Gernot Grangl

CCC- and WASH-mediated endosomal sorting of LDLR is required for normal clearance of circulating LDL

The low-density lipoprotein receptor (LDLR) plays a pivotal role in clearing atherogenic circulating low-density lipoprotein (LDL) cholesterol. Here we show that the COMMD/CCDC22/CCDC93 (CCC) and the Wiskott–Aldrich syndrome protein and SCAR homologue (WASH) complexes are both crucial for endosomal sorting of LDLR and for its function. We find that patients with X-linked intellectual disability caused by mutations in CCDC22 are hypercholesterolaemic, and that COMMD1-deficient dogs and liver-specific Commd1 knockout mice have elevated plasma LDL cholesterol levels. Furthermore, Commd1 depletion results in mislocalization of LDLR, accompanied by decreased LDL uptake. Increased total plasma cholesterol levels are also seen in hepatic COMMD9-deficient mice. Inactivation of the CCC-associated WASH complex causes LDLR mislocalization, increased lysosomal degradation of LDLR and impaired LDL uptake. Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is associated with hypercholesterolaemia in humans. Altogether, this study provides valuable insights into the mechanisms regulating cholesterol homeostasis and LDLR trafficking.

Reference Values and Calculation of z-Scores of Echocardiographic Measurements of the Normal Pediatric Right Ventricle

Determination of right ventricular (RV) size and function has gained more interest in recent years in adults and children, especially in patients with congenital heart disease. Data on normal RV size parameters in children are scant. The aim of this study was to investigate growth-related changes in RV internal dimensions in a healthy pediatric cohort and the predictive value of RV parameters in identifying enlarged right ventricles in children with secundum-type atrial septal defects (ASD). A prospective study was conducted in a group of 576 healthy children (aged 1 day to 18 years) and 37 children (aged 1.4 to 17.7 years) with moderate-sized to large ASDs. The effects of age, body length, body weight, and body surface area were determined on the following RV parameters: end-diastolic basal diameter, end-diastolic midcavity diameter, end-diastolic length, end-systolic length, end-diastolic area, and end-systolic area. The predictive value of normal values stratified for age, body weight, body length, and body surface area was tested in children with ASDs. RV end-diastolic basal diameter, end-diastolic midcavity diameter, end-diastolic length, end-systolic length, end-diastolic area, and end-systolic area showed positive correlations with age, body length, body surface area, and body weight. In this population, RV z scores showed high specificity for detecting patients with ASDs, with sensitivity up to 89%, especially in children <8 years of age. In conclusion, the normal ranges of pediatric RV internal dimensions are provided. The z scores of these RV parameters were also calculated. Normal RV z scores might be important predictors in identifying enlarged right ventricles in patients with ASDs.

Missense variant in CCDC22 causes X-linked recessive intellectual disability with features of Ritscher-Schinzel/3C syndrome

Ritscher-Schinzel syndrome (RSS)/3C (cranio-cerebro-cardiac) syndrome (OMIM#220210) is a rare and clinically heterogeneous developmental disorder characterized by intellectual disability, cerebellar brain malformations, congenital heart defects, and craniofacial abnormalities. A recent study of a Canadian cohort identified homozygous sequence variants in the KIAA0196 gene, which encodes the WASH complex subunit strumpellin, as a cause for a form of RSS/3C syndrome. We have searched for genetic causes of a phenotype similar to RSS/3C syndrome in an Austrian family with two affected sons. To search for disease-causing variants, whole-exome sequencing (WES) was performed on samples from two affected male children and their parents. Before WES, CGH array comparative genomic hybridization was applied. Validation of WES and segregation studies was done using routine Sanger sequencing. Exome sequencing detected a missense variant (c.1670A>G; p.(Tyr557Cys)) in exon 15 of the CCDC22 gene, which maps to chromosome Xp11.23. Western blots of immortalized lymphoblastoid cell lines (LCLs) from the affected individual showed decreased expression of CCDC22 and an increased expression of WASH1 but a normal expression of strumpellin and FAM21 in the patients cells. We identified a variant in CCDC22 gene as the cause of an X-linked phenotype similar to RSS/3C syndrome in the family described here. A hypomorphic variant in CCDC22 was previously reported in association with a familial case of syndromic X-linked intellectual disability, which shows phenotypic overlap with RSS/3C syndrome. Thus, different inactivating variants affecting CCDC22 are associated with a phenotype similar to RSS/3C syndrome.

Normal Reference Values and z Scores of the Pulmonary Artery Acceleration Time in Children and Its Importance for the Assessment of Pulmonary HypertensionCLINICAL PERSPECTIVE

Background— Pulsed-wave Doppler determination of the pulmonary artery acceleration time (PAAT) as a surrogate for pulmonary artery pressure was found to be of clinical value for assessment of pulmonary hypertension (PH) with studies to date exclusively performed in adults. This study aims to provide representative, normal reference values for PAAT in children of all ages. Moreover, we validated abnormal PAAT values in 54 children with PH. Methods and Results— We conducted a prospective echocardiographic study in 756 healthy children (aged 1 day to 18 years) and in 54 children with PH. Possible associations of age, body length, body weight, body surface area, and heart rate on PAAT were investigated. The PAAT correlated positively with age (r=0.848), body length (r=0.871), body surface area (r=0.856), and body weight (r=0.825) and negatively with heart rate (r=−0.906). PAAT increased with age (neonates: median: 81 ms, range: 53–104; 18th year of life: median: 151 ms, range: 107–187). Receiver operating characteristic analysis for detecting PH patients using age-specific z scores showed an excellent performance of PAAT (P<0.001; area under the curve, 0.98; 95% confidence interval, 0.97–0.99) with a best cutoff score according to Youden index of –1.565 (sensitivity: 92%, specificity: 96%). PAAT values of PH patients negatively correlated (&rgr;=−0.497) with pulmonary vascular resistance. Conclusions— The PAAT normal reference values and z scores we provide here will be useful to identify children with a shortened PAAT. Abnormal PAAT values with scores <−2 were predictive of PH.

Right ventricular base/apex ratio in the assessment of pediatric pulmonary arterial hypertension: Results from the European Pediatric Pulmonary Vascular Disease Network

Echocardiographic determination of RV end‐systolic base/apex (RVES b/a) ratio was proposed to be of clinical value for assessment of pulmonary arterial hypertension (PAH) in adults.

Racial differences of the tricuspid annular plane systolic excursion.

Given that this parameter is determined by the pulmonary blood flow velocity and the diameter of the pulmonary orifice in the RV outflow tract (RVOT), we may state that the RVOT proximal diameter has been shown to be an age-dependent parameter. 2 Using available age-related values in their statistical analysis would perhaps result in a higher significant correlation between TAPSE and RVSV/BSA then was observed in their study. 1

Serum Bile Acids in Repaired Tetralogy of Fallot: A Marker for Liver and Heart?

Background and Aims Patients with repaired tetralogy of Fallot may develop chronic right ventricular dysfunction and hepatic congestion over time. We hypothesized that bile acid metabolism is altered in repaired tetralogy of Fallot patients and therefore sought to correlate right ventricular indices with serum bile acid levels. Methods Indexed right ventricular end diastolic volume, as assessed by cardiac magnetic-resonance imaging, was classified as <100ml/m2 (Group 1, n = 5), 100–150ml/m2 (Group 2, n = 18), and >150ml/m2 (Group 3, n = 6) in 29 patients with repaired tetralogy of Fallot. Pulmonary regurgitation fraction and right ventricular ejection fraction were calculated. The serum bile acid profile, including 15 species, in these patients was determined by liquid chromatography coupled with mass spectrometry. Results Serum bile acid levels increased from Group 1 to Group 3 (2.5 ± 0.7; 4.1 ± 2.5; 6.0 ± 2.8 μmol/l, respectively) with significantly increased bile acid values in Group 3 compared to Group 1 (p≤0.05). In Group 3, but not in Group 1 and 2, a significant increase in glycine-conjugated bile acids was observed. Pulmonary regurgitation fraction increased (12 ± 1; 28 ± 16; 43 ± 3%, Groups 1–3, respectively) and right ventricular ejection fraction decreased (48.4 ± 6.4; 48.5 ± 6.5; 42.1 ± 5.3%, Groups 1–3, respectively) with rising indexed right ventricular end diastolic volume. Conclusions These preliminary results suggest that serum bile acid levels are positively correlated with indexed right ventricular end-diastolic volume in patients with repaired tetralogy of Fallot; however, this needs to be confirmed in a larger patient cohort.

Tricuspid Annular Plane Systolic Excursion Is Reduced in Infants with Pulmonary Hypertension Value of Tricuspid Annular Plane Systolic Excursion (TAPSE) to Determine Right Ventricular Function in Various Conditions of Pediatric Pulmonary Hypertension

have studied right ventricular (RV) systolicfunction in infants with pulmonary hypertension(PH) due to bronchopulmonary dysplasia, con-genital diaphragmatic hernia, or idiopathic PH.For assessment of RV systolic function, the tricus-pid annular peak systolic excursion (TAPSE), thetricuspid annular peak systolic velocity (S

Relevance of Right Ventricular Outflow Tract Velocity Time Integral (RVOT VTI) and Tricuspid Regurgitation Velocity/RVOT VTI Ratio Determination in Children Following Heart Transplantation

We read with interest the article “Right Ventricular Dysfunction as an Echocardiographic Measure of Acute Rejection Following Heart Transplantation in Children” by Aggarwal et al. [1]. Authors investigated the role of RV functional parameters as well as pulmonary vascular compliance measures by echocardiography in the detection of acute allograft rejection (AAR) following orthotopic heart transplantation (OHT) in children [1]. The tricuspid regurgitation velocity (TRv)/right ventricular outflow tract velocity time integral (RVOT VTI) ratio, as a reliable measure of pulmonary blood flow in adults with PH [2–4], approximates the ratio of pulmonary artery pressure to pulmonary blood flow. Abbas et al. [2] nicely have shown that the ratio of TRv/RVOT VTI is related to pulmonary vascular resistance (PVR). As the PVR increases, earlier and enhanced reflections of the pressure wave profile of RVOT appear along with substantial changes in RVOT VTI [5]. Aggarwal et al. [1] found that the PVR, as assessed by the TRv/RVOT VTI ratio, was significantly higher at the time of AAR [1]. There was no difference in the TRv but significantly lower VTI values were detected, suggesting a decreased RV output. This is in agreement to recent data [6] showing impaired RVOT VTI in children with increased RV afterload due to pulmonary hypertension (PH). In this patient group, the TRV/RVOT VTI ratio was found to rise with increasing RV pressure [6]. Aggarwal et al. [1] describe that the age range of the children at the time of OHT was 2 months to 12.7 years. In our opinion it would be important to use age-related RVOT VTI values in children as reference, due to the variability of RVOT VTI values due to age and growth. We want to add that data of RVOT VTI normative values and z-scores are currently available [6, 7]. It would be of interest for the audience of Pediatric Cardiology in which way the observed differences of VTI values during AAR would have been more relevant if they were compared to available age-dependent parameters [7]. Using these agerelated normative values the authors would have been able to compare the measured RVOT VTI values of their patients with respective age-related RVOT VTI values, which in our opinion would have improved the statistical power of their analysis. With the currently available data and the fact that the TRv/RVOT VTI ratio [1, 2, 6] provides a non-invasive and simple method for identifying RV flow disturbances, we want to encourage the use of this ratio in clinical practice, implicating that an increased ratio should lead to a more invasive determination. We want to thank the authors for addressing the need for careful and systematic evaluation of RV function and output in children with AAR after OHT and want to highlight their study, which now for the first time provides non-invasive values of RV dysfunction during AAR following OHT in children [1]. These non-invasive echocardiographic parameters of RV function can assist in the evaluation of OHT patients in routine follow-up and may reduce costs by decreasing the number of more advanced investigations such as myocardial biopsies or cardiac magnet resonance imaging [8]. Even more, as a non-invasive parameter to detect impaired pulmonary blood flow in children with PH, we suggest including RVOT VTI and the TRV/ RVOT VTI ratio in echocardiographic protocols when evaluating children with a suspected PH. * Martin Koestenberger Martin.Koestenberger@medunigraz.at; koestenbergerm@gmx.at

The right ventricular outflow tract in pediatric pulmonary hypertension-Data from the European Pediatric Pulmonary Vascular Disease Network

The right ventricular outflow tract (RVOT) is pivotal for adequate RV function and known to be adversely affected by elevated pulmonary arterial pressure (PAP) in adults with pulmonary hypertension (PH). Aim of this study was to determine the effects of increased RV pressure afterload in children with PH on RVOT size, function, and flow parameters.