[Show abstract][Hide abstract] ABSTRACT: Brugada syndrome (BrS) is caused mainly by mutations in the SCN5A gene, which encodes the α-subunit of the cardiac sodium channel Na(v)1.5. However, ≈ 20% of probands have SCN5A mutations, suggesting the implication of other genes. MOG1 recently was described as a new partner of Na(v)1.5, playing a potential role in the regulation of its expression and trafficking. We investigated whether mutations in MOG1 could cause BrS.
MOG1 was screened by direct sequencing in patients with BrS and idiopathic ventricular fibrillation. A missense mutation p.Glu83Asp (E83D) was detected in a symptomatic female patient with a type-1 BrS ECG but not in 281 controls. Wild type (WT)- and mutant E83D-MOG1 were expressed in HEK Na(v)1.5 stable cells and studied using patch-clamp assays. Overexpression of WT-MOG1 alone doubled sodium current (I(Na)) density compared to control conditions (P<0.01). In contrast, overexpression of mutant E83D alone or E83D+WT failed to increase I(Na) (P<0.05), demonstrating the dominant-negative effect of the mutant. Microscopy revealed that Na(v)1.5 channels failed to properly traffic to the cell membrane in the presence of the mutant. Silencing endogenous MOG1 demonstrated a 54% decrease in I(Na) density.
Our results support the hypothesis that dominant-negative mutations in MOG1 can impair the trafficking of Na(v)1.5 to the membrane, leading to I(Na) reduction and clinical manifestation of BrS. Moreover, silencing MOG1 reduced I(Na), demonstrating that MOG1 is likely to be important in the surface expression of Na(v)1.5 channels. All together, our data support MOG1 as a new susceptibility gene for BrS.
[Show abstract][Hide abstract] ABSTRACT: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease in which mutations affecting Plakophilin-2 (PKP2) are the most frequently detected. However, pathogenicity of variants is not always fully determined. PKP2 encodes two isoforms, the longest (PKP2b) includes the alternatively spliced exon 6, which is routinely screened for molecular diagnosis, despite the absence of data on cardiac expression of PKP2 isoforms.
To examine the pathogenicity of PKP2 exon 6 mutations by focusing on a missense variant located in this exon.
The PKP2 heterozygous p.Arg490Trp variant was identified in two unrelated ARVC probands (absent from 470 controls). In silico analysis suggested that PKP2 exon 6 is an Alu-derived sequence with very low expression level. PKP2a mRNA, which does not include the sequence encoded by exon 6, was the dominant isoform transcribed; at western blot analysis PKP2A was the only clearly detectable isoform in all human heart samples analysed (from six different controls and the proband). Moreover, in the proband's sample, p.Arg490Trp was not associated with aberrant exon 6 splicing or mutant mRNA downregulation. Finally, a heterozygous missense variant (p.Glu2343Lys) in Desmoplakin was identified in this proband and is likely to be the disease-causing mutation.
PKP2A was shown to be the major isoform expressed in human heart tissue and PKP2B protein was undetectable. The results strongly suggest that p.Arg490Trp and other variants located in PKP2 exon 6 may not be disease causing. Variant splicing also has important consequences for the interpretation of mutation analysis and genetic counselling in ARVC and other hereditary cardiac diseases.
[Show abstract][Hide abstract] ABSTRACT: Five desmosomal genes have been recently implicated in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) but the clinical impact of genetics remains poorly understood. We wanted to address the potential impact of genotyping.
Direct sequencing of the five genes (JUP, DSP, PKP2, DSG2, and DSC2) was performed in 135 unrelated patients with ARVD/C. We identified 41 different disease-causing mutations, including 28 novel ones, in 62 patients (46%). In addition, a genetic variant of unknown significance was identified in nine additional patients (7%). Distribution of genes was 31% (PKP2), 10% (DSG2), 4.5% (DSP), 1.5% (DSC2), and 0% (JUP). The presence of desmosomal mutations was not associated with familial context but was associated with young age, symptoms, electrical substrate, and extensive structural damage. When compared with other genes, DSG2 mutations were associated with more frequent left ventricular involvement (P = 0.006). Finally, complex genetic status with multiple mutations was identified in 4% of patients and was associated with more frequent sudden death (P = 0.047).
This study supports the use of genetic testing as a new diagnostic tool in ARVC/D and also suggests a prognostic impact, as the severity of the disease appears different according to the underlying gene or the presence of multiple mutations.
[Show abstract][Hide abstract] ABSTRACT: Hereditary cardiomyopathy is a primitive disorder in which the heart muscle is structurally and functionally abnormal in the absence of any other cause of cardiomyopathy. They are separated into four phenotypic groups, hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy and arrhythmogenic cardiomyopathy of the right ventricle. Hypertrophic cardiomyopathy was the first identified at the molecular level and then the first to benefit of molecular testing. The molecular analyses were then extended the following years to the dilated cardiomyopathy and restrictive cardiomyopathy. The arrhythmogenic right ventricular cardiomyopathy was the latest to be analyzed at the molecular level because the identification of genes involved in that phenotype was published only in 2002 to 2006. The genetics analysis of these diseases has developed over the past decade and, although still complex, is now available in current hospital practice. The objectives of these tests are to confirm a diagnosis difficult to achieve by classic clinical approach and to perform predictive and presymptomatic diagnosis in families when the mutation was identified. This allows for appropriate care of patients at risk, and may respond to a request for prenatal diagnosis in particularly serious forms. These tests are framed in the context of genetic counselling consultation and patients are the subjects of a multidisciplinary care in reference centres.
[Show abstract][Hide abstract] ABSTRACT: ABSTRACT
Mitochondrial diseases are an important group of genetic diseases caused by respiratory chain dysfunction. The diagnosis is often difficult due to many different clinical manifestations; it relies upon a combination of different approaches including clinical analysis, investigation of the lactate metabolism in vivo (blood and CSF), biochemical measurement of the respiratory chain activities, morphological analyses and molecular studies of mitochondrial and/or nuclear genes. The aim of this retrospective work is to compare the contribution of each investigation in making final diagnosis
Les maladies mitochondriales constituent un ensemble très hétérogène de pathologies dû à un dysfonctionnement de la chaîne respiratoire, dont le diagnostic est difficile à établir devant la présentation clinique et l’augmentation du lactate (sang et/ou LCR), la démarche diagnostique au laboratoire repose sur l’examen anatomopathologique de la biopsie musculaire, puis sur la mesure des activités de la chaîne respiratoire (ASCR) et/ou l’étude par génétique moléculaire de l’ADN mitochondrial (ADNmit) ou de gènes nucléaires impliqués dans cette maladie. L’objectif de ce travail rétrospectif est de comparer l’apport de ces différentes investigations dans le cheminement diagnostique.
Matériel et méthodes : nous avons analysé les résultats obtenus sur les 1962 biopsies musculaires de patients d’âge néonatal à 88 ans [naissance à 2 ans (n=302), 2 à 15 ans (n=305), >15 ans (n=1001)], adressés dans notre centre pour suspicion de maladie mitochondriale, entre 1992 et 2007. Les analyses réalisées étaient la morphologie musculaire (n=1201), la mesure des activités de la chaîne des OXPHOS (ASCR) (n=1221), la recherche de délétion(s) de l’ADNmit par Southern Blot ou PCR longue (n=1029), la recherche de mutations ponctuelles de l’ADNmit par DGGE ou séquençage (n=527), le screening par séquençage de gènes nucléaires impliqués dans la maintenance de l’ADNmit (POLG, DGUOK, TK2,PEO1)
Résultats : 507 patients présentaient des anomalies mitochondriales caractéristiques (Ragged Red Fibers, fibres COX-) ; elles étaient accompagnées de diminution isolée ou combinée des ASCR dans environ 25% des cas ; dans ce groupe de patients, 61 patients sur 372 analysés présentaient une délétion de l’ADNmit tandis que 69 (24%) sur 290 étudiés présentaient une mutation pathogène de l’ADNmit ; parmi les patients présentant des anomalies modérées (n=313) ou ayant une morphologie normale (n=276) une anomalie de l’ADNmit n’était trouvée que chez 20 patients (5 délétions et 15 mutations ponctuelles). Au total, le diagnostic moléculaire a pu être posé pour 304 patients, soit 15% des patients adressés pour suspicion de maladies mitochondriales ; le rendement diagnostique est amélioré dans le groupe des patients avec déficit isolé ou combiné de la chaîne respiratoire (24%) ou avec une morphologie musculaire évocatrice (40%).
Conclusion : ce travail illustre la difficulté du diagnostic biologique des maladies mitochondriales et met en évidence la nécessité de disposer d’une biopsie musculaire dont l’analyse permet de considérablement améliorer le rendement du diagnostic génétique.
[Show abstract][Hide abstract] ABSTRACT: We report the case of a 41-year-old man with a diagnosis of sporadic arrhythmogenic right ventricular cardiomyopathy (ARVC). Genetic screening identified the heterozygous missense mutation R49H in the desmoglein-2 gene. The mutation was absent in both parents, and we demonstrated that it was a de novo mutation. To the best of our knowledge, this is the first description of a de novo mutation in ARVC. This has important implications, including for clinical practice, since individuals with sporadic ARVC caused by a de novo mutation can transmit the disease gene to 50% of their offspring. This suggests that the benefit of molecular genetics can be extended to sporadic ARVC and may improve genetic counselling.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to verify the analytical range of the DIAgam XS Cardio NanoGold C-reactive protein (CRP) method proposed as a full-range assay.
For this purpose, analytical specifications were verified according to the Clinical and Laboratory Standards Institute specifications and a comparison was made with the reference method for the cardiovascular risk assessment, the CardioPhase high sensitivity CRP from Siemens Healthcare Diagnostics.
Our results showed that the immunoturbidimetric assay of CRP using reagents from DIAgam laboratory gave accurate and precise measurements from 0.42 to 265 mg/L. The performances in limits of detection and linearity allowed a full-range determination of CRP concentrations. The comparison with the reference method for the determination of cardiovascular risk was also accurate.
In conclusion, the DIAgam reagents might be used in a routine laboratory for the detection of acute inflammation as well as for evaluation of cardiovascular risk.
Clinical Chemistry and Laboratory Medicine 01/2009; 47(1):109-11. · 3.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cystatin C-based equations are used to estimate GFR. However, three cystatin C immunoassays are on the market. Difference in cystatin C assays could have strong consequences on the accuracy and precision of cystatin C-based equations. We have performed an analytical study of these three assays and studied potential differences between assays on the precision of cystatin C-based equations.
We have studied imprecision, recovery, linearity and interferences of the three immunoassays (nephelometric assay from Siemens and turbidimetric assays from Dako and Gentian). The impact of differences in cystatin C assays has been studied for the equations published by Levey (Siemens assay) and Grubb (Dako assay).
Analytical performance of the Dako assay is slightly less high. For cystatin C values below 2.5 mg/L, no statistical difference is found between results given by the Dako and the Gentian assays. So, both assays can be used in the Grubb equation. Cystatin C results are different with the Siemens assay. The Levey equation, built with the Siemens assay, can only be used with cystatin C values measured with this assay. Using the Dako or Gentian assay results in the Levey equation can lead to differences in estimating GFR up to 6 mL/min/1.73 m2. Differences can reach 9.5 mL/min/1.73 m2 if the Siemens assay is used in the Grubb equation.
The Siemens and Gentian assays seem analytically more valid than the Dako assay for cystatin C determination. Differences in cystatin C assays can lead to significant differences in cystatin C-based equations. However, these differences seem less important than the differences observed with creatinine and creatinine-based equations.
[Show abstract][Hide abstract] ABSTRACT: The distinct cardiac arrhythmia diseases, Brugada syndrome (BS) and isolated cardiac conduction disease (ICCD) are caused by heterozygous mutations in the SCN5A gene. Previous studies have demonstrated an intriguing association between ICCD and BS with the same mutation in the SCN5A gene.
The proband of a multigenerational family presented BS and a familial history of sudden death. We performed clinical evaluations in family members including drug testing and screening for SCN5A mutations. Based on electrocardiogram features, we identified four individuals with BS, two with ICCD and one compatible with both. For five individuals, one with BS and ICCD, three with BS and one with ICCD, we characterized a heterozygous C- to T- mutation at position 4313 (P1438L) in the SCN5A gene. Expression studies of the P1438L mutation showed non-functional channels. The proband's father with the BS phenotype was not a carrier of the new SCN5A mutation.
We report the case of a family with BS and/or ICCD and describe a novel mutation, the P1438L SCN5A mutation. In this family, the occurrence of BS and ICCD could be due to this single mutation but also to the accidental association of both diseases.
[Show abstract][Hide abstract] ABSTRACT: We report on a patient with a severe, rare neonatal form of non-dystrophic myotonia. The patient presented with facial dysmorphism, muscle hypertrophy, severe constipation, psychomotor delay, and frequent cold-induced episodes of myotonia and muscle weakness leading to severe hypoxia and loss of consciousness. Muscle biopsy was non-specific and electromyography revealed intense generalized myotonia. The myotonic episodes improved after introducing oral mexiletine and maintaining room temperature at 28 degrees C. The patient died at 20 months of age following a bronchopulmonary infection. A previously undescribed de novo heterozygous c.3891C > A change, which predicts p.N1297K in the SCN4A gene. Mutations within the voltage-gated sodium channel alpha-subunit gene (SCN4A) have been described in association with several phenotypes including paramyotonia congenita, hyperkalemic or hypokalemic periodic paralysis, and potassium-aggravated myotonias. The cold-sensitive episodes of stiffness followed by weakness suggested the diagnosis of channelopathy in our patient. However, her neonatal onset, the triggering of severe episodes by exposure to modest decreases in temperature, involvement of respiratory muscles with prolonged apnea, early-onset muscle hypertrophy, psychomotor retardation, and fatal outcome are evocative of a distinct clinical subtype. Our observation expands the phenotypic spectrum of sodium channelopathies.
American Journal of Medical Genetics Part A 02/2008; 146(3):380-3. · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gliomas represent 50% of primary brain tumors, and their prognosis remains poor despite the advances in diagnosis and therapeutic strategies. Low grade gliomas (LGG) are infiltrative tumors and they constantly undergo malignant transformation. Metabolic exploration of human gliomas in vivo, in animals and by using cell culture models showed important differences between tumor tissues and normal brain tissues, which can provide new markers for diagnosis, prognosis and therapeutic targets. In this study, energetic and oxidant metabolisms were explored in biopsy extracts of LGG obtained from the centre and the periphery of tumors. Metabolic pattern of these tumors was explored and the differences between the centre and the periphery pointed. Our study showed a metabolic heterogeneity between tumors, with hypermetabolic and hypometabolic profiles. Lactate to pyruvate ratio was>1, suggesting that the energy metabolism in LGG is glycolytic in nature, particularly in the centre of the tumors. Peripheral samples of tumors showed increased glucose consumption and cytochrome c oxidase activity. Lipid peroxidation and catalase activity were also increased in the periphery compared to the centre of tumors. A relationship between the main antioxidant and energy metabolism enzymes activities was observed, suggesting that periphery of tumors is more active metabolically and more resistant to free radical injury.
Annales de biologie clinique 01/2008; 66(2):143-50. · 0.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Hypokalemic periodic paralysis (HOKPP) is characterized by a paralytic form and a myopathic form. The paralytic form is characterized by attacks of reversible flaccid paralysis with concomitant hypokalemia, usually leading to paraparesis or tetraparesis but sparing the respiratory muscles and heart. Acute paralytic crises usually last at least several hours and sometimes days. Some individuals have only one episode in a lifetime; more commonly, crises occur repeatedly: daily, weekly, monthly, or less often. The major triggering factors are carbohydrate-rich meals and rest after exercise; rarely, cold-induced hypokalemic paralysis has been reported. The interval between crises may vary and may be prolonged by preventive treatment with potassium salts or acetazolamide. The age of onset of the first attack ranges from one to 20 years; the frequency of attacks is highest between ages 15 and 35 and then decreases with age. The myopathic form develops in approximately 25% of affected individuals and results in a progressive fixed muscle weakness that begins at variable ages as exercise intolerance predominantly in the lower limbs. It occurs independent of paralytic symptoms and may be the sole manifestation of HOKPP. Individuals with HOKPP are at increased risk for pre- or post-anesthetic weakness and have a risk for malignant hyperthermia that is increased but not as high as that for individuals with true autosomal dominant malignant hyperthermia susceptibility (MHS).
The diagnosis of HOKPP is based on a history of episodes of flaccid paralysis; low serum concentration of potassium (<0.9 to 3.0 mmol/L) during attacks, but not between attacks; the absence of myotonia clinically and on electromyography (EMG) (with the exception of one family with heat-induced myotonia and cold-induced HOKPP); the absence of hyperthyroidism; the absence of dysmorphic traits and cardiac arrhythmias; and a family history consistent with autosomal dominant inheritance. Of all individuals meeting diagnostic criteria for HOKPP, approximately 55%-70% have mutations in CACNA1S and approximately 8%-10% in SCN4A. Molecular genetic testing is clinically available.
Treatment of manifestations: Paralytic crises are treated with oral or IV potassium to normalize the serum concentration of potassium and to shorten the paralytic episode. ECG and blood potassium concentration must be monitored during treatment. Prevention of primary manifestations: Diet low in sodium and carbohydrate and rich in potassium; oral intake of potassium salts; acetazolamide in some individuals. Prevention of secondary complications: Attention to risk factors for malignant hyperthermia. Surveillance: Varies by symptoms and response to preventive treatment; monitoring focuses on frequency, intensity, and duration of weakness attacks. Neurologic examination should focus on muscle strength in the legs to detect permanent weakness associated with myopathy. Agents/circumstances to avoid: Triggers of paralytic attacks including unusually strenuous effort, excess of carbohydrate-rich meals, sweets, alcohol, and glucose infusion. Corticosteroids should be used with care. Evaluation of relatives at risk: When the family-specific mutation is known, molecular genetic testing of at-risk, asymptomatic family members can identify those at risk for unexpected acute paralysis and/or malignant hyperthermia.
HOKPP is inherited in an autosomal dominant manner. Most individuals diagnosed with HOKPP have an affected parent. The proportion of cases caused by a de novo gene mutation is unknown. Offspring of a proband have a 50% risk of inheriting the mutation. Penetrance is about 90% in males and may be as low as 50% in females depending on the causative mutation. Prenatal testing is possible if the disease-causing mutation has been identified in the family; however, requests for prenatal testing for conditions such as HOKPP that do not affect intellect and have some treatment available are not common.
[Show abstract][Hide abstract] ABSTRACT: Congenital long-QT syndrome is a disorder resulting in ventricular arrhythmias and sudden death. The most common forms of the long-QT syndrome, types 1 and 2, are caused by mutations in the potassium-channel genes KCNQ1 and KCNH2, respectively. Although inheritance of the long-QT syndrome is autosomal dominant, female predominance has often been observed and has been attributed to an increased susceptibility to cardiac arrhythmias in women. We investigated the possibility of an unbalanced transmission of the deleterious trait.
We investigated the distribution of alleles for the long-QT syndrome in 484 nuclear families with type 1 disease and 269 nuclear families with type 2 disease, all with fully genotyped offspring. The families were recruited in five European referral centers for the long-QT syndrome. Mutation segregation, sex ratio, and parental transmission were analyzed after correction for single ascertainment.
Classic mendelian inheritance ratios were not observed in the offspring of either female carriers of the long-QT syndrome type 1 or male and female carriers of the long-QT syndrome type 2. Among the 1534 descendants, the proportion of genetically affected offspring was significantly greater than that expected according to mendelian inheritance: 870 were carriers of a mutation (57%), and 664 were noncarriers (43%, P<0.001). Among the 870 carriers, the allele for the long-QT syndrome was transmitted more often to female offspring (476 [55%]) than to male offspring (394 [45%], P=0.005). Increased maternal transmission of the long-QT syndrome mutations to daughters was also observed, possibly contributing to the excess of female patients with autosomal dominant long-QT syndrome.
Positive selection of the mutated alleles that cause the long-QT syndrome leads to transmission distortion, with increased proportions of mutation carriers among the offspring of affected families. Alleles for the long-QT syndrome are more often transmitted to daughters than to sons.
New England Journal of Medicine 12/2006; 355(26):2744-51. · 51.66 Impact Factor