TRPM4 non-selective cation channel variants in long QT syndrome.

BACKGROUND: Long QT syndrome (LQTS) is an inherited arrhythmic disorder characterized by prolongation of the QT interval, a risk of syncope, and sudden death. There are already a number of causal genes in LQTS, but not all LQTS patients have an identified mutation, which suggests LQTS unknown genes. METHODS: A cohort of 178 LQTS patients, with no mutations in the 3 major LQTS genes (KCNQ1, KCNH2, and SCN5A), was screened for mutations in the transient potential melastatin 4 gene (TRPM4). RESULTS: Four TRPM4 variants (2.2% of the cohort) were found to change highly conserved amino-acids and were either very rare or absent from control populations. Therefore, these four TRPM4 variants were predicted to be disease causing. Furthermore, no mutations were found in the DNA of these TRPM4 variant carriers in any of the 13 major long QT syndrome genes. Two of these variants were further studied by electrophysiology (p.Val441Met and p.Arg499Pro). Both variants showed a classical TRPM4 outward rectifying current, but the current was reduced by 61 and 90% respectively, compared to wild type TRPM4 current. CONCLUSIONS: This study supports the view that TRPM4 could account for a small percentage of LQTS patients. TRPM4 contribution to the QT interval might be multifactorial by modulating whole cell current but also, as shown in Trpm4-/- mice, by modulating cardiomyocyte proliferation. TRPM4 enlarges the subgroup of LQT genes (KCNJ2 in Andersen syndrome and CACNA1C in Timothy syndrome) known to increase the QT interval through a more complex pleiotropic effect than merely action potential alteration.

A systematic variant screening in familial cases of congenital heart defects demonstrates the usefulness of molecular genetics in this field.

The etiology of congenital heart defect (CHD) combines environmental and genetic factors. So far, there were studies reporting on the screening of a single gene on unselected CHD or on familial cases selected for specific CHD types. Our goal was to systematically screen a proband of familial cases of CHD on a set of genetic tests to evaluate the prevalence of disease-causing variant identification. A systematic screening of GATA4, NKX2-5, ZIC3 and Multiplex ligation-dependent probe amplification (MLPA) P311 Kit was setup on the proband of 154 families with at least two cases of non-syndromic CHD. Additionally, ELN screening was performed on families with supravalvular arterial stenosis. Twenty-two variants were found, but segregation analysis confirmed unambiguously the causality of 16 variants: GATA4 (1 ×), NKX2-5 (6 ×), ZIC3 (3 ×), MLPA (2 ×) and ELN (4 ×). Therefore, this approach was able to identify the causal variant in 10.4% of familial CHD cases. This study demonstrated the existence of a de novo variant even in familial CHD cases and the impact of CHD variants on adult cardiac condition even in the absence of CHD. This study showed that the systematic screening of genetic factors is useful in familial CHD cases with up to 10.4% elucidated cases. When successful, it drastically improved genetic counseling by discovering unaffected variant carriers who are at risk of transmitting their variant and are also exposed to develop cardiac complications during adulthood thus prompting long-term cardiac follow-up. This study provides an important baseline at dawning of the next-generation sequencing era.

Extracoronary echocardiographic findings as predictors of coronary artery lesions in the initial phase of Kawasaki disease.

OBJECTIVE: To describe the significance of pericardial effusion (PE), mitral regurgitation (MR) and impaired systolic function in predicting coronary artery lesions (CAL) at diagnosis and follow-up in Kawasaki disease (KD). DESIGN: Echocardiographic records on admission, at 1-3 weeks of illness, and at 6-8 weeks of illness were retrospectively retrieved in children with acute KD treated by intravenous immunoglobulins. SETTING, PATIENTS: The study included 194 consecutive children (113 male; median age 2.1 years) in a paediatric cardiology tertiary care centre, from 1988 to 2007. RESULTS: Overall, children with CAL (64/194) were more likely to have PE (OR=3.00, CI 1.34 to 6.72) and MR (OR=2.51, CI 1.22 to 5.16) at diagnosis; PE was the sole echocardiographic abnormality associated with CAL in multivariable analysis. These abnormalities were predictive of the presence of CAL at the first echocardiography in the acute phase of the disease only. MR, systolic dysfunction and PE were not associated with persistence of CAL in the convalescent phase. Male gender, CAL size and resistance to immunoglobulin treatment were independent factors predictive of the persistence of CAL. CONCLUSIONS: Children with MR or PE should undergo careful assessment of coronary status at diagnosis. However, PE or MR at diagnosis is not predictive of persistent CAL at follow-up.

A de novo mutation of the beta cardiac myosin heavy chain gene in an infantile restrictive cardiomyopathy.

Here we report the first pediatric case of restrictive cardiomyopathy secondary to a de novo mutation in the cardiac myosin heavy chain gene MYH7. The clinical course is characterized by an early onset of disease, mild hypertrophy of the left ventricle and a very short evolution to death. Because of the location of the mutation in the hinge region between the rod part and the globular head of the myosin molecule, it is possible that restrictive cardiomyopathy resulted from an impairment of flexion/extension of myosin heads during the contraction/relaxation cycle.