Congenital myopathy with focal loss of cross-striations revisited.

In 1977 Wijngaarden et al. reported a Dutch family with a congenital myopathy characterized by external ophthalmoplegia and a remarkable histological feature, focal loss of cross-striations. A small number of other families with similar clinical and pathological features led to the consideration of this congenital myopathy as a distinct entity. Here we present more than 30years of follow-up from the Dutch family and report recently identified compound heterozygous mutations in the skeletal muscle ryanodine receptor (RYR1) gene, c.10627-2A>G and p.Arg3539His (c.10616G>A). Focal loss of cross-striations on muscle biopsy is another histopathological feature that should raise the possibility of RYR1 involvement.

Recessive RYR1 mutations cause unusual congenital myopathy with prominent nuclear internalization and large areas of myofibrillar disorganization.

AIMS: To report the clinical, pathological and genetic findings in a group of patients with a previously not described phenotype of congenital myopathy due to recessive mutations in the gene encoding the type 1 muscle ryanodine receptor channel (RYR1). METHODS: Seven unrelated patients shared a predominant axial and proximal weakness of varying severity, with onset during the neonatal period, associated with bilateral ptosis and ophthalmoparesis, and unusual muscle biopsy features at light and electron microscopic levels. RESULTS: Muscle biopsy histochemistry revealed a peculiar morphological pattern characterized by numerous internalized myonuclei in up to 51% of fibres and large areas of myofibrillar disorganization with undefined borders. Ultrastructurally, such areas frequently occupied the whole myofibre cross section and extended to a moderate number of sarcomeres in length. Molecular genetic investigations identified recessive mutations in the ryanodine receptor (RYR1) gene in six compound heterozygous patients and one homozygous patient. Nine mutations are novel and four have already been reported either as pathogenic recessive mutations or as changes affecting a residue associated with dominant malignant hyperthermia susceptibility. Only two mutations were located in the C-terminal transmembrane domain whereas the others were distributed throughout the cytoplasmic region of RyR1. CONCLUSION: Our data enlarge the spectrum of RYR1 mutations and highlight their clinical and morphological heterogeneity. A congenital myopathy featuring ptosis and external ophthalmoplegia, concomitant with the novel histopathological phenotype showing fibres with large, poorly delimited areas of myofibrillar disorganization and internal nuclei, is highly suggestive of an RYR1-related congenital myopathy.

Mutational spectrum and phenotypes in Danish families with hereditary angioedema because of C1 inhibitor deficiency.

BACKGROUND: Hereditary angioedema (HAE), type I and II, is an autosomal dominant disease with deficiency of functional C1 inhibitor protein causing episodic swellings of skin, mucosa and viscera. HAE is a genetically heterogeneous disease with more than 200 different mutations in the SERPING1 gene. A genotype-phenotype relationship does not seem to exist in HAE, although the polymorphism c.-21T>C of exon 2 has been reported to be associated with a more severe phenotype. We aimed to establish the mutational spectrum of C1 inhibitor deficiency in Denmark and investigate the possible disease-aggravating effect of the c.-21T>C polymorphism. METHODS: Hereditary angioedema was diagnosed based on clinical features and C1 inhibitor deficiency. A general severity score ranging from 0 to 10 was developed based on age at disease onset, clinical manifestations and treatment experiences. SERPING1 gene investigation was performed by exon sequencing followed by multiplex ligation-dependent probe amplification genomic rearrangement analysis in all known Danish HAE families. RESULTS: Fifty-nine patients with HAE from 26 families were included in this study. The mean disease severity score was 7.12 [1-10], and the mean C1 inhibitor function was 26% [20-46%]. The sensitivity of the mutational screening was 96%, and 13 new mutations were found in this Danish patient cohort. Nine patients (15%) carried the c.-21T>C polymorphism, but they didn't have a more severe phenotype. CONCLUSION: Thirteen new mutations were identified in the Danish HAE population. No correlation between the c.-21T>C polymorphism, the biochemical values of C1 inhibitor function and the clinical severity score was found.

Type III hereditary angio-oedema: clinical and biological features in a French cohort.

BACKGROUND: Hereditary angio-oedema (HAE) has been associated with C1inhibitor deficiency. The first cases of type III HAE were described in patients with normal C1Inh antigenic protein level and function and normal C4 levels in 2000. This finding has been reported mostly in women with a family history and may be influenced by exogenous oestrogen exposure. OBJECTIVES: The purpose of this article is to describe the clinical, biological and genetic characteristics of a French population suffering from type III HAE. PATIENTS AND METHODS: We conducted a retrospective analysis of angio-oedema (AE) cases seen in the National Reference Centre of AE between 2000 and 2009. RESULTS: We found 26 patients (from 15 unrelated families) with type III HAE. All but four were women and presented with typical AE attacks, exacerbated by pregnancy or oral contraceptives containing oestrogens (OC). We also found that 54.5% of women were worsened with oestrogen and 23% were oestrogen dependent. All patients improved on long-term prophylactic tranexamic acid treatment; some acute attacks improved with C1Inh concentrate infusion. All of the patients had normal C1Inh and C4 levels. C1Inh function was also normal, except in women receiving OC or during a pregnancy: transient, moderately low levels (32-74% of the normal range) were found in 18 patients tested (67%). No SERPING1 gene mutation was found. Six patients from three unrelated families were heterozygous for an F12 gene variant. CONCLUSION: Diagnosis of type III HAE should be based on clinical (typical attacks, often hormonally influenced), laboratory (normal C1Inh antigenic protein) and genetic (F12 gene mutation) evidence.

Development and implementation of standardized respiratory chain spectrophotometric assays for clinical diagnosis.

Diversity of respiratory chain spectrophotometric assays may lead to difficult comparison of results between centers. The French network of mitochondrial diseases diagnostic centers undertook comparison of the results obtained with different protocols in the French diagnostic centers. The diversity of protocols was shown to have striking consequences, which prompted the network to undertake standardization and optimization of the protocols with respect to clinical diagnosis, i.e. high velocity while maintaining linear kinetics relative to time and enzyme concentration. Assays were set up on animal tissues and verified on control human muscle and fibroblasts. Influence of homogenization buffer and narrow range of optimal concentration of phosphate, substrate and tissue were shown. Experimental data and proposed protocols have been posted on a free access website. Their subsequent use in several diagnostic centers has improved consistency for all assays.

[Function of aurora kinase C (AURKC) in human reproduction]. / Rôle d'aurora kinase C (AURKC) dans la reproduction humaine.

Infertility concerns at least 70 million couples worldwide. An important proportion of cases is believed to have a genetic component, yet few causal genes have been identified so far. Hundreds of genes are probably involved in spermatogenesis and oogenesis and this genetic heterogeneity has so far hindered the identification of genes causing infertility in the human. Careful morphological examination of spermatozoa can provide cues to identify homogeneous cohorts of patients likely to have the same genetic defect. We studied a cohort of North-Africans patients with a rare phenotype of large-headed spermatozoa. Using a homozygosity mapping strategy, we could map the morbid gene and we identified the same homozygous mutation (c.144delC) in the aurora kinase C gene (AURKC) of all patients studied initially. We then genotyped a total of 62 patients. All who had a typical phenotype with close to 100% large-headed spermatozoa were homozygously mutated (n=34), whereas no AURKC mutations were detected in the others. A carrier frequency of 1/50 was established from individuals from the Maghrebian population, indicating that 1 in 10,000 men from North-African can be expected to present this form of infertility, a frequency comparable to that of Y-microdeletions, thus far the only known recurrent genetic event altering spermatogenesis. Then we demonstrated by flow cytometry that all spermatozoa have in fact a homogeneous 4C. We recommend the realisation of a molecular diagnosis to all patients with large-headed spermatozoa. ICSI is formally contraindicated for all homozygous patients who can have recourse to donor sperm or adoption. One cannot be as categorical for the patients not harbouring an AURKC mutation.

Early onset of hypokalaemic periodic paralysis caused by a novel mutation of the CACNA1S gene.

We report a precocious and atypical form of hypokalaemic periodic paralysis, with clinical manifestations at birth and first episodes of paralysis occurring as early as 1 year of age, although onset of this disease usually occurs between 5-35 years. Extensive molecular analysis showed that the disease was caused by a novel de novo p.Arg897Ser mutation in the CACNA1S gene. The mutation mapped to a new region of the protein, the S4 voltage sensing segment of domain III, at odds with previously reported mutations that exclusively affected domains II and IV.

Muscle imaging in dominant core myopathies linked or unlinked to the ryanodine receptor 1 gene.

OBJECTIVE: To characterize the muscle involvement of patients with central core disease (CCD) caused by mutations in the ryanodine receptor 1 gene (RYR1) and to compare these findings with those from patients with core myopathies unlinked to the RYR1 gene. METHODS: We performed a systematic muscular imaging assessment in 11 patients with an RYR1 gene mutation and compared these findings with those of 5 patients from two unrelated families with autosomal dominant core myopathies not linked to RYR1, ACTA1, or MYH7 gene loci. RESULTS: All patients with RYR1 CCD had a characteristic pattern with predominant involvement of the gluteus maximus, adductor magnus, sartorius, vastus intermediolateralis, soleus, and lateral gastrocnemius muscles. In contrast, muscle CT in the first family not linked to RYR1 showed predominant affection of the gluteus minimus and hamstring muscles, whereas the second family presented with predominant involvement of the gluteus minimus, vastus intermediolateralis, tibialis anterior, and medial gastrocnemius muscles. In addition to muscle imaging data, we present detailed information on the clinical and pathologic findings of these novel phenotypes of core myopathies not linked to RYR1. CONCLUSIONS: Our data suggest genetic heterogeneity in autosomal dominant core myopathies and the existence of additional unidentified genes.

[Molecular genetics of cardiac arrhythmias]. / Génétique moléculaire des arythmies cardiaques.

INTRODUCTION: Recent progress in molecular biology led to the identification of the genes involved in various cardiac arrhythmias causing syncope and sudden death in young people. EXEGESIS: This article briefly describes the clinical features and the genes associated with the congenital long QT syndrome, the short QT syndrome, Brugada's syndrome, catecholaminergic polymorphic ventricular tachycardias and arrhythmogenic right ventricular dysplasia. CONCLUSION: Identification of genetic variations that cause cardiac tachyarrhythmias can help to identify at risk-patients and to propose clinical follow-up and preventive therapy. Further studies are needed to discover other cardiac genetic disorders and to understand cellular mechanisms involved in these diseases.

[Oculo-cerebro-renal Lowe syndrome: clinical, biochemical and molecular studies in a Moroccan patient]. / Syndrome oculo-cérébro-rénal de Lowe: étude clinique, biochimique et moléculaire chez un patient marocain.

The oculo-cerebro-renal syndrome of Lowe is a rare X-linked disorder, caused by the inositol biphosphate 5-phosphatase deficiency, localized to the Golgi complex. Several mutations were reported in patient's OCRL gene leading to enzyme deficiency. We report a Moroccan case of OCRL syndrome of Lowe with a neo mutation in exon 10. The patient aged of 19 months was referred to our medical centre because of a psychomotor retardation. He had a medical history of eye abnormalities including cataract and bilateral glaucoma, diagnosed when he was 5 weeks old. Cataract has been treated after chirurgical therapy but ocular hypertonia persisted. Physical examination revealed an axial hypotonia and walking difficulties. Laboratory tests revealed a moderate acidosis (20 mmol/L), a slight decrease of serum phosphate level (24 mg/L) and an increased serum phosphatase activity. Further studies showed mild proteinuria, urinary bicarbonates loosing and generalised hyperaminoaciduria. Based on both clinical and biological data, Lowe syndrome has been suggested. In this context, molecular investigation has been performed using dHPLC/sequencing techniques which allow identifying an original mutation c.776T>C (p.Phe259Ser), localized on the exon 10 of the OCRL gene. The mutation was not found in the probant's mother suggesting a neo mutation. Lowe syndrome is a rare hereditary X-linked disorder resulting from a variety of heterogeneous mutations of OCRL gene. Indeed, numerous mutations have been reported, variations were noted concerning their localization as well as their type. To our knowledge, this is the first report of the neo mutation c.776T>C of OCRL gene and the first published case report of the Lowe syndrome in a Moroccan patient.

5-lipoxygenase expression and activity in aorta from streptozotocin-induced diabetic rats.

We previously reported an activation of the 5-lipoxygenase pathway in aorta from streptozotocin-induced diabetic rats. The aim of this study was to investigate whether this activation was associated with an increased expression of 5-lipoxygenase, an increased cysteinyl leukotriene (CysLT) production in response to arachidonic acid or calcium ionophore A23187 and/or a hypersensitivity of the aorta to CysLTs in streptozotocin-induced diabetic rats. In aorta from diabetic and control rats, reverse transcriptase-PCR and western blot analysis with a specific 5-lipoxygenase antibody provided evidence for the presence of 5-lipoxygenase in aorta. However, the expression of 5-lipoxygenase was not significantly different between diabetic and control rats. Challenge by A23187 (10 microM) and arachidonic acid (10 microM and 0.1 mM) with or without A23187 (10 micromol/l) induced a significant increase of CysLT release (measured by enzyme immunoassay) that was in the same range in aorta from control and diabetic rats. In contrast, aortas from diabetic rats showed a greater sensitivity to LTC4 and LTD4 contractile effects. These data suggested that the activation of the 5-lipoxygenase pathway previously reported in streptozotocin-induced diabetic rats could be explained by an augmented sensitivity to CysLTs of the diabetic aorta.

Clinical and histopathological aspects of central core disease associated and non-associated with RYR1 locus.

We analysed the clinical, histochemical, ultrastructural and genetic data of patients affected by central core disease (CCD) studied during the last 20 years. From a total series of 86 CCD-families, we have identified 46 CCD families with RYR1 mutations (16 autosomal dominant, 8 autosomal recessive, 17 sporadic cases and 5 de novo mutations). Out of the other 40 CCD families, the RyR1 gene was entirely excluded in 7 families, by cDNA sequencing or linkage analysis, indicating a genetic heterogeneity of CCD.

Prenatal diagnosis of DMD in a female foetus affected by Turner syndrome.

OBJECTIVES: We report on a prenatal diagnosis of DMD complicated by a 45,X karyotype that was revealed only in the chorionic villus long-term culture. METHODS: Cytogenetic investigations were performed on both short-term (STC) and long-term cultures (LTC) of the chorionic villus sample. Familial segregation was performed using a panel of intragenic polymorphic markers, and multiplex PCR was used to characterize exonic deletion. RESULTS: Investigations performed for sex determination after STC of the chorionic villus sample showed a normal karyotype 46,XX, while the karyotype performed after LTC revealed a homogeneous monosomy X. Cytogenetic analysis performed on amniotic fluid cells showed 45,X/46,XX mosaicism. Familial segregation analysis for DMD showed loss of heterozygosity for the STR49 marker in the DNA of the proband, her mother and the foetus. Dystrophin gene analysis on the 45,X cells led to the identification of a deletion of exon 50. CONCLUSIONS: The report described a rare situation of monosomy X associated with a DMD genotype. The data confirmed the DMD carrier status of the proband and her mother and indicated that the foetus had a high risk to combine a Turner phenotype and DMD. This study illustrated the potential risk of using short-term culture of villi as the only source of biological material for prenatal diagnosis.

Comparative analysis of in vitro contracture tests with ryanodine and a combination of ryanodine with either halothane or caffeine: a comparative investigation in malignant hyperthermia.

BACKGROUND: The diagnosis of susceptibility to malignant hyperthermia (MH) is currently performed on muscle biopsies subjected to halothane-caffeine in vitro contracture tests (IVCTs). There is a consensus on our need to improve the diagnostic potential of IVCTs if we are to maximize the information available for research and diagnosis in MH. This study was designed as a pilot comparative study and we aimed at comparing the ryanodine test and new tests using a combination of ryanodine, halothane and caffeine. METHODS: One hundred and thirty-two subjects (52 MHS and 80 MHN) were included in this study and new IVCTs were performed in additional muscle biopsy specimens. The contracture time-course was compared considering the onset time of contracture (OT) and the time to reach a 10 mN contracture (10T). Cut-off values were determined using ROC analyses. RESULTS: For the ryanodine test, sensitivity and specificity calculated for OT were 84.6% and 90.4%, respectively, and were better than those obtained using 10T. Combined tests using either caffeine and ryanodine or halothane and ryanodine did provide higher sensitivities (from 85.3 to 93.9%). A better specificity was only observed for the IVC tests combining halothane (cumulated) and caffeine both with ryanodine (93.9% for both). The largest sensitivity was observed when halothane was used as a bolus and combined with ryanodine. The specificity was always larger with the combined tests as compared to the test using ryanodine alone (from 79.1 to 90.9%). This superiority was confirmed, at least in part, when comparing genetic investigations and the results of new tests in a subgroup of subjects. CONCLUSIONS: This pilot study showed a clear diagnostic potential for new IVC tests combining halothane, the triggering agent of MH, and ryanodine acting at the calcium release channel, and should be considered as a first step in the investigation of combined tests.

[Genetic of diseases by abnormal functioning of the skeletal muscle-calcium releasing complex]. / Génétique des pathologies associées à un dysfonctionnement du complexe de mobilisation calcique du muscle squelettique.

Myoplasmic calcium homeostasis is an essential feature of skeletal muscle contraction. The calcium mobilisation complex (CMC) located at the level of the triadic junction plays a major role for the regulation of calcium fluxes between extra-cellular, cytoplasmic and intra-cellular compartments. The ryanodine receptor type I (RYR1), which is located at the level of the terminal cisternae of the sarcoplasmic reticulum is a key component of the CMC. RYR1 allow the release into the myoplasm of the intralumenal stores of calcium. RYR1 interacts with other proteins: DiHydroPyridine Receptor, triadin, calsequestrin, FKBP12, calmodulin. Malignant hyperthermia (MHS) and congenital core myopathies have been associated with a dysfunction of the CMC. MHS is an autosomic dominant pharmacogenetic disease. The MH crisis is induced by exposure of the predisposed patients to halogenated volatile anaesthetics. MHS is characterised by a genetic heterogeneity and two genes, RYR1 and CACNA1S, have been associated so far with the disease. Mutations in the RYR1 gene have been recently associated with heat stroke, a related syndrome. Central Core Disease (CCD) and Multi minicore Disease (MmD) are congenital myopathies presenting with clinical variability and characterized by the presence of specific although heterogeneous muscle histological features: the cores. Clinical boundaries between the two diseases may overlap and the specific diagnosis is often based on the nature of the cores. These diseases show genetic heterogeneity with both autosomic dominant and recessive mode of inheritance and mutations in the SEPN1, RYR1, ACTA1, TPM3 genes have been reported. Mutations associated with MHS were mainly identified into 2 regions of the N-terminal part of RYR1. Functional role of these two domains is still unclear. Mutations responsible for congenital myopathies mainly mapped to the C terminal region of RYR1 that form the transmembrane calcium channel. Functional studies of the RYR1 mutations have shown that MHS mutations were mainly associated with an alteration of the calcium fluxes in response to caffeine or halothane while CCD mutations would result in a leaky RYR1 channel or would alter the Excitation-Contraction coupling at the level of the CMC.

[Fifty years ago, the double helix gave birth to molecular biology]. / Il y a cinquante ans, la double hélice donnait naissance à la biologie moléculaire.

Fifty years ago, a paper signed by two young scientists, James Watson and Francis Crick, and reporting a model for DNA based on a double helix structure was published in the scientific review Nature in date of april 25, 1953. Although this model of striking simplicity and rare elegance was actually worked out in a few months by the two men, it was the result of quite 100 years of research aimed at the definition of the structure of the genetic material present in living organisms. The double helix was the outcome of a multidisciplinary approach initiated in the mid 19th century by the genetic laws of Gregor Mendel and the discovery of the chemical nature of the desoxyribonucleic acid by Johann Friedrich Miesher. The discovery of the DNA structure had been at the origin of major scientific progress regarding mechanisms that rule the replication and the expression of the genetic information. Theses researches have given birth to a new scientific field, molecular biology, which everyone will see very soon is actually part in a quasi symbiotic manner of all other biological fields dealing with life. The spectacular development of molecular biology during the last fifty years was in great part possible thanks to a concomitant enormous development of the different methods of investigation of the biological molecules and structure. The present rising of biotechnology applications is the direct consequence of the tremendous amount of fundamental knowledge gained during the last few decennia. They open very important and attractive perspectives both on medical or on socio-economic point of views. There is no doubt that the next fifty years will be as fruitful as the last ones.

Toward a characterization of the connecting module of complex I.

Complex I [NADH-ubiquinone oxidoreductase (complex I, EC 1.6.5.3)] couples electron transfer between NADH and ubiquinone to proton transport across the bacterial cytoplasmic membrane and the mitochondrial inner membrane. This sophisticated enzyme consists of three specialized modules: (1) a hydrophilic NADH-oxidizing module that constitutes the input machinery of the enzyme; (2) a hydrophobic module that anchors the enzyme in the membrane and must take part in proton transport; and (3) a connecting domain that links the two previous modules. Using the complex I of Rhodobacter capsulatus, we developed a genetic study of the structure and function of the connecting module. In the present review, we put together the salient results of these studies, with recent reports of the literature, to try and elucidate the structure of the connecting module and its potential role in the coupling process between electron and proton flux within complex I. From this overview, we conclude that the NUOB-NUOD dimer of the connecting module and a hydrophobic subunit such as NUOH must share a quinone-reduction site. The function of this site in the mechanism of complex I is discussed.