Lafora Disease: Molecular Etiology

Lafora Disease (LD) is a fatal neurodegenerative condition characterized by the accumulation of abnormal glycogen inclusions known as Lafora bodies (LBs). Patients with LD manifest myoclonus and tonic-clonic seizures, visual hallucinations, and progressive neurological deterioration beginning at the age of 8-18 years. Mutations in either EPM2A gene encoding protein phosphatase laforin or NHLRC1 gene encoding ubiquitin-ligase malin cause LD. Approximately, 200 distinct mutations accounting for the disease are listed in the Lafora progressive myoclonus epilepsy mutation and polymorphism database. In this review, the genotype-phenotype correlations, the genetic diagnosis of LD, the downregulation of glycogen metabolism as the main cause of LD pathogenesis and the regulation of glycogen synthesis as a key target for the treatment of LD are discussed

De novo 8p23.1 deletion in a patient with absence epilepsy

Çapan Yalçın, Özlem (Arel Author)The 8p23.1 deletion syndrome is a rare multisystem disorder with high penetrance and a variable phenotypic spectrum that includes congenital heart disease (CHD), intellectual disability, behavioural problems, microcephalia, and sometimes epilepsy. Genomic copy number variations (CNVs) constitute an important genetic risk factor for common genetic generalised epilepsy syndromes (GGEs) and absence seizures. These variations, resulting either from copy loss (microdeletion) or copy gain (duplications), disrupt genes associated with neuronal development. Herein, we report an epilepsy patient who was affected by developmental delay, microcephalia, behavioural problems, CHD, and childhood-onset absence seizures. The patient had a 4-Mb de novo microdeletion at 8p23.1. Some of the genes in this region, particularly XKR6 and MIR597, may be involved in the pathogenesis of absence seizures, suggesting that epilepsy may possibly be part of the phenotypic spectrum of the syndrome rather than a comorbid disorder. Thus, CNV screening for GG Eplus patients may have important implications in clinical practice with regards to diagnostic classification, clinical management of the syndromic multisystem disorders, and, potentially, genetic counselling

Genetic alterations and pathways in patients with Hereditary Angioedema of Unknown Cause (U-HAE)

Objective: Hereditary angioedema ( HAE) with normal C1 inhibitor (HAE-nC1-INH), is a genetically complex, rare disease and mutations in F12, ANGPT1, PLG, MYOF genes are found in some families with HAE-nC1-INH. However, often a specific mutation cannot be identified and this type is called as hereditary angioedema of unknown cause (U-HAE). Our aim was to identify putative causative genetic alterations and/or pathways by whole exome sequencing in patients with U-HAE

Functional Characterization of the Type 1 VWD Candidate VWF Gene Variants: P.M771I, p.L881R, p.P1413L, and p.Q1475X

54th Annual Meeting and Exposition of the American-Society-of-Hematology (ASH) --DEC 08-11, 2012 -- Atlanta, GA#nofulltext# --- WOS: 000313838900051…Amer Soc Hematol (ASH

Functional characterisation of the type 1 von Willebrand disease candidate VWF gene variants: p. M771I, p. L881R and p. P1413L

Berber, Ergül (Arel Author), Özbil, Mehmet (Arel Author)Background. Abnormalities in the biosynthetic pathway or increased clearance of plasma von Willebrand factor (VWF) are likely to contribute to decreased plasma VWF levels in inherited type 1 von Willebrand disease (VWD). Recent studies demonstrated that 65% of type 1 VWD patients have candidate VWF mutations, the majority of which are missense variants. The purpose of this study was to explore the effects of three VWF missense mutations (p. M771I, p. L881R and p. P1413L) located in different functional domains of VWF, reported as candidate mutations in type 1 VWD patients in the course of the MCMDM-1VWD study. Materials and methods. The focus of these studies was on the intracellular biosynthetic processing and localisation of VWF in a heterologous cell system. Molecular dynamic simulation for p. M771I and p. P1413L was also performed to analyse the conformational effects of the changes. Results. As determined by immunofluorescence antibody staining and confocal microscopy of HEK293 cells, the intracellular localisation of recombinant VWF with the p. M771I variation was impaired. Transient transfection studies and phorbol myristate acetate stimulation in COS-7 cells revealed significant intracellular retention. In addition, major loss of VWF multimers was observed for only the p. M771I mutation. Molecular dynamic simulations on p. M771I mutant VWF revealed distinct structural rearrangements including a large deviation in the E' domain, and significant loss of beta-sheet secondary structure. Discussion. The pathogenic effects of candidate VWF gene mutations were explored in this study. In vitro expression studies in heterologous cell systems revealed impaired secretion of VWF and a dominant negative effect on the processing of the wild-type protein for only the p. M771I mutation and none of the mutations affected the regulated secretion

Four novel and two recurrent NHLRC1 (EPM2B) and EPM2A gene mutations leading to Lafora disease in six Turkish families

Lafora disease (LD) is a type of autosomal recessive, progressive myoclonus epilepsy resulting mostly from mutations in the EPM2A and NHLRC1 genes. Mutational analysis in both genes was initiated with the aim of establishing LD DNA diagnosis in Turkey. Four novel NHLRC1 (p.G131X, p.P69S and p.D82H) and EPM2A (p.V7A) and two recurrent NHLRC1 (p.D146N) and EPM2A (p.R241X) mutations were identified in six families. The delineation of causative mutations in patients provided early disease diagnosis for other family members and contributed to the knowledge of LD pathogenesis. (C) 2011 Elsevier B.V. All rights reserved

A novel missense mutation (N258S) in the KCNQ2 gene in a Turkish family afflicted with benign familial neonatal convulsions (BFNC)

Benign familial neonatal convulsions (BFNC) is a rare monogenic subtype of idiopathic epilepsy exhibiting autosomal dominant mode of inheritance. The disease is caused by mutations in the two homologous genes KCNQ2 and KCNQ3 that encode the subunits of the voltage-gated potassium channel. Most KCNQ2 mutations are found in the pore region and the cytoplasmic C domain. These mutations are either deletions/insertions that result in frameshift or truncation of the protein product, splice-site variants or missense mutations. This study reveals a novel missense mutation (N258S) in the KCNQ2 gene between the S5 domain and the pore of the potassium channel in two BFNC patients in a Turkish family. The absence of the mutation both in the healthy members of the family and in a control group, and the lack of any other change in the KCNQ2 gene of the patients indicate that N258S substitution is a pathogenic mutation leading to epileptic seizures in this family

A Polymorphism in the IL-5 Gene is Associated with Inhibitor Development in Severe Hemophilia A Patients

OBJECTIVE: A severe complication in the replacement therapy of hemophilia A (HA) patients is the development of alloantibodies (inhibitors) against factor VIII, which neutralizes the substituted factor. The primary genetic risk factors influencing the development of inhibitors are F8 gene mutations. Interleukins and cytokines that are involved in the regulation of B-lymphocyte development are other possible targets as genetic risk factors. This study assesses the possible involvement of 9 selected single nucleotide gene polymorphisms (SNPs) with interleukins (IL-4, IL-5, and IL-10), transforming growth factor beta 1 (TGF-β1), and interferon gamma (IFN-γ) in inhibitor development in severely affected HA patients carrying a null mutation in the F8 gene. METHODS: A total of 173 HA patients were screened for intron 22 inversion and null mutations (nonsense and deletions). Genotyping of a total of 9 SNPs in genes IL-4, IL-5, IL-10, TGF-β1, and IFN-γ in 103 patients and 100 healthy individuals was carried out. RESULTS: An association analysis between 42 inhibitor (+) and 61 inhibitor (-) patients showed a significant association with the T allele of rs2069812 in the IL-5 gene promoter and patients with inhibitors (p=0.0251). The TT genotype was also significantly associated with this group with a p-value of 0.0082, odds ratio of about 7, and confidence interval of over 90%, suggesting that it is the recessive susceptibility allele and that the C allele is the dominant protective allele. CONCLUSION: The lack of other variants in the IL-5 gene of patients and controls suggests that rs2069812 may be a regulatory SNP and may have a role in B-lymphocyte development, constituting a genetic risk factor in antibody development