Macular dystrophy associated with the mitochondrial DNA A3243G mutation: pericentral pigment deposits or atrophy? Report of two cases and review of the literature.

BACKGROUND: The A3243G point mutation in mitochondrial DNA (mtDNA) is associated with MELAS (mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) and MIDD syndromes (maternally inherited diabetes and deafness). Both MELAS and MIDD patients can present with visual symptoms due to a retinopathy, sometimes before the genetic diagnosis is made. CASE PRESENTATION: Patient 1: 46 year-old woman with diabetes mellitus and hearing loss was referred for an unspecified maculopathy detected during screening evaluation for diabetic retinopathy. Visual acuity was 20/20 in both eyes. Fundus examination showed bilateral macular and peripapillary hyperpigmented/depigmented areas.Patient 2: 45 year-old woman was referred for recent vision loss in her left eye. History was remarkable for chronic fatigue, migraine and diffuse muscular pain. Visual acuity was 20/20 in her right eye and 20/30 in her left eye. Fundus exhibited several nummular perifoveal islands of retinal pigment epithelium atrophy and adjacent pale deposits in both eyes.Retinal anatomy was investigated with autofluorescence, retinal angiography and optical coherence tomography. Retinal function was assessed with automated static perimetry, full-field and multifocal electroretinography and electro-oculography. Genetic testing of mtDNA identified a point mutation at the locus 3243. CONCLUSION: Observation of RPE abnormalities in the context of suggestive systemic findings should prompt mtDNA testing.

Identification of the pathological alterations underlying respiratory failure in myotonic dystrophy transgenic mice

AbstractMyotonic dystrophy type 1 (DM1), also known as Steinert's disease, is an inherited autosomal dominant disease. DM1 is characterized by myotonia, muscular weakness and atrophy, but it has a multisystemic phenotype. The genetic basis of the disease is the abnormal expansion of CTG repeats in the 3' untranslated region of the DM protein kinase (DMPK) gene on chromosome 19. The size of the expansion correlates to the severity of the disease and the age of onset.Respiratory problems have long been recognized to be a major feature of the disease and are the main factor contributing to mortality ; however the mechanisms are only partly known. The aim of our study is to investigate whether respiratory failure results only from the involvement of the dystrophic process at the level of the respiratory muscles or comes also from abnormalities in the neuronal network that generates and controls the respiratory rhythm. The generation of valid transgenic mice displaying the human DM1 phenotype by the group of Dr. Gourdon provided us a useful tool to analyze the brain stem respiratory neurons, spinal phrenic motoneurons and phrenic nerves. We examined therefore these structures in transgenic mice carrying 350-500 CTGs and displaying a mild form of the disease (DM1 mice). The morphological and morphometric analysis of diaphragm muscle sections revealed a denervation of the end-plates (EPs), characterized by a decrease in size and shape complexity of EPs and a reduction in the density of acetylcholine receptors (AChRs). Also a strong and significant reduction in the number of phrenic unmyelinated fibers was detected, but not in the myelinated fibers. In addition, no pathological changes were detected in the cervical motoneurons and medullary respiratory centers (Panaite et al., 2008). These results suggest that the breathing rhythm is probably not affected in mice expressing a mild form of DM1, but rather the transmission of action potentials at the level of diaphragm NMJs is deficient.Because size of the mutation increases over generations, new transgenic mice were obtained from the mice with 350-500 CTGs, resulting from a large increase of CTG repeat in successive generations, these mice carry more than 1300 CTGs (DMSXL) and display a severe DM1 phenotype (Gomes-Pereira et al., 2007). Before we study the mechanism underlying the respiratory failure in DMSXL mice, we analyzed the peripheral nervous system (PNS) in these mice by electrophysiological, histological and morphometric methods. Our results provide strong evidence that DMSXL mice have motor neuropathy (Panaite et al., 2010, submitted). Therefore the DMSXL mice expressing severe DM1 features represent for us a good tool to investigate, in the future, the physiological, structural and molecular alterations underlying respiratory failure in DM1. Understanding the mechanism of respiratory deficiency will help to better target the therapy of these problems in DM1 patients. In addition our results may, in the future, orientate pharmaceutical and clinical research towards possible development of therapy against respiratory deficits associated with the DM1.RésuméLa dystrophic myotonique type 1 (DM1), aussi dénommée maladie de Steinert, est une maladie héréditaire autosomique dominante. Elle est caractérisée par une myotonie, une faiblesse musculaire avec atrophie et se manifeste aussi par un phénotype multisystémique. La base génétique de la maladie est une expansion anormale de répétitions CTG dans une région non traduite en 3' du gène de la DM protéine kinase (DMPK) sur le chromosome 19. La taille de l'expansion est corrélée avec la sévérité et l'âge d'apparition de DM1.Bien que les problèmes respiratoires soient reconnus depuis longtemps comme une complication de la maladie et soient le principal facteur contribuant à la mortalité, les mécanismes en sont partiellement connus. Le but de notre étude est d'examiner si l'insuffisance respiratoire de la DM1 est dû au processus dystrophique au niveau des muscles respiratoires ou si elle est entraînée aussi par des anomalies dans le réseau neuronal qui génère et contrôle le rythme respiratoire. La production par le groupe du Dr. Gourdon de souris transgéniques de DM1, manifestant le phénotype de DM1 humaine, nous a fourni un outil pour analyser les nerfs phréniques, les neurones des centres respiratoires du tronc cérébral et les motoneurones phréniques. Par conséquence, nous avons examiné ces structures chez des souris transgéniques portant 350-500 CTG et affichant une forme légère de la maladie (souris DM1). L'analyse morphologique et morphométrique des sections du diaphragme a révélé une dénervation des plaques motrices et une diminution de la taille et de la complexité de la membrane postsynaptîque, ainsi qu'une réduction de la densité des récepteurs à l'acétylcholine. Nous avons aussi détecté une réduction significative du nombre de fibres nerveuses non myélinisées mais pas des fibres myélinisées. Par ailleurs, aucun changement pathologique n'a été détecté pour les neurones moteurs médullaires cervicaux et centres respiratoires du tronc cérébral (Panaite et al., 2008). Ces résultats suggèrent que le iythme respiratoire n'est probablement pas affecté chez les souris manifestant une forme légère du DM1, mais plutôt que la transmission des potentiels d'action au niveau des plaques motrices du diaphragme est déficiente.Comme la taille du mutation augmente au fil des générations, de nouvelles souris transgéniques ont été générés par le groupe Gourdon; ces souris ont plus de 1300 CTG (DMSXL) et manifestent un phénotype sévère du DM1 (Gomes-Pereira et al., 2007). Avant d'étudier le mécanisme sous-jacent de l'insuffisance respiratoire chez les souris DMSXL, nous avons analysé le système nerveux périphérique chez ces souris par des méthodes électrophysiologiques, histologiques et morphométriques. Nos résultats fournissent des preuves solides que les souris DMSXL manifestent une neuropathie motrice (Panaite et al., 2010, soumis). Par conséquent, les souris DMSXL représentent pour nous un bon outil pour étudier, à l'avenir, les modifications physiologiques, morphologiques et moléculaires qui sous-tendent l'insuffisance respiratoire du DM1. La connaissance du mécanisme de déficience respiratoire en DM1 aidera à mieux cibler le traitement de ces problèmes aux patients. De plus, nos résultats pourront, à l'avenir, orienter la recherche pharmaceutique et clinique vers le développement de thérapie contre le déficit respiratoire associé à DM1.

Respiratory failure in a mouse model of myotonic dystrophy does not correlate with the CTG repeat length.

Myotonic dystrophy (DM1) is a multisystemic disease caused by an expansion of CTG repeats in the region of DMPK, the gene encoding DM protein kinase. The severity of muscle disability in DM1 correlates with the size of CTG expansion. As respiratory failure is one of the main causes of death in DM1, we investigated the correlation between respiratory impairment and size of the (CTG)n repeat in DM1 animal models. Using pressure plethysmography the respiratory function was assessed in control and transgenic mice carrying either 600 (DM600) or >1300 CTG repeats (DMSXL). The statistical analysis of respiratory parameters revealed that both DM1 transgenic mice sub-lines show respiratory impairment compared to control mice. In addition, there is no significant difference in breathing functions between the DM600 and DMSXL mice. In conclusion, these results indicate that respiratory impairment is present in both transgenic mice sub-lines, but the severity of respiratory failure is not related to the size of the (CTG)n expansion.

The anticancer drug tamoxifen counteracts the pathology in a mouse model of duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a severe disorder characterized by progressive muscle wasting,respiratory and cardiac impairments, and premature death. No treatment exists so far, and the identification of active substances to fight DMD is urgently needed. We found that tamoxifen, a drug used to treat estrogen-dependent breast cancer, caused remarkable improvements of muscle force and of diaphragm and cardiac structure in the mdx(5Cv) mouse model of DMD. Oral tamoxifen treatment from 3 weeks of age for 15 months at a dose of 10 mg/kg/day stabilized myofiber membranes, normalized whole body force, and increased force production and resistance to repeated contractions of the triceps muscle above normal values. Tamoxifen improved the structure of leg muscles and diminished cardiac fibrosis by~ 50%. Tamoxifen also reduced fibrosis in the diaphragm, while increasing its thickness,myofiber count, and myofiber diameter, thereby augmenting by 72% the amount of contractile tissue available for respiratory function. Tamoxifen conferred a markedly slower phenotype to the muscles.Tamoxifen and its metabolites were present in nanomolar concentrations in plasma and muscles,suggesting signaling through high-affinity targets. Interestingly, the estrogen receptors ERa and ERb were several times more abundant in dystrophic than in normal muscles, and tamoxifen normalized the relative abundance of ERb isoforms. Our findings suggest that tamoxifen might be a useful therapy for DMD.

The TREAT-NMD DMD Global Database: Analysis of More than 7,000 Duchenne Muscular Dystrophy Mutations.

Analyzing the type and frequency of patient-specific mutations that give rise to Duchenne muscular dystrophy (DMD) is an invaluable tool for diagnostics, basic scientific research, trial planning, and improved clinical care. Locus-specific databases allow for the collection, organization, storage, and analysis of genetic variants of disease. Here, we describe the development and analysis of the TREAT-NMD DMD Global database (http://umd.be/TREAT_DMD/). We analyzed genetic data for 7,149 DMD mutations held within the database. A total of 5,682 large mutations were observed (80% of total mutations), of which 4,894 (86%) were deletions (1 exon or larger) and 784 (14%) were duplications (1 exon or larger). There were 1,445 small mutations (smaller than 1 exon, 20% of all mutations), of which 358 (25%) were small deletions and 132 (9%) small insertions and 199 (14%) affected the splice sites. Point mutations totalled 756 (52% of small mutations) with 726 (50%) nonsense mutations and 30 (2%) missense mutations. Finally, 22 (0.3%) mid-intronic mutations were observed. In addition, mutations were identified within the database that would potentially benefit from novel genetic therapies for DMD including stop codon read-through therapies (10% of total mutations) and exon skipping therapy (80% of deletions and 55% of total mutations).

Low penetrance in facioscapulohumeral muscular dystrophy type 1 with large pathological D4Z4 alleles: a cross-sectional multicenter study.

BackgroundFacioscapulohumeral muscular dystrophy type 1(FSHD1) is an autosomal dominant disorder associated with the contraction of D4Z4 less than 11 repeat units (RUs) on chromosome 4q35. Penetrance in the range of the largest alleles is poorly known. Our objective was to study the penetrance of FSHD1 in patients carrying alleles ranging between 6 to10 RUs and to evaluate the influence of sex, age, and several environmental factors on clinical expression of the disease. Methods A cross-sectional multicenter study was conducted in six French and one Swiss neuromuscular centers. 65 FSHD1 affected patients carrying a 4qA allele of 6¿10 RUs were identified as index cases (IC) and their 119 at-risk relatives were included. The age of onset was recorded for IC only. Medical history, neurological examination and manual muscle testing were performed for each subject. Genetic testing determined the allele size (number of RUs) and the 4qA/4qB allelic variant. The clinical status of relatives was established blindly to their genetic testing results. The main outcome was the penetrance defined as the ratio between the number of clinically affected carriers and the total number of carriers. Results Among the relatives, 59 carried the D4Z4 contraction. At the clinical level, 34 relatives carriers were clinically affected and 25 unaffected. Therefore, the calculated penetrance was 57% in the range of 6¿10 RUs. Penetrance was estimated at 62% in the range of 6¿8 RUs, and at 47% in the range of 9¿10 RUs. Moreover, penetrance was lower in women than men. There was no effect of drugs, anesthesia, surgery or traumatisms on the penetrance. Conclusions Penetrance of FSHD1 is low for largest alleles in the range of 9¿10 RUs, and lower in women than men. This is of crucial importance for genetic counseling and clinical management of patients and families.

A founder CEP120 mutation in Jeune asphyxiating thoracic dystrophy expands the role of centriolar proteins in skeletal ciliopathies.

Jeune asphyxiating thoracic dystrophy (JATD) is a skeletal dysplasia characterized by a small thoracic cage and a range of skeletal and extra-skeletal anomalies. JATD is genetically heterogeneous with at least nine genes identified, all encoding ciliary proteins, hence the classification of JATD as a skeletal ciliopathy. Consistent with the observation that the heterogeneous molecular basis of JATD has not been fully determined yet, we have identified two consanguineous Saudi families segregating JATD who share a single identical ancestral homozygous haplotype among the affected members. Whole-exome sequencing revealed a single novel variant within the disease haplotype in CEP120, which encodes a core centriolar protein. Subsequent targeted sequencing of CEP120 in Saudi and European JATD cohorts identified two additional families with the same missense mutation. Combining the four families in linkage analysis confirmed a significant genome-wide linkage signal at the CEP120 locus. This missense change alters a highly conserved amino acid within CEP120 (p.Ala199Pro). In addition, we show marked reduction of cilia and abnormal number of centrioles in fibroblasts from one affected individual. Inhibition of the CEP120 ortholog in zebrafish produced pleiotropic phenotypes characteristic of cilia defects including abnormal body curvature, hydrocephalus, otolith defects and abnormal renal, head and craniofacial development. We also demonstrate that in CEP120 morphants, cilia are shortened in the neural tube and disorganized in the pronephros. These results are consistent with aberrant CEP120 being implicated in the pathogenesis of JATD and expand the role of centriolar proteins in skeletal ciliopathies.

Abrogation of HMX1 function causes rare oculoauricular syndrome associated with congenital cataract, anterior segment dysgenesis, and retinal dystrophy.

PURPOSE: To define the phenotypic manifestation, confirm the genetic basis, and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS). METHODS: Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome-wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling, Western blotting, and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro. RESULTS: Complex developmental ocular abnormalities of congenital cataract, anterior segment dysgenesis, iris coloboma, early-onset retinal dystrophy, and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A>C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function. CONCLUSIONS: Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear, anterior segment, and retina, leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS, enabling the description of only the second family with the condition. HMX1 is a key player in ocular development, possibly in both the pathway responsible for lens and retina development, and via the gene network integral to optic fissure closure.

Identification of two novel mutations in CDHR1 in consanguineous Spanish families with autosomal recessive retinal dystrophy.

Inherited retinal dystrophies present extensive phenotypic and genetic heterogeneity, posing a challenge for patients' molecular and clinical diagnoses. In this study, we wanted to clinically characterize and investigate the molecular etiology of an atypical form of autosomal recessive retinal dystrophy in two consanguineous Spanish families. Affected members of the respective families exhibited an array of clinical features including reduced visual acuity, photophobia, defective color vision, reduced or absent ERG responses, macular atrophy and pigmentary deposits in the peripheral retina. Genetic investigation included autozygosity mapping coupled with exome sequencing in the first family, whereas autozygome-guided candidate gene screening was performed by means of Sanger DNA sequencing in the second family. Our approach revealed nucleotide changes in CDHR1; a homozygous missense variant (c.1720C > G, p.P574A) and a homozygous single base transition (c.1485 + 2T > C) affecting the canonical 5' splice site of intron 13, respectively. Both changes co-segregated with the disease and were absent among cohorts of unrelated control individuals. To date, only five mutations in CDHR1 have been identified, all resulting in premature stop codons leading to mRNA nonsense mediated decay. Our work reports two previously unidentified homozygous mutations in CDHR1 further expanding the mutational spectrum of this gene.

Prise en charge de la candidose oesophagienne en médecine de premier recours [Management of the esophageal candidiasis by the primary care physician].

La candidose oesophagienne est l'une des infections opportunistes les plus fréquentes chez les patients infectés par le VIH. Ce diagnostic se rencontre également chez des patients sans immunodéficience manifeste. Certains facteurs de risque sont également associés à cette pathologie, tels que les traitements corticoïdes systémiques et inhalés ou les traitements par inhibiteurs de la pompe à protons et les antihistaminiques H2. En l'absence de facteur de risque identifié, un déficit immunitaire primaire devrait être recherché. La prévention de la candidose oesophagienne est basée en premier lieu sur l'identification des facteurs de risque, ainsi qu'un meilleur contrôle de ceux-ci. Cet article présente en détail la physio-pathologie, la clinique et la prise en charge par le médecin de premier recours de la candidose oesophagienne. Nous aborderons également les moyens de prévention de la candidose oesophagienne quand il y a lieu. Esophageal candidiasis is one of the most common opportunistic infections in patients infected by human immunodeficiency virus (HIV). This pathology is also found in patients without overt immunodeficiency. Other risk factors are known to be associated with this disease like inhaled or systemic corticosteroid treatment or proton-pump inhibitors and H2 receptor antagonists. In the absence of identified risk factors, a primary immune deficiency should be sought. Prevention of esophageal candidiasis is based primarily on the identification of risk factors, and a better control of them. This article presents a review of the physiopathology, clinical presentation and management of esophageal candidiasis by primary care physicians. We will also discuss ways of preventing esophageal candidiasis when necessary.

A Randomized, Placebo-controlled Trial of Preemptive Antifungal Therapy for the Prevention of Invasive Candidiasis Following Gastrointestinal Surgery for Intra-abdominal Infections.

BACKGROUND: Patients undergoing emergency gastrointestinal surgery for intra-abdominal infection are at risk of invasive candidiasis (IC) and candidates for preemptive antifungal therapy. METHODS: This exploratory, randomized, double-blind, placebo-controlled trial assessed a preemptive antifungal approach with micafungin (100 mg/d) in intensive care unit patients requiring surgery for intra-abdominal infection. Coprimary efficacy variables were the incidence of IC and the time from baseline to first IC in the full analysis set; an independent data review board confirmed IC. An exploratory biomarker analysis was performed using logistic regression. RESULTS: The full analysis set comprised 124 placebo- and 117 micafungin-treated patients. The incidence of IC was 8.9% for placebo and 11.1% for micafungin (difference, 2.24%; [95% confidence interval, -5.52 to 10.20]). There was no difference between the arms in median time to IC. The estimated odds ratio showed that patients with a positive (1,3)-β-d-glucan (ßDG) result were 3.66 (95% confidence interval, 1.01-13.29) times more likely to have confirmed IC than those with a negative result. CONCLUSIONS: This study was unable to provide evidence that preemptive administration of an echinocandin was effective in preventing IC in high-risk surgical intensive care unit patients with intra-abdominal infections. This may have been because the drug was administered too late to prevent IC coupled with an overall low number of IC events. It does provide some support for using ßDG to identify patients at high risk of IC. CLINICAL TRIALS REGISTRATION: NCT01122368.

Role of Myotonic Dystrophy Protein Kinase [DMPK] in Glucose Homeostasis and Muscle Insulin Action

Myotonic dystrophy 1 (DM1) is caused by a CTG expansion in the 3′-unstranslated region of the DMPK gene, which encodes a serine/threonine protein kinase. One of the common clinical features of DM1 patients is insulin resistance, which has been associated with a pathogenic effect of the repeat expansions. Here we show that DMPK itself is a positive modulator of insulin action. DMPK-deficient (dmpk−/−) mice exhibit impaired insulin signaling in muscle tissues but not in adipocytes and liver, tissues in which DMPK is not expressed. Dmpk−/− mice display metabolic derangements such as abnormal glucose tolerance, reduced glucose uptake and impaired insulin-dependent GLUT4 trafficking in muscle. Using DMPK mutants, we show that DMPK is required for a correct intracellular trafficking of insulin and IGF-1 receptors, providing a mechanism to explain the molecular and metabolic phenotype of dmpk−/− mice. Taken together, these findings indicate that reduced DMPK expression may directly influence the onset of insulin-resistance in DM1 patients and point to dmpk as a new candidate gene for susceptibility to type 2-diabetes.

Role of Myotonic Dystrophy Protein Kinase [DMPK] in Glucose Homeostasis and Muscle Insulin Action

Myotonic dystrophy 1 (DM1) is caused by a CTG expansion in the 3′-unstranslated region of the DMPK gene, which encodes a serine/threonine protein kinase. One of the common clinical features of DM1 patients is insulin resistance, which has been associated with a pathogenic effect of the repeat expansions. Here we show that DMPK itself is a positive modulator of insulin action. DMPK-deficient (dmpk−/−) mice exhibit impaired insulin signaling in muscle tissues but not in adipocytes and liver, tissues in which DMPK is not expressed. Dmpk−/− mice display metabolic derangements such as abnormal glucose tolerance, reduced glucose uptake and impaired insulin-dependent GLUT4 trafficking in muscle. Using DMPK mutants, we show that DMPK is required for a correct intracellular trafficking of insulin and IGF-1 receptors, providing a mechanism to explain the molecular and metabolic phenotype of dmpk−/− mice. Taken together, these findings indicate that reduced DMPK expression may directly influence the onset of insulin-resistance in DM1 patients and point to dmpk as a new candidate gene for susceptibility to type 2-diabetes.

Existem diferenças nos parâmetros hematológicos e bioquímicos séricos entre fêmeas normais e portadoras do modelo experimental GRMD (Golden Retriever Muscular Dystrophy)?

A proposta deste estudo foi avaliar se existem alterações nos padrões hematológicos e bioquímicos de cadelas da raça Golden Retriever portadoras do gene da distrofia muscular progressiva em comparação aos valores obtidos em cadelas não portadoras de mesma raça e idade. Foram analisados 33 animais, distribuídos em dois grupos, um composto por 19 cadelas Golden Retrievers não portadoras (GRNP) e outro composto por 14 cadelas Golden Retrievers portadoras do gene da distrofia muscular (GRP). Os dois grupos foram submetidos aos mesmos testes hematológicos e bioquímicos, com a mesma frequência e durante o mesmo intervalo de tempo. Apesar de existir diferença estatisticamente significativa entre os grupos para alguns parâmetros hematológicos avaliados, todos os resultados obtidos estavam de acordo com os valores de referência utilizados. Na avaliação dos parâmetros bioquímicos séricos a dosagem de ALT no grupo GRNP ficou levemente acima da média, porém sem grandes significados clínicos A CK também apresentou níveis elevados no grupo GRP, devido à degeneração e necrose muscular característicos da doença, as alterações encontradas nessa análise já eram esperadas. Os demais parâmetros não se alteraram.

Odonto-ungueal dysplasia: an apparently new autosomal dominant ectodermal dysplasia

We describe 27 subjects (11 women) from five generations of a family with an apparently hitherto undescribed ectodermal dysplasia. All of them presented dental and/or nail alterations only. A genetic analysis of the family suggests an autosomal dominant gene. Differential diagnosis considered eight conditions belonging to the same odonto-onychic (2-3) subgroup, as well as Fried's tooth and nail syndrome and hypodontia and nail dysgenesis (both in 1-2-3 subgroup).