Genetic etiology of truncus arteriosus excluding 22q11.2 deletion syndrome and identification of c.1617del, a prevalent variant in TMEM260, in the Japanese population.

Truncus Arteriosus (TA) is a congenital heart disease characterized by a single common blood vessel emerging from the right and left ventricles instead of the main pulmonary artery and aorta. TA accounts for 4% of all critical congenital heart diseases. The most common cause of TA is 22q11.2 deletion syndrome, accounting for 12-35% of all TA cases. However, no major causes of TA other than 22q11.2 deletion have been reported. We performed whole-genome sequencing of 11 Japanese patients having TA without 22q11.2 deletion. Among five patients, we identified pathogenic variants in TMEM260; the biallelic loss-of-function variants of which have recently been associated with structural heart defects and renal anomalies syndrome (SHDRA). In one patient, we identified a de novo pathogenic variant in GATA6, and in another patient, we identified a de novo probably pathogenic variant in NOTCH1. Notably, we identified a prevalent variant in TMEM260 (ENST00000261556.6), c.1617del (p.Trp539Cysfs*9), in 8/22 alleles among the 11 patients. The c.1617del variant was estimated to occur approximately 23 kiloyears ago. Based on the allele frequency of the c.1617del variant in the Japanese population (0.36%), approximately 26% of Japanese patients afflicted with TA could harbor homozygous c.1617del variants. This study highlights TMEM260, especially c.1617del, as a major genetic cause of TA in the Japanese population.

Correction: Biallelic GALM pathogenic variants cause a novel type of galactosemia.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Recurrent de novo MAPK8IP3 variants cause neurological phenotypes.

c-Jun-amino-terminal kinase-interacting protein 3 (JIP3), encoded by MAPK8IP3, is an adaptor protein of the kinesin-1 complex and essential for axonal transport in neurons. However, an association between MAPK8IP3 variants and human disease has not been established. We identified 5 individuals from four families with recurrent de novo variants c.1732C>T (p.Arg578Cys) and c.3436C>T (p.Arg1146Cys) in MAPK8IP3. The core phenotype includes spastic diplegia, intellectual disability, cerebral atrophy, and corpus callosum hypoplasia. Zebrafish embryos overexpressing human mutant JIP3 showed axon varicosities of the posterior lateral line nerve, suggesting an adverse effect on the developing axons. Our results suggest that MAPK8IP3 variants cause a neurodevelopmental disease. ANN NEUROL 2019;85:927-933.

Biallelic GALM pathogenic variants cause a novel type of galactosemia.

PURPOSE: Galactosemia is caused by metabolic disturbances at various stages of galactose metabolism, including deficiencies in enzymes involved in the Leloir pathway (GALT, GALK1, and GALE). Nevertheless, the etiology of galactosemia has not been identified in a subset of patients. This study aimed to explore the causes of unexplained galactosemia. METHODS: Trio-based exome sequencing and/or Sanger sequencing was performed in eight patients with unexplained congenital galactosemia. In vitro enzymatic assays and immunoblot assays were performed to confirm the pathogenicity of the variants. RESULTS: The highest blood galactose levels observed in each patient were 17.3-41.9 mg/dl. Bilateral cataracts were observed in two patients. In all eight patients, we identified biallelic variants (p.Arg82*, p.Ile99Leufs*46, p.Gly142Arg, p.Arg267Gly, and p.Trp311*) in the GALM encoding galactose mutarotase, which catalyzes epimerization between ß- and α-D-galactose in the first step of the Leloir pathway. GALM enzyme activities were undetectable in lymphoblastoid cell lines established from two patients. Immunoblot analysis showed the absence of the GALM protein in the patients' peripheral blood mononuclear cells. In vitro GALM expression and protein stability assays revealed altered stabilities of the variant GALM proteins. CONCLUSION: Biallelic GALM pathogenic variants cause galactosemia, suggesting the existence of type IV galactosemia.

The prevalence of GALM mutations that cause galactosemia: A database of functionally evaluated variants.

Galactosemia is a metabolic disorder that affects the appropriate metabolism of ß-D-galactose. Deficiencies in three of the enzymes of the Leloir pathway, namely, GALT, GALK1, or GALE, are characterized as type I, II, and III galactosemia, respectively. Recently, we reported a novel type of galactosemia (type IV galactosemia) due to biallelic GALM mutations. Genetic diagnosis is indispensable for diagnosing GALM deficiency because no biochemical diagnosis method has been established. Given that apparently pathogenic variants in GALM are found in public variant databases, we presumed the presence of pathogenic variants that have not been reported. In this study, we explore 67 GALM variants that are prevalent in the ExAC database, including 57 missense variants, 7 stop-gain variants, 2 frameshift variants, and 1 splice-site variant. We performed an in vitro expression assay and an enzyme activity assay. Among the 66 variants except for 1 splice-site variant, 29 produced no or faint protein expression and were judged as pathogenic variants. Furthermore, the remaining 37 variants were evaluated by enzyme activity assay. Two showed mildly reduced enzyme activity and were classified as benign. Based on our study, the estimated incidence of GALM deficiency is 1:228,411 in all populations, 1:10,388 in the African population, and 1:80,747 in the Japanese population. Our GALM mutation database is useful for the genetic diagnosis of GALM deficiency.

Efficacy and Safety of Low-Dose Amiodarone Therapy for Tachyarrhythmia in Congenital Heart Disease.

Amiodarone (AMD) is a class III anti-arrhythmic drug that is highly effective for tachyarrhythmia treatment. AMD is widely used in adults with congenital heart disease (CHD); however, higher doses of AMD (> 200 mg/day) can cause various non-cardiac side effects. The purpose of this study was to assess the efficacy, safety, and adverse events of low-dose AMD (≤ 200 mg/day) for tachyarrhythmia in patients with CHD. We retrospectively studied 80 patients with CHD and tachyarrhythmia who received oral low-dose AMD (≤ 200 mg/day) from January 2004 to March 2016. Low-dose AMD therapy was used to treat supraventricular tachycardia (SVT) in 51 patients and ventricular tachycardia (VT) in 29 patients. After a mean follow-up of 2.9 years for SVT and 3.2 years for VT, 36% and 65% of the patients with SVT and VT, respectively, were free from a first tachyarrhythmia recurrence for 3 years. The incidence of AMD-induced side effects was 23%, and all these cases consisted of thyroid dysfunction. Low-dose AMD was effective for the treatment of tachyarrhythmia in patients with CHD and had a relatively low incidence of side effects. These findings suggest that low-dose AMD is useful and effective for decreasing the frequency of tachyarrhythmia in patients with CHD and has a low incidence of side effects.

Male infant with Noonan syndrome with RAF-1 gene mutation who survived hypertrophic cardiomyopathy-induced fatal heart failure and uncontrollable arrhythmias.

Noonan syndrome (NS) is a congenital disease with characteristic facial features as well as heart disease, short stature and thoracic abnormalities. More than eighty per cent of patients with NS show several cardiac disorders including pulmonary valvular stenosis, hypertrophic cardiomyopathy (HCM) and/or atrial septal defects. HCM is a serious cardiac comorbidity in patients with NS, especially in those who are diagnosed within 6 months of age with congestive heart failure. Arrhythmia with or without HCM in NS is a rare comorbidity with a complicated clinical course and poor prognosis.In this manuscript, we present the case of a male infant with NS with RAF1 gene mutation, who showed various types of arrhythmias. He developed life-threatening heart failure and uncontrollable arrhythmias. We attempted several antiarrhythmic agents and finally controlled the arrhythmias to establish a normal sinus rhythm with a combination of amiodarone and flecainide.

Two Distinct Cases of Adult-onset Kawasaki Disease.

Kawasaki disease (KD) is a systemic vasculitis syndrome that mostly affects children under 4 years old. Among the reported KD cases, only 1% were over 10 years old. We herein report 2 cases of adult-onset KD (AKD) in 19- and 17-year-old boys diagnosed with a persistent fever and cervical lymphadenitis. Both patients showed cardiac complications, such as coronary artery dilation and myocarditis. Repeated intravenous immunoglobulin therapy was effective in the 19-year-old, while plasma exchange therapy was needed for the 17-year-old, with no sequelae noted at discharge. KD should be considered as a differential diagnosis for persistent fever in adults.

Thoracic Empyema Secondary to Congenital Chylothorax in a 14-Month-Old Boy with Noonan Syndrome.

Thoracic empyema usually occurs as a complication of bacterial pneumonia, but in rare cases, it is caused by hematogenous dissemination secondary to nonpulmonary diseases. Congenital chylothorax or chylothorax in children is associated with maldevelopment of the lymphatic system, nonimmune hydrops fetalis, several syndromes including Down syndrome, Noonan syndrome, or Turner syndrome, a complication of thoracic surgery, right heart failure with high central venous pressure, or tumors. There are very few reports of empyema associated with preexisting chylothorax. In the present study, we describe a rare case of thoracic empyema associated with congenital chylothorax and supravalvular pulmonary stenosis associated with clinically diagnosed Noonan syndrome. It is necessary to closely monitor patients with chylothorax because they are at risk of developing severe lung infections, such as pleural empyema or lung abscesses.

Bilateral lung transplantation in a 9-year-old girl with bronchopulmonary dysplasia with pulmonary hypertension.

BACKGROUND: Bronchopulmonary dysplasia (BPD) is a chronic respiratory disease that occurs in premature infants and the prognosis is variable depending on the comorbidities including fibrosis, emphysema, or pulmonary hypertension (PH). We present a case of a 9-year-old girl who developed PH associated with severe BPD (BPD-PH) and underwent bilateral lung transplantation (BLTx). Case description A 9-year-old girl was admitted to our department to undergo BLTx. She was born at 23 weeks and 4 days gestation with a weight of 507 g. She received ventilation for the first 2 months and required further respiratory care due to repetitive, severe respiratory infections. She was diagnosed with BPD-PH at 6 months of age and oral administration of pulmonary vasodilators were initiated. She was registered as a lung transplant candidate at 4 years of age after the life-threatening exacerbation. Chest computed tomography (CT) revealed severe lung conditions with ground-glass opacities and emphysematous low-density areas in the upper and lower lobes. BLTx from a brain-dead male donor was performed. The pathological findings of her resected lung revealed saccular, hypoplastic lung with alveolar repair/regeneration, and medial hypertrophy and muscularization of peripheral arteries. The postoperative course was mostly uneventful. She was free from oxygen administration and showed no signs of PH after 6 months of the surgery. CONCLUSION: This is the first case report of BLTx in a pediatric, irreversible BPD-PH patient with detailed pathohistological findings and clinical examination. Lung transplantation is one of the treatment options for severe BPD-PH.

A sublethal ATP11A mutation associated with neurological deterioration causes aberrant phosphatidylcholine flipping in plasma membranes.

ATP11A translocates phosphatidylserine (PtdSer), but not phosphatidylcholine (PtdCho), from the outer to the inner leaflet of plasma membranes, thereby maintaining the asymmetric distribution of PtdSer. Here, we detected a de novo heterozygous point mutation of ATP11A in a patient with developmental delays and neurological deterioration. Mice carrying the corresponding mutation died perinatally of neurological disorders. This mutation caused an amino acid substitution (Q84E) in the first transmembrane segment of ATP11A, and mutant ATP11A flipped PtdCho. Molecular dynamics simulations revealed that the mutation allowed PtdCho binding at the substrate entry site. Aberrant PtdCho flipping markedly decreased the concentration of PtdCho in the outer leaflet of plasma membranes, whereas sphingomyelin (SM) concentrations in the outer leaflet increased. This change in the distribution of phospholipids altered cell characteristics, including cell growth, cholesterol homeostasis, and sensitivity to sphingomyelinase. Matrix-assisted laser desorption ionization-imaging mass spectrometry (MALDI-IMS) showed a marked increase of SM levels in the brains of Q84E-knockin mouse embryos. These results provide insights into the physiological importance of the substrate specificity of plasma membrane flippases for the proper distribution of PtdCho and SM.

Modulation of luminescence intensity of lanthanide complexes by photoinduced electron transfer and its application to a long-lived protease probe.

Luminescent lanthanide complexes (Tb(3+), Eu(3+), etc.) have excellent properties for biological applications, including extraordinarily long lifetimes and large Stokes shifts. However, there have been few reports of lanthanide-based functional probes, because of the difficulty in designing suitable complexes with a luminescent on/off switch. Here, we have synthesized a series of complexes which consist of three moieties: a lanthanide chelate, an antenna, and a luminescence off/on switch. The antenna is an aromatic ring which absorbs light and transmits its energy to the metal, and the switch is a benzene derivative with a different HOMO level. If the HOMO level is higher than a certain threshold, the complex emits no luminescence at all, which indicates that the lanthanide luminescence can be modulated by photoinduced electron transfer (PeT) from the switch to the sensitizer. This approach to control lanthanide luminescence makes possible the rational design of functional lanthanide complexes, in which the luminescence property is altered by a biological reaction. To exemplify the utility of our approach to the design of lanthanide complexes with a switch, we have developed a novel protease probe, which undergoes a significant change in luminescence intensity upon enzymatic cleavage of the substrate peptide. This probe, combined with time-resolved measurements, was confirmed in model experiments to be useful for the screening of inhibitors, as well as for clinical diagnosis.