiac defibrillation should be considered. Postoperative monitoring and intensive care setting are required. Anesthesiologists with cardiac anesthesia training are probably better suited to manage these patients.

Repair for Congenital Mitral Valve Stenosis.

We report the techniques and long-term outcome of mitral valve (MV) repair to correct congenital mitral stenosis in children. Between 1986 and 2014, 137 children (mean age 4.1 ± 5.0, range 1 month-16.8 years) underwent repair of congenital mitral stenosis (CMS). In 48 patients, CMS is involved in Shone's anomaly. The typical congenital MS (type I) was seen in 56 patients. Hypoplastic MV (type II, n = 15) was associated with severe left ventricular outflow tract abnormalities and hypoplastic left ventricular cavity and muscle mass. Supravalvar ring (type III, n = 48) ranged from a thin membrane to a thick discrete fibrous ridge. Parachute MV (type IV, n = 10) have 2 leaflets and barely distinguishable commissures, but all chordae merged either into 1 major papillary muscle or asymmetric papillary muscles-1 dominant and the other minuscule. Hammock valve (type IV, n = 8) appeared dysplastic with shortened chordae directly inserted into the posterior left ventricular muscle mass. MV repair was performed using commissurotomy, chordal division, papillary muscle splitting and fenestration, and mitral ring resection, each applied according to the presenting morphology. During the 28-year follow-up period, 23 patients underwent repeat MV repair and 3 underwent MV replacement after failed attempts at repeat repair. At 1 and 15 years postoperatively, freedom from reoperation was 89.3 ± 5.1% and 52.8 ± 11.8%, and cumulative survival rates were 92.3 ± 4.3% and 70.3 ± 8.9, respectively. Mortality unrelated to repair accounted for 9 (20%) deaths. Long-term functional outcome of MV repair in children with CMS is satisfactory. Repeat repair or replacement may be deemed necessary during the course of follow-up.

Abstract 24031: Machine Learning Detection of Obstructive Hypertrophic Cardiomyopathy Using a Wearable Biosensor

Introduction: Hypertrophic cardiomyopathy (HCM) is a heart muscle disease characterized by left ventricular (LV) hypertrophy without a systemic etiology and is associated with heart failure, stroke and sudden death. Disease prevalence is estimated at 1:500, but ~84% remain undiagnosed. Patients with obstructive HCM (oHCM) have dynamic obstruction of the LV outflow tract and characteristic abnormalities in arterial bloodflow patterns. Hypothesis: Arterial pulsewaves recorded with a wearable biosensor and analyzed with machine learning algorithms could identify a signature of oHCM when compared to unaffected controls. Methods: We compared baseline arterial pulse wave morphology, obtained by photoplethysmography using an investigational wristworn biosensor (Wavelet Health, Mtn. View, CA), from oHCM patients enrolled in a digital health substudy of PIONEER HCM (NCT02842242) to unaffected controls from a Wavelet Health database. Five minute recordings were obtained at rest, and data sets were divided into training and validation cohorts. A beat-by-beat machine learning model was developed using a predefined feature set to calculate an HCM probability score, and an optimal threshold score was determined. The model was evaluated using summary statistics and an ROC area-under-curve metric. Results: Arterial pulsewave recordings were obtained from 14 patients with oHCM at rest and 81 unaffected controls. An oHCM machine learning classifier was developed based on 42 calculated metrics. After training and cross-validation (n=9 oHCM, n=48 control), the model achieved 98% accuracy. Application of this model to a validation cohort (n=5 oHCM, n=33 control) confirmed an increased probability in oHCM patients compared to unaffected controls (0.40 ± 0.13 vs. 0.18 ± 0.10; p=0.006). Analysis of the ROC curve in the pooled cohort shows an area under the curve of 0.88. Conclusion: This first-of-its-kind study suggests that a signature of arterial bloodflow in oHCM can be identified with the combination of a wristworn biosensor and machine learning algorithms. These data raise the possibility of a novel approach to the non-invasive detection of oHCM.

The HAND1 frameshift A126FS mutation does not cause hypoplastic left heart syndrome in mice.

To test if a human Hand1 frame shift mutation identified in human samples is causative of hypoplastic left heart syndrome (HLHS). HLHS is a poorly understood single ventricle congenital heart defect that affects two to three infants in every 10 000 live births. The aetiologies of HLHS are largely unknown. The basic helix-loop-helix transcription factor HAND1 is required for normal heart development. Interrogation of HAND1 sequence from fixed HLHS tissues identified a somatic frame-shift mutation at Alanine 126 (NP_004812.1 p.Ala126Profs13X defined as Hand1A126fs). Hand1A126fs creates a truncated HAND1 protein that predictively functions as dominant negative. To determine if this mutation is causative of HLHS, we engineered a conditional Hand1A126fs mouse allele. Activation of this allele with Nkx2.5Cre results in E14.5 lethality accompanied by cardiac outflow tract and intraventricular septum abnormalities. Using αMHC-Cre or Mef2CAHF-Cre to activate Hand1A126fs results in reduced phenotype and limited viability. Left ventricles of Hand1A126FS mutant mice are not hypoplastic. Somatically acquired Hand1A126FS mutation is not causative of HLHS. Hand1A126FS mutation does exhibit embryonic lethal cardiac defects that reflect a dominant negative function supporting the critical role of Hand1 in cardiogenesis.

Circulating mRNA in Maternal Plasma at the Second Trimester of Pregnancy: A Possible Screening Tool for Cardiac Conotruncal and Left Ventricular Outflow Tract Abnormalities.

Maternal plasma is a source of circulating placental nucleic acids. This study was designed to detect aberrantly expressed placental mRNA genes circulating in the maternal plasma of pregnancies affected with fetal conotruncal anomalies (CNTRA) and left-ventricular outflow tract (LVOT) obstruction in the second trimester of pregnancy. This was a retrospective monocentric study conducted from 1 Jan 2016 to 31 Dec 2016. NanoString technology was used to identify aberrantly expressed genes, comparing 36 women carrying a fetus with CNTRA or LVOT obstruction to 42 controls at 19-24 weeks of gestation. The genes with differential expression were subsequently tested using real-time polymerase chain reaction. Linear discriminant analysis was used to combine all the mRNA species with discriminant ability for CNTRA and LVOT obstruction. A multivariable receiver operating characteristic (ROC) curve having the estimated discriminant score as an explanatory variable was generated for the two affected groups versus controls. Three genes with differential expression, namely MAPK1, IQGAP1 and Visfatin were found. The ROC curves yielded detection rates of 60 and 62.5% at a false-positive rate of 5% for CNTRA and LVOT, respectively. These data suggested that molecular screening of CNTRA and LVOT obstruction in the second trimester is feasible. Prospective studies are needed to test the discriminant ability of these genes and to calculate the predictive positive value in the general population.

Outflow Tract Abnormalities: Overview

Outflow Tract Abnormalities: Overview

Notch-dependent EMT is attenuated in patients with aortic aneurysm and bicuspid aortic valve

Bicuspid aortic valve is the most common congenital heart malformation and the reasons for the aortopathies associated with bicuspid aortic valve remain unclear. NOTCH1 mutations are associated with bicuspid aortic valve and have been found in individuals with various left ventricular outflow tract abnormalities. Notch is a key signaling during cardiac valve formation that promotes the endothelial-to-mesenchymal transition. We address the role of Notch signaling in human aortic endothelial cells from patients with bicuspid aortic valve and aortic aneurysm. Aortic endothelial cells were isolated from tissue fragments of bicuspid aortic valve-associated thoracic aortic aneurysm patients and from healthy donors. Endothelial-to-mesenchymal transition was induced by activation of Notch signaling. Effectiveness of the transition was estimated by loss of endothelial and gain of mesenchymal markers by immunocytochemistry and qPCR. We show that aortic endothelial cells from the patients with aortic aneurysm and bicuspid aortic valve have down regulated Notch signaling and fail to activate Notch-dependent endothelial-to-mesenchymal transition in response to its stimulation by different Notch ligands. Our findings support the idea that bicuspid aortic valve and associated aortic aneurysm is associated with dysregulation of the entire Notch signaling pathway independently on the specific gene mutation.

4D flow MRI and T1 -Mapping: Assessment of altered cardiac hemodynamics and extracellular volume fraction in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is associated with altered hemodynamics in the left ventricular outflow tract (LVOT) and myocardial tissue abnormalities such as fibrosis. The aim of this study was to quantify changes in LVOT 3D hemodynamics and myocardial extracellular volume fraction (ECV, measure of fibrosis) and to investigate relationships between elevated flow metrics and left ventricular (LV) tissue abnormalities. Cardiac magnetic resonance imaging (MRI) including 4D flow (field strength = 1.5T, resolution = 2.1-4.0 × 2.1-4.0 × 2.5-3.2 mm(3) ; venc = 150-250 cm/s; TE/TR/FA = 2.2-2.5msec/4.6-4.9msec/15°) for the in vivo assessment of 3D blood flow velocities with full coverage of the LVOT was applied in 35 patients with HCM (54 ± 15 years) and 10 age-matched healthy controls (45 ± 14 years). In addition, pre- and postcontrast myocardial T1 -mapping (resolution = 2.3 × 1.8 mm, slice thickness = 8 mm, TE/TR-FA = 1.0-1.1msec/2.0-2.2msec/35°) of the LV (basal, mid-ventricular, apical short axis) was performed in a subgroup of 23 HCM patients. Analysis included the segmentation of the LVOT and quantification of peak systolic LVOT pressure gradients and rate of viscous energy loss EL ' as well as left ventricular ECV. HCM patients demonstrated significantly elevated peak systolic LVOT pressure gradients (21 ± 16 mmHg vs. 9 ± 2 mmHg) and energy loss EL ' (3.8 ± 2.5 mW vs. 1.5 ± 0.7 mW, P < 0.005) compared to controls. There was a significant relationship between increased LV fibrosis (ECV) with both elevated pressure gradients (R(2) = 0.44, P < 0.001) and energy loss EL ' (R(2) = 0.46, P < 0.001). The integration of 4D-flow and T1 -mapping-MRI allowed for the evaluation of tissue and flow abnormalities in HCM patients. Our findings suggest a mechanistic link between abnormal LVOT flow, increased LV loading, and adverse myocardial remodeling in HCM.

The Ross, Konno, and Ross-Konno operations for congenital left ventricular outflow tract abnormalities.

Operations for left ventricular outflow tract abnormalities are centred on hemodynamic conditions that relate to subvalvar stenosis, valvar stenosis/regurgitation, aortic annular hypoplasia, and supravalvar aortic stenosis. Operative interventions over the years have evolved because the intervening outcomes proved to be unsatisfactory. The resection for subvalvar aortic stenosis has progressed from a fibrous "membrane" resection to a more extensive fibromuscular resection. Operative solutions for valvar aortic stenosis and regurgitation have resulted in operative interventions that depend on simple commissurotomy, leaflet extensions, prosthetic mechanical valve replacement, biologic valve replacement, including the pulmonary autograft, and operations to treat aortic annular stenosis. Although there are enthusiastic proponents for all of these strategies, the fact remains that none have proven to be curative; patients can expect to undergo further procedures during their lifetimes. The short- and mid-term solutions to these left ventricular outflow tract abnormalities have improved based on operations that have been attended by increasing operative complexity. The purpose of this review is to chronicle the operative steps of the Ross operation, the Konno-Rastan operation, the modified Konno operation, the Ross-Konno operation, and the modified Ross-Konno operation.

Management of congenital lacrimal (anlage) fistula

Background/aimsTo review management choices and outcomes for congenital lacrimal (anlage duct) fistulae performed by a single ophthalmologist over a 10-year interval.MethodsAll cases of congenital lacrimal fistulae with minimum follow-up of...

Abstract 18574: Examination of a Highly Penetrant Mouse Model of Bicuspid Aortic Valve Demonstrates that Endothelial Notch1 is Required for Proper Morphogenesis of the Aortic Valve

Bicuspid aortic valve (BAV) is the most common type of cardiac malformation with an estimated prevalence of 1-2% in the population. BAV results in significant morbidity as it is one of the leading causes of valve stenosis and regurgitation in adults. We previously reported that mutations in the signaling and transcriptional regulator, NOTCH1 , were a cause of BAV in non-syndromic autosomal-dominant human pedigrees. The Notch signaling pathway is critical for multiple cell differentiation processes, and Notch1 is expressed in the developing and adult aortic valve. Recently, we have generated a new highly penetrant mouse model of aortic valve malformations using Notch1 haploinsufficient mice that are backcrossed in a Nos3-null background. Notch1 and Nos3 compound mutant adult mice ( Notch1 +/- ;Nos3 -/- ) display a nearly 100% incidence of BAV. The aortic valves of adult mutant mice are thickened and have associated stenosis and regurgitation. We have also found that by postnatal day 10, compound mutant mice suffer ~50% lethality compared to NOS3 -/- littermates. Here, we have examined Notch1 +/- ;Nos3 -/- embryos at serial timepoints to elucidate the mechanisms underlying BAV. Examination at embryonic day 18.5 (E18.5) demonstrated normal Mendelian ratios and histologic examination revealed thickened, malformed valve leaflets accompanied by other outflow tract abnormalities in NOS3 -/- ;Notch1 -/+ mice, likely contributing to the neonatal lethality. Further investigation at E13.5 and E15.5 indicated that the NOS3 -/- ;Notch1 -/+ aortic valve leaflets were significantly thicker than controls, suggesting that outflow tract cushion formation and early remodeling may be affected. In addition, we have generated mice are null for Nos3 and haploinsufficient for Notch1 in endothelial-derived cells using mice harboring a Notch1 -floxed allele and Tie2-Cre mice. Our preliminary results indicate that NOS3 -/- ; Notch1 fl/+ ;Tie2Cre + mice recapitulate the NOS3 -/- ;Notch1 -/+ cardiac phenotype and suggest that endothelial Notch1 is required for proper development of the aortic valve. Overall our data indicate that loss of endothelial Notch1 results in abnormal remodeling of the outflow tract cushions and contributes to BAV.

A human de novo mutation inMYH10phenocopies the loss of function mutation in mice

We used whole exome sequence analysis to investigate a possible genetic etiology for a patient with the phenotype of intrauterine growth restriction, microcephaly, developmental delay, failure to thrive, congenital bilateral hip dysplasia, cerebral and cerebellar atrophy, hydrocephalus, and congenital diaphragmatic hernia (CDH). Whole exome sequencing identified a novel de novo c.2722G > T (p.E908X) mutation in the Myosin Heavy Chain 10 gene (MYH10) which encodes for non-muscle heavy chain II B (NMHC IIB). Mutations in MYH10 have not been previously described in association with human disease. The E908X mutation is located in the coiled-coil region of the protein and is expected to delete the tail domain and disrupt filament assembly. Nonmuscle myosin IIs (NM IIs) are a group of ubiquitously expressed proteins, and NM II B is specifically enriched in neuronal tissue and is thought to be important in neuronal migration. It is also expressed in cardiac myocytes along with NM IIC. Homozygous NMHC II B-/B- mouse knockouts die by embryonic day (E)14.5 with severe cardiac defects (membranous ventricular septal defect and cardiac outflow tract abnormalities) and neurodevelopmental disorders (progressive hydrocephalus and neuronal migrational abnormalities). A heterozygous MYH10 loss of function mutation produces a severe neurologic phenotype and CDH but no apparent cardiac phenotype and suggests that MYH10 may represent a novel gene for brain malformations and/or CDH.