Hideki Motomura

Novel Calmodulin Mutations Associated With Congenital Arrhythmia Susceptibility

Background—Genetic predisposition to life-threatening cardiac arrhythmias such as congenital long-QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT) represent treatable causes of sudden cardiac death in young adults and children. Recently, mutations in calmodulin (CALM1, CALM2) have been associated with severe forms of LQTS and CPVT, with life-threatening arrhythmias occurring very early in life. Additional mutation-positive cases are needed to discern genotype–phenotype correlations associated with calmodulin mutations. Methods and Results—We used conventional and next-generation sequencing approaches, including exome analysis, in genotype-negative LQTS probands. We identified 5 novel de novo missense mutations in CALM2 in 3 subjects with LQTS (p.N98S, p.N98I, p.D134H) and 2 subjects with clinical features of both LQTS and CPVT (p.D132E, p.Q136P). Age of onset of major symptoms (syncope or cardiac arrest) ranged from 1 to 9 years. Three of 5 probands had cardiac arrest and 1 of these subjects did not survive. The clinical severity among subjects in this series was generally less than that originally reported for CALM1 and CALM2 associated with recurrent cardiac arrest during infancy. Four of 5 probands responded to &bgr;-blocker therapy, whereas 1 subject with mutation p.Q136P died suddenly during exertion despite this treatment. Mutations affect conserved residues located within Ca2+-binding loops III (p.N98S, p.N98I) or IV (p.D132E, p.D134H, p.Q136P) and caused reduced Ca2+-binding affinity. Conclusions—CALM2 mutations can be associated with LQTS and with overlapping features of LQTS and CPVT.

Sodium Channelopathy Underlying Familial Sick Sinus Syndrome With Early Onset and Predominantly Male Characteristics

Background—Sick sinus syndrome (SSS) is a common arrhythmia often associated with aging or organic heart diseases but may also occur in a familial form with a variable mode of inheritance. Despite the identification of causative genes, including cardiac Na channel (SCN5A), the pathogenesis and molecular epidemiology of familial SSS remain undetermined primarily because of its rarity. Methods and Results—We genetically screened 48 members of 15 SSS families for mutations in several candidate genes and determined the functional properties of mutant Na channels using whole-cell patch clamping. We identified 6 SCN5A mutations including a compound heterozygous mutation. Heterologously expressed mutant Na channels showed loss-of-function properties of reduced or no Na current density in conjunction with gating modulations. Among 19 family members with SCN5A mutations, QT prolongation and Brugada syndrome were associated in 4 and 2 individuals, respectively. Age of onset in probands carrying SCN5A mutations was significantly less (mean±SE, 12.4±4.6 years; n=5) than in SCN5A-negative probands (47.0±4.6 years; n=10; P<0.001) or nonfamilial SSS (74.3±0.4 years; n=538; P<0.001). Meta-analysis of SSS probands carrying SCN5A mutations (n=29) indicated profound male predominance (79.3%) resembling Brugada syndrome but with a considerably earlier age of onset (20.9±3.4 years). Conclusions—The notable pathophysiological overlap between familial SSS and Na channelopathy indicates that familial SSS with SCN5A mutations may represent a subset of cardiac Na channelopathy with strong male predominance and early clinical manifestations.

Seroprevalence of rubella in the cord blood of pregnant women and congenital rubella incidence in Nha Trang, Vietnam

To investigate susceptibility to and factors associated with rubella infection among pregnant mothers and to estimate the burden of congenital rubella infection (CRI) in Vietnam where rubella-containing vaccine (RCV) is not included in the routine immunization program, we conducted a prospective cohort study in Nha Trang, Vietnam between 2009 and 2010. Rubella-specific immunoglobulin-M and immunoglobulin-G were investigated in cord blood samples by enzyme immunoassay. Corresponding clinical-epidemiological data were analyzed and the national congenital rubella syndrome (CRS) incidence was estimated using modeling. We enrolled 1988 pairs of mothers aged 17-45 years and their newborn babies. No mothers had received RCV. Multivariate analysis revealed that mothers aged 17-24 (aOR 2.5, 95% CI: 1.7-3.8) or 25-34 (1.4, 1.0-2.1) years were more likely to be susceptible than those aged 35-45 years. Overall 28.9% (574/1988, 95% CI: 26.9-30.9%) of mothers were seronegative. The CRI rate was 151 (95% CI: 0-322) per 100,000 live births. Modeling estimated that 3788 babies (95% CI: 3283-4143) were born with CRS annually in Vietnam with an overall CRS incidence of 234 (95% CI: 207-262) cases per 100,000 live births. A substantial proportion of women of childbearing age (WCBA) are at risk of rubella infection during pregnancy and this can result in a high frequency of miscarriage or burden of CRS across Vietnam. Prompt introduction of RCV into national immunization program with catch-up vaccination to children and WCBA will reduce CRI in Vietnam.

Allele-specific ablation rescues electrophysiological abnormalities in a human iPS cell model of long-QT syndrome with a CALM2 mutation

&NA; Calmodulin is a ubiquitous Ca2+ sensor molecule encoded by three distinct calmodulin genes, CALM1‐3. Recently, mutations in CALM1‐3 have been reported to be associated with severe early‐onset long‐QT syndrome (LQTS). However, the underlying mechanism through which heterozygous calmodulin mutations lead to severe LQTS remains unknown, particularly in human cardiomyocytes. We aimed to establish an LQTS disease model associated with a CALM2 mutation (LQT15) using human induced pluripotent stem cells (hiPSCs) and to assess mutant allele‐specific ablation by genome editing for the treatment of LQT15. We generated LQT15‐hiPSCs from a 12‐year‐old boy with LQTS carrying a CALM2‐N98S mutation and differentiated these hiPSCs into cardiomyocytes (LQT15‐hiPSC‐CMs). Action potentials (APs) and L‐type Ca2+ channel (LTCC) currents in hiPSC‐CMs were analyzed by the patch‐clamp technique and compared with those of healthy controls. Furthermore, we performed mutant allele‐specific knockout using a CRISPR‐Cas9 system and analyzed electrophysiological properties. Electrophysiological analyses revealed that LQT15‐hiPSC‐CMs exhibited significantly lower beating rates, prolonged AP durations, and impaired inactivation of LTCC currents compared with control cells, consistent with clinical phenotypes. Notably, ablation of the mutant allele rescued the electrophysiological abnormalities of LQT15‐hiPSC‐CMs, indicating that the mutant allele caused dominant‐negative suppression of LTCC inactivation, resulting in prolonged AP duration. We successfully recapitulated the disease phenotypes of LQT15 and revealed that inactivation of LTCC currents was impaired in CALM2‐N98S hiPSC model. Additionally, allele‐specific ablation using the latest genome‐editing technology provided important insights into a promising therapeutic approach for inherited cardiac diseases.

Mortality Associated With Pulmonary Hypertension in Congenital Rubella Syndrome

OBJECTIVE: Outbreaks of rubella and congenital rubella syndrome (CRS) continue to arise in various countries where a rubella-containing vaccine is not included in the national immunization program. After a large-scale rubella outbreak in 2011, CRS cases emerged in Vietnam. The aim of this study was to clarify the clinical features of these cases with an emphasis on cardiovascular complications and outcomes. METHODS: From October 2011 to September 2012, we conducted a prospective surveillance study of infants <12 months of age who had manifestations suggesting CRS at the only referral hospital in Khanh Hoa Province. These infants underwent standard examinations, echocardiography, cranial ultrasonography, automated auditory brainstem responses, blood cell count measurements, and rubella-specific antibody testing. Detected cardiovascular defects were regularly followed with echocardiography. RESULTS: We enrolled 38 cases of CRS characterized by a low birth weight (71%), cardiovascular defects (72%), cataracts (13%), hearing impairment (93%), purpura (84%), hepatosplenomegaly (68%), and thrombocytopenia (76%). Patent ductus arteriosus, the most common cardiovascular complication, was often associated with progressive pulmonary hypertension (PH). As of January 2013, 13 infants (34%) had died, and PH was significantly more frequent among the fatalities (P = .004); however, therapeutic closure of the ductus reversed the PH in several cases. CONCLUSIONS: PH-associated mortality is high among infants who have CRS in Vietnam. Providing proper assessments, continuous follow-up, and timely intervention for cardiovascular defects is critical for the management of CRS patients. Echocardiography is of diagnostic and prognostic value and can support better clinical management of CRS, even in a developing country setting.

Kawasaki disease-associated MERS: pathological insights from SPECT findings.

We report for the first time the single photon emission computed tomography (SPECT) findings of a patient with clinically mild encephalitis/encephalopathy with a reversible splenial lesion (MERS) associated with Kawasaki disease, which showed hypoperfusion of the bilateral cingulate gyri, thalamus, basal ganglia, brainstem, and cortex of the frontal lobes. These findings indicate that the pathogenesis of MERS is based on cerebral hypoperfusion due to vasculitis or cerebrovascular dehydration.

Mirror duplication of chromosome 21 with complete phenotype of Down syndrome

© 2008 Japan Pediatric Society The mirror (reverse tandem) duplication of chromosome 21 is a rare chromosomal aberration. Several cases have been described, 1,2 but only a few of them demonstrated chromosome breakpoints in detail using cytogenetic and/or molecular techniques. 2 The Down syndrome critical region (DSCR) is a chromosome 21 segment containing genes responsible for many features of Down syndrome (DS), and is located on 21q22.2 – q22.3. 3,4 We here report a patient with mirror duplication of chromosome 21, whose karyotype was 46,XX, psu idic(21)(q22.3). Clinically, the patient is completely compatible with DS and does not have any fi nding caused by monosomy for 21q22.3 region.

Cardiovascular effects of a phosphodiesterase III inhibitor, amrinone, in infants: Non-invasive echocardiographic evaluation

Objective : The inotropic effect of amrinone is still controversial in management of congestive heart failure in pediatric patients, especially in infants. In order to determine the cardiovascular effect of amrinone in pediatric patients, we performed echocardiographic evaluation in 11 infants (mean age of 2 months) after intracardiac surgery.

Arrhythmia risk and β-blocker therapy in pregnant women with long QT syndrome

Background Pregnancy is one of the biggest concerns for women with long QT syndrome (LQTS). Objectives This study investigated pregnancy-related arrhythmic risk and the efficacy and safety of β-blocker therapy for lethal ventricular arrhythmias in pregnant women with LQTS (LQT-P) and their babies. Methods 136 pregnancies in 76 LQT-P (29±5 years old; 22 LQT1, 36 LQT2, one LQT3, and 17 genotype-unknown) were enrolled. We retrospectively analysed their clinical and electrophysiological characteristics and pregnancy outcomes in the presence (BB group: n=42) or absence of β-blocker therapy (non-BB group: n=94). Results All of the BB group had been diagnosed with LQTS with previous events, whereas 65% of the non-BB group had not been diagnosed at pregnancy. Pregnancy increased heart rate in the non-BB group; however, no significant difference was observed in QT and Tpeak–Tend intervals between the two groups. In the BB group, only two events occurred at postpartum, whereas 12 events occurred in the non-BB group during pregnancy (n=6) or postpartum period (n=6). The frequency of spontaneous abortion did not differ between the two groups. Fetal growth rate and proportion of infants with congenital malformation were similar between the two groups, but premature delivery and low birthweight infants were more common in those taking BB (OR 4.79, 95% CI 1.51 to 15.21 and OR 3.25, 95% CI 1.17 to 9.09, respectively). Conclusions Early diagnosis and β-blocker therapy for high-risk patients with LQTS are important for prevention of cardiac events during pregnancy and the postpartum period, and β-blocker therapy may be tolerated for babies in LQT-P cases.

Lack of an association between E‐selectin gene polymorphisms and risk of Kawasaki disease

Background:  Coronary artery lesions (CAL) are a serious complication of Kawasaki disease (KD). The increased serum E‐selectin level during the acute phase of KD and the association of E‐selectin gene (SELE) polymorphisms with the prevalence of coronary artery disease in adults suggest a possible association between SELE polymorphisms and the development of CAL in KD patients.