Shinichi Tsubata

Novel Gene Mutations in Patients With Left Ventricular Noncompaction or Barth Syndrome

Background — Mutations in the gene G4.5 result in a wide spectrum of severe infantile cardiomyopathic phenotypes, including isolated left ventricular noncompaction (LVNC), as well as Barth syndrome (BTHS) with dilated cardiomyopathy (DCM). The purpose of this study was to investigate patients with LVNC or BTHS for mutations in G4.5 or other novel genes. Methods and Results — DNA was isolated from 2 families and 3 individuals with isolated LVNC or LVNC with congenital heart disease (CHD), as well as 4 families with BTHS associated with LVNC or DCM, and screened for mutations by single-strand DNA conformation polymorphism analysis and DNA sequencing. In 1 family with LVNC and CHD, a C→T mutation was identified at nucleotide 362 of &agr;-dystrobrevin, changing a proline to leucine (P121L). Mutations in G4.5 were identified in 2 families with isolated LVNC: a missense mutation in exon 4 (C118R) in 1 and a splice donor mutation (IVS10+2T→A) in intron 10 in the other. In a family with cardiomyopathies ranging from BTHS or fatal infantile cardiomyopathy to asymptomatic DCM, a splice acceptor mutation in exon 2 of G4.5 (398-2 A→G) was identified, and a 1-bp deletion in exon 2 of G4.5, resulting in a stop codon after amino acid 41, was identified in a sporadic case of BTHS. Conclusions — These data demonstrate genetic heterogeneity in LVNC, with mutation of a novel gene, &agr;-dystrobrevin, identified in LVNC associated with CHD. In addition, these results confirm that mutations in G4.5 result in a wide phenotypic spectrum of cardiomyopathies.

Mutations in the human δ-sarcoglycan gene in familial and sporadic dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality. Two genes have been identified for the X-linked forms (dystrophin and tafazzin), whereas three other genes (actin, lamin A/C, and desmin) cause autosomal dominant DCM; seven other loci for autosomal dominant DCM have been mapped but the genes have not been identified. Hypothesizing that DCM is a disease of the cytoskeleton and sarcolemma, we have focused on candidate genes whose products are found in these structures. Here we report the screening of the human δ-sarcoglycan gene, a member of the dystrophin-associated protein complex, by single-stranded DNA conformation polymorphism analysis and by DNA sequencing in patients with DCM. Mutations affecting the secondary structure were identified in one family and two sporadic cases, whereas immunofluorescence analysis of myocardium from one of these patients demonstrated significant reduction in δ-sarcoglycan staining. No skeletal muscle disease occurred in any of these patients. These data suggest that δ-sarcoglycan is a disease-causing gene responsible for familial and idiopathic DCM and lend support to our “final common pathway” hypothesis that DCM is a cytoskeletalopathy.

Mutation analysis of the G4.5 gene in patients with isolated left ventricular noncompaction.

Mutations in the gene G4.5, originally associated with Barth syndrome, have been reported to result in a wide spectrum of severe infantile X-linked cardiomyopathies. The purpose of this study was to investigate patients with isolated left ventricular noncompaction (LVNC) for disease-causing mutations in G4.5. In 27 patients including 10 families with isolated LVNC, mutation analysis of G4.5 was performed using single-strand DNA conformation polymorphism (SSCP) analysis and DNA sequencing. A novel splice acceptor site mutation of intron 8 of G4.5 was identified in a family with severe infantile X-linked LVNC without the usual findings of Barth syndrome. This mutation results in deletion of exon 9 from the mRNA, and is predicted to significantly disrupt the protein product. Genotype-phenotype correlation of G4.5 mutations in all 38 cases reported in the literature to date revealed that there was no correlation between location or type of mutation and either cardiac phenotype or disease severity. We suggest that males presenting with cardiomyopathy, particularly during infancy, even in the absence of the typical signs of Barth syndrome, should be evaluated for mutations in G4.5.

Neutrophils and Mononuclear Cells Express Vascular Endothelial Growth Factor in Acute Kawasaki Disease: Its Possible Role in Progression of Coronary Artery Lesions

Kawasaki disease (KD) is a syndrome of systemic vasculitis of unknown etiology that is complicated by coronary artery lesions (CAL), leading occasionally to cardiac ischemic sequelae. To examine whether vascular endothelial growth factor (VEGF) is responsible for CAL in KD, we determined serum VEGF levels by ELISA and peripheral blood mononuclear cell (PBMC) and neutrophil VEGF expression by immunoblot analysis. Significantly increased levels of VEGF were demonstrated in acute KD as well as in other vasculitis syndromes (p < 0.0001). In the 10 KD patients with CAL, serum VEGF levels were maximal approximately 2 wk postonset when CAL generally develops and were significantly higher than in 20 patients without CAL (mean, 474 and 241 pg/mL, respectively;p = 0.00015). During the same period, immunoblot analysis revealed maximal VEGF expression in PBMC, corresponding to serum VEGF levels in most patients and being particularly marked in patients with CAL (p < 0.01). Neutrophils expressed VEGF only in the early stage of acute KD and declined rapidly in the majority of KD patients regardless of the presence of CAL, showing a strikingly different expression pattern than that for PBMC. Predominant VEGF expression by PBMC was also demonstrated in patients with other vasculitis syndromes and only faintly in normal controls. The results suggest that VEGF is generated dynamically in KD, presumably reflecting its disease activity. Neutrophil-derived VEGF may play a role in regulating early vascular responses, whereas PBMC-derived VEGF may contribute to later vascular injury and remodeling.

Additive Effect of Beraprost on Pulmonary Vasodilation by Inhaled Nitric Oxide in Children With Pulmonary Hypertension

Combined administration of inhaled nitric oxide and beraprost sodium resulted in a more intense decrease in pulmonary vascular resistance than nitric oxide given alone (mean -33% vs -45%, p <0.05), without serious systemic hypotension. Combined therapy with nitric oxide and beraprost sodium is highly desirable in treating primary and secondary pulmonary hypertension in children.

Successful thrombolytic therapy using tissue-type plasminogen activator in Kawasaki disease

Thrombolytic therapy using tissue-type plasminogen activator was performed in a 7-month-old boy with massive mural thrombi in large coronary aneurysms due to Kawasaki disease. Magnetic resonance imaging successfully demonstrated mural thrombi in both proximal and distal coronary aneurysms and their disappearance after thrombolytic therapy. We conclude that for preventing acute myocardial infarction and sudden death intravenous and intracoronary thrombolytic therapy with tissue-type plasminogen activator may help in infants and children with Kawasaki disease who have thrombi in coronary aneurysms.

Scheduled autologous blood donation at the time of cardiac catheterization in infants and children

Preoperative autologous blood donation is commonly performed to avoid homologous blood transfusion during cardiac operations in adult patients. 1 However, autologous blood donation for children is hampered by technical problems including lack of an adequate blood collection system and acute anemia after blood collection. Given the life span of children, it is most important to avoid the complications of homologous transfusion. 2 We describe a technique of scheduled autologous blood donation during preoperative cardiac catheterization and examine the efficacy and safety of this method for use in infants and children. Technique. Cardiac catheterization was performed about 2 weeks before elective operations in infants and children weighing at least 5 kg. Autologous blood donation was performed in patients with a hematocrit value of 33% or more and a hemoglobin value of 11 gm/dl or more. Sedation was achieved with thiopental sodium and local anesthesia was achieved with lidocaine hydrochloride. Sheaths were inserted into the femoral artery and vein. After hemodynamic measurements, but before contrast angiography, 10 ml/kg of blood was collected via the arterial sheath. The same volume of lactated Ringers solution was infused at the same rate through the venous sheath. Collected blood was stored as packed red cells and plasma or as whole blood. Blood erythropoietin concentrations were measured before and after blood collection, and recombinant human erythropoietin (100 U/kg) was administered intravenously to acyanotic patients on the first and seventh days after blood collection. Cyanotic patients were not treated with recombinant human erythropoietin. Each patient was given ferrous sulfate (2 mg/ kg) orally every day. Results. From October 1995 through September 1997, preoperative autologous blood donation was performed in 27 children, including 13 infants (16 boys and 11 girls). Their ages ranged from 6 months to 6 years, 8 months (average 1.9 -+ 2.1 years). Their body weights ranged from 5.8 kg to 20.2 kg (average 9.7 -+ 5.5 kg). The patients

Gonadal mosaicism of a TAZ (G4.5) mutation in a Japanese family with Barth syndrome and left ventricular noncompaction

TAZ (G4.5) was initially identified as the gene associated with Barth syndrome and left ventricular noncompaction (LVNC). The purpose of this study was to investigate patients with LVNC for disease-causing mutations in TAZ. In 124 Japanese patients, including 50 families, mutation analysis of TAZ was performed using DNA sequencing. A splice donor mutation was identified in two brothers with Barth syndrome and LVNC, and a sister who was asymptomatic. However, the variant was not identified in either parent or the maternal grandparents, all of whom were asymptomatic. Due to the recurrent inheritance of this variant by each of the children we concluded that this was evidence of gonadal mosaicism in the obligate carrier mother, the first reported occurrence of this in Barth syndrome.

A novel method for indexing echocardiographic left ventricular mass in infants, children and adolescents: Evaluation of obesity-induced left ventricular hypertrophy

Abstract Background: Measurement of left ventricular mass (LVM) is important to the diagnosis of left ventricular hypertrophy in children with various cardiovascular diseases. The purpose of this study was to determine the most appropriate method for standardization of LVM and to evaluate obesity‐induced left ventricular hypertrophy in children across the entire age range, from infancy through adolescence.

Bronchial hyper-responsiveness to inhaled histamine in children with congenital heart disease

In order to assess bronchial responsiveness in patients with congestive heart failure secondary to congenital heart disease, we performed a histamine inhalation test while monitoring transcutaneous oxygen tension and compared the respiratory threshold to histamine with that obtained in patients with bronchial asthma. The inhalation test was performed by doubling concentrations of histamine solution for 2 min at 1 min intervals. The respiratory threshold of histamine was defined as the minimal concentration causing a drop in transcutaneous oxygen tension greater than 10% from baseline. Six of 10 patients with congenital heart disease and all of 12 patients with bronchial asthma had bronchial hyper‐responsiveness to histamine. The mean of histamine concentration was 2750μg/mL and 937μg/mL, respectively. During the histamine inhalation test, respiratory resistance gradually increased in congenital heart disease patients. This was measured by the linear slope of transcutaneous oxygen pressure (‐1.08 ± 0.75 mmHg/min), whereas in the bronchial asthma patients it rapidly decreased at the inflection point (‐4.19 ± 1.86 mmHg/min). We conclude that children with congestive heart failure had bronchial hyper‐responsiveness. We suggest bronchial hyper‐responsiveness to inhaled histamine in congestive heart failure was caused by the gradual increased respiratory resistance, which was different from that of bronchial asthma.