Impact of brain-derived neurotrophic factor Val66Met polymorphism and response to escitalopram or paroxetine in obsessive-compulsive disorder.

OBJECTIVE: Obsessive-compulsive disorder (OCD) is a severe psychiatric disorder characterized by its heterogeneous nature and by different dimensions of obsessive-compulsive (OC) symptoms. Serotonin reuptake inhibitors (SRIs) are used to treat OCD, but up to 40% to 60% of patients do not show a significant improvement with these medications. In this study, we aimed to test the impact of brain-derived neurotrophic factor (BDNF) Val66Met polymorphism on the efficacy of antidepressants in OCD overall, and in relation to the different OC dimensions. METHODS: In a 6-month prospective treatment study, 69 Caucasian OCD patients were treated with escitalopram for 24 weeks or with escitalopram for 12 weeks followed by paroxetine for an additional 12-week period. Patients were genotyped and assessed for treatment response. The main clinical outcomes were improvement of the Yale-Brown Obsessive-Compulsive Scale score and in different OC symptom dimension scores. RESULTS: The Val/Val group comprised 43 (62%) patients, the Val/Met and Met/Met group comprised 26 (38%) patients. Forty-two patients were classified as responders at 12 weeks and 38 at 24 weeks; no significant association was found between BDNF Val66Met and SRIs response at 12 and 24 weeks. In analyses of the different OC symptom dimensions, the Met allele was associated with a slightly reduced score in the aggressive/checking dimension at 6 months (P = .048). CONCLUSIONS: Our findings do not support the usefulness of BDNF Val66Met genotyping to predict overall response to treatment with SRIs in OCD; they did however suggest a better outcome at 6 months for the aggressive/checking symptom dimension for patients carrying the Met allele.

Sequence variations of ACVRL1 play a critical role in hepatic vascular malformations in hereditary hemorrhagic telangiectasia.

BACKGROUND: Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disorder characterized by multiple telangiectases and caused by germline disease-causing variants in the ENG (HHT1), ACVRL1 (HHT2) and, to a lesser extent MADH4 and GDF2, which encode proteins involved in the TGF-ß/BMP9 signaling pathway. Common visceral complications of HHT are caused by pulmonary, cerebral, or hepatic arteriovenous malformations (HAVMs). There is large intrafamilial variability in the severity of visceral involvement, suggesting a role for modifier genes. The objective of the present study was to investigate the potential role of ENG, ACVRL1, and of other candidate genes belonging to the same biological pathway in the development of HAVMs. METHODS: We selected 354 patients from the French HHT patient database who had one disease causing variant in either ENG or ACVRL1 and who underwent hepatic exploration. We first compared the distribution of the different types of variants with the occurrence of HAVMs. Then, we genotyped 51 Tag-SNPs from the Hap Map database located in 8 genes that encode proteins belonging to the TGF-ß/BMP9 pathway (ACVRL1, ENG, GDF2, MADH4, SMAD1, SMAD5, TGFB1, TGFBR1), as well as in two additional candidate genes (PTPN14 and ADAM17). We addressed the question of a possible genetic association with the occurrence of HAVMs. RESULTS: The proportion of patients with germline ACVRL1 variants and the proportion of women were significantly higher in HHT patients with HAVMs. In the HHT2 group, HAVMs were more frequent in patients with truncating variants. Six SNPs (3 in ACVRL1, 1 in ENG, 1 in SMAD5, and 1 in ADAM17) were significantly associated with HAVMs. After correction for multiple testing, only one remained significantly associated (rs2277383). CONCLUSIONS: In this large association study, we confirmed the strong relationship between ACVRL1 and the development of HAVMs. Common polymorphisms of ACVRL1 may also play a role in the development of HAVMs, as a modifying factor, independently of the disease-causing variants.

Functional and splicing defect analysis of 23 ACVRL1 mutations in a cohort of patients affected by Hereditary Hemorrhagic Telangiectasia.

Hereditary Hemorrhagic Telangiectasia syndrome (HHT) or Rendu-Osler-Weber (ROW) syndrome is an autosomal dominant vascular disorder. Two most common forms of HHT, HHT1 and HHT2, have been linked to mutations in the endoglin (ENG) and activin receptor-like kinase 1 (ACVRL1or ALK1) genes respectively. This work was designed to examine the pathogenicity of 23 nucleotide variations in ACVRL1 gene detected in more than 400 patients. Among them, 14 missense mutations and one intronic variant were novels, and 8 missense mutations were previously identified with questionable implication in HHT2. The functionality of missense mutations was analyzed in response to BMP9 (specific ligand of ALK1), the maturation of the protein products and their localization were analyzed by western blot and fluorescence microscopy. The splicing impairment of the intronic and of two missense mutations was examined by minigene assay. Functional analysis showed that 18 out of 22 missense mutations were defective. Splicing analysis revealed that one missense mutation (c.733A>G, p.Ile245Val) affects the splicing of the harboring exon 6. Similarly, the intronic mutation outside the consensus splicing sites (c.1048+5G>A in intron 7) was seen pathogenic by splicing study. Both mutations induce a frame shift creating a premature stop codon likely resulting in mRNA degradation by NMD surveillance mechanism. Our results confirm the haploinsufficiency model proposed for HHT2. The affected allele of ACVRL1 induces mRNA degradation or the synthesis of a protein lacking the receptor activity. Furthermore, our data demonstrate that functional and splicing analyses together, represent two robust diagnostic tools to be used by geneticists confronted with novel or conflicted ACVRL1 mutations.

Unmasked Brugada pattern by ajmaline challenge in patients with myotonic dystrophy type 1.

BACKGROUND: Myotonic dystrophy type 1 (DM1) generates missplicing of the SCN5A gene, encoding the cardiac sodium channel (Nav 1.5). Brugada syndrome, which partly results from Nav 1.5 dysfunction and causes increased VF occurrence, can be unmasked by ajmaline. We aimed to investigate the response to ajmaline challenge in DM1 patients and its potential impact on their sudden cardiac death risk stratification. METHODS: Among 36 adult DM1 patients referred to our institution, electrophysiological study and ajmaline challenge were performed in 12 patients fulfilling the following criteria: (1) PR interval >200 ms or QRS duration >100 ms; (2) absence of complete left bundle branch block; (3) absence of permanent ventricular pacing; (4) absence of implantable cardioverter-defibrillator (ICD); (5) preserved left-ventricular ejection fraction >50%; and (6) absence of severe muscular impairment. Of note, DM1 patients with ajmaline-induced Brugada pattern (BrP) were screened for SCN5A. RESULTS: In all the 12 patients studied, the HV interval was <70 ms. A BrP was unmasked in three patients but none carried an SCN5A mutation. Ajmaline-induced sustained ventricular tachycardia occurred in one patient with BrP, who finally received an ICD. The other patients did not present any cardiac event during the entire follow-up (15 ± 4 months). CONCLUSION: Our study is the first to describe a high prevalence of ajmaline-induced BrP in DM1 patients. The indications, the safety, and the implications of ajmaline challenge in this particular setting need to be determined by larger prospective studies.

Myotonic dystrophy type 1 mimics and exacerbates Brugada phenotype induced by Nav1.5 sodium channel loss-of-function mutation.

BACKGROUND: Myotonic dystrophy type 1 (DM1), a muscular dystrophy due to CTG expansion in the DMPK gene, can cause cardiac conduction disorders and sudden death. These cardiac manifestations are similar to those observed in loss-of-function SCN5A mutations, which are also responsible for Brugada syndrome (BrS). OBJECTIVE: The purpose of this study was to investigate DM1 effects on clinical expression of a loss-of-function SCN5A mutation causing BrS. METHODS: We performed complete clinical evaluation, including ajmaline test, in 1 family combining DM1 and BrS. We screened the known BrS susceptibility genes. We characterized an SCN5A mutation using whole-cell patch-clamp experiments associated with cell surface biotinylation. RESULTS: The proband, a 15-year-old female, was a survivor of out-of-hospital cardiac arrest with ventricular fibrillation. She combined a DMPK CTG expansion from the father's side and an SCN5A mutation (S910L) from the mother's side. S910L is a trafficking defective mutant inducing a dominant negative effect when transfected with wild-type Nav1.5. This loss-of-function SCN5A mutation caused a Brugada phenotype during the mother's ajmaline test. Surprisingly, in the father, a DM1 patient without SCN5A mutation, ajmaline also unmasked a Brugada phenotype. Furthermore, association of both genetic abnormalities in the proband exacerbated the response to ajmaline with a massive conduction defect. CONCLUSION: Our study is the first to describe the deleterious effect of DM1 on clinical expression of a loss-of-function SCN5A mutation and to show a provoked BrS phenotype in a DM1 patient. The modification of the ECG pattern by ajmaline supports the hypothesis of a link between DM1 and Nav1.5 loss of -function.

The heart rate-lowering agent ivabradine inhibits the pacemaker current I(f) in human atrial myocytes.

INTRODUCTION: It has been speculated that pacemaker current (I(f)) in human atria could play a role in causing ectopic atrial automaticity. Ivabradine is a novel selective and specific I(f) inhibitor in the sinus node that reduces heart rate without any negative inotropic effect. The aim of the study was to explore possible effects of ivabradine on I(f) in atrial myocytes. METHODS AND RESULTS: Using patch-clamp technique, we studied effects of ivabradine on I(f) present in atrial myocytes isolated from human right appendages of patients undergoing cardiac surgery. The identification of HCN isoforms was obtained by means of multiplex single-cell RT-PCR. Ivabradine induced a marked concentration and use-dependent I(f) inhibition with an IC50 at steady state of 2.9 microM. Time constant of block development (Tau(on)) decreases with the increase in the ivabradine concentration. Use-dependent inhibition induced by ivabradine (3 microM) was not modified in the presence of cAMP (10 microM) in the pipette solution. Multiplex single-cell RT-PCR indicates that the major HCN gene subtype detected in atria was HCN2. HCN4 is detected weakly and HCN1 is not significantly detected. CONCLUSIONS: Ivabradine inhibits I(f) current in the nonpacemaker cell with characteristics similar to those described previously in rabbit sinus node cells, but revealed a lesser sensitivity for I(f) recorded in human atrial cell than hHCN4 subunits considered as the major contributors to native f-channels in human sinoatrial node. A potential protection of atrial arrhythmias by ivabradine is discussed.

Mini-dystrophin expression down-regulates overactivation of G protein-mediated IP3 signaling pathway in dystrophin-deficient muscle cells.

We present here evidence for the enhancement of an inositol 1,4,5-trisphosphate (IP3) mediated calcium signaling pathway in myotubes from dystrophin-deficient cell lines (SolC1(-)) as compared to a cell line from the same origin but transfected with mini-dystrophin (SolD(+)). With confocal microscopy, we demonstrated that calcium rise, induced by the perifusion of a solution containing a high potassium concentration, was higher in SolC1(-) than in SolD(+) myotubes. The analysis of amplitude and kinetics of the calcium increase in SolC1(-) and in SolD(+) myotubes during the exposure with SR Ca2+ channel inhibitors (ryanodine and 2-APB) suggested the presence of two mechanisms of SR calcium release: (1) a fast SR calcium release that depended on ryanodine receptors and (2) a slow SR calcium release mediated by IP3 receptors. Detection analyses of mRNAs (reverse transcriptase [RT]-PCR) and proteins (Western blot and immunolocalization) demonstrated the presence of the three known isoforms of IP3 receptors in both SolC1(-) and SolD(+) myotubes. Furthermore, analysis of the kinetics of the rise in calcium revealed that the slow IP3-dependent release may be increased in the SolC1(-) as compared to the SolD(+), suggesting an inhibitory effect of mini-dystrophin in this signaling pathway. Upon incubation with pertussis toxin (PTX), an inhibitory effect similar to that of the IP3R inhibitor (2-APB) was observed on K+-evoked calcium release. This result suggests the involvement of a Gi protein upstream of the IP3 pathway in these stimulation conditions. A hypothetical model is depicted in which both Gi protein and IP3 production could be involved in K+-evoked calcium release as well as a possible interaction with mini-dystrophin. Our findings demonstrate the existence of a potential relationship between mini-dystrophin and SR calcium release as well as a regulatory role of mini-dystrophin on intracellular signaling.

Functional characterization of a Ca(2+)-activated non-selective cation channel in human atrial cardiomyocytes.

Cardiac arrhythmias, which occur in a wide variety of conditions where intracellular calcium is increased, have been attributed to the activation of a transient inward current (Iti). Iti is the result of three different [Ca]i-sensitive currents: the Na(+)-Ca2+ exchange current, a Ca(2+)-activated chloride current and a Ca(2+)-activated non-selective cationic current. Using the cell-free configuration of the patch-clamp technique, we have characterized the properties of a Ca(2+)-activated non-selective cation channel (NSC(Ca)) in freshly dissociated human atrial cardiomyocytes. In excised inside-out patches, the channel presented a linear I-V relationship with a conductance of 19 +/- 0.4 pS. It discriminated poorly among monovalent cations (Na+ and K+) and was slightly permeable to Ca2+ ions. The channel's open probability was increased by depolarization and a rise in internal calcium, for which the Kd for [Ca2+]i was 20.8 microM. Channel activity was reduced in the presence of 0.5 mM ATP or 10 microM glibenclamide on the cytoplasmic side to 22.1 +/- 16.8 and 28.5 +/- 8.6%, respectively, of control. It was also inhibited by 0.1 mM flufenamic acid. The channel shares several properties with TRPM4b and TRPM5, two members of the 'TRP melastatin' subfamily. In conclusion, the NSC(Ca) channel is a serious candidate to support the delayed after-depolarizations observed in [Ca2+] overload and thus may be implicated in the genesis of arrhythmias.