Theodoros Kyriakides

Mutations in the Dystrophin-Associated Protein γ-Sarcoglycan in Chromosome 13 Muscular Dystrophy

Severe childhood autosomal recessive muscular dystrophy (SCARMD) is a progressive muscle-wasting disorder common in North Africa that segregates with microsatellite markers at chromosome 13q12. Here, it is shown that a mutation in the gene encoding the 35-kilodalton dystrophin-associated glycoprotein, γ-sarcoglycan, is likely to be the primary genetic defect in this disorder. The human γ-sarcoglycan gene was mapped to chromosome 13q12, and deletions that alter its reading frame were identified in three families and one of four sporadic cases of SCARMD. These mutations not only affect γ-sarcoglycan but also disrupt the integrity of the entire sarcoglycan complex.

A comprehensive analysis of the epidemiology and clinical characteristics of anti-LRP4 in myasthenia gravis.

Double-seronegative myasthenia gravis (dSN-MG, without detectable AChR and MuSK antibodies) presents a serious gap in MG diagnosis and understanding. Recently, autoantibodies against the low-density lipoprotein receptor-related protein 4 (LRP4) have been identified in several dSN-MG sera, but with dramatic frequency variation (∼2-50%). We have developed a cell based assay (CBA) based on human LRP4 expressing HEK293 cells, for the reliable and efficient detection of LRP4 antibodies. We have screened about 800 MG patient sera from 10 countries for LRP4 antibodies. The overall frequency of LRP4-MG in the dSN-MG group (635 patients) was 18.7% but with variations among different populations (range 7-32.7%). Interestingly, we also identified double positive sera: 8/107 anti-AChR positive and 10/67 anti-MuSK positive sera also had detectable LRP4 antibodies, predominantly originating from only two of the participating groups. No LRP4 antibodies were identified in sera from 56 healthy controls tested, while 4/110 from patients with other neuroimmune diseases were positive. The clinical data, when available, for the LRP4-MG patients were then studied. At disease onset symptoms were mild (81% had MGFA grade I or II), with some identified thymic changes (32% hyperplasia, none with thymoma). On the other hand, double positive patients (AChR/LRP4-MG and MuSK/LRP4-MG) had more severe symptoms at onset compared with any single positive MG subgroup. Contrary to MuSK-MG, 27% of ocular dSN-MG patients were LRP4 antibody positive. Similarly, contrary to MuSK antibodies, which are predominantly of the IgG4 subtype, LRP4 antibodies were predominantly of the IgG1 and IgG2 subtypes. The prevalence was higher in women than in men (female/male ratio 2.5/1), with an average disease onset at ages 33.4 for females and 41.9 for males. Overall, the response of LRP4-MG patients to treatment was similar to published responses of AChR-MG rather than to MuSK-MG patients.

A novel NF-L mutation Pro22Ser is associated with CMT2 in a large Slovenian family

Abstract. Charcot-Marie-Tooth (CMT) disease is the most-common form of inherited motor and sensory neuropathy. The autosomal dominant axonal form of the disease (CMT2) is currently subdivided into seven types based on genetic localization. These are CMT2A (1p35-p36), CMT2B (3q13-q22), CMT2C (unknown), CMT2D (7p14), CMT2E (8p21), HMNSP (3q13.1), and CMT2F (7q11-q21). Two loci have thus far been identified for autosomal recessive CMT2; ARCMT2A (1q21.1-q21.3) and ARCMT2B (19q13.3). Mutations in four genes (connexin 32, myelin protein zero, neurofilament-light, and kinesin) have been associated with the CMT2 phenotype. We identified a novel neurofilament-light missense mutation (C64T) that causes the disease in a large Slovenian CMT2 family. This novel mutation shows complete co-segregation with the dominantly inherited CMT2 phenotype in our family.

EFNS guidelines on the diagnostic approach to pauci- or asymptomatic hyperCKemia

Objective:  To provide evidence‐based guidelines to general neurologists for the assessment of patients with pauci‐ or asymptomatic hyperCKemia.

Phenotypic and cellular expression of two novel connexin32 mutations causing CMT1X

Objective: To determine the phenotypic and cellular expression of two novel connexin32 (Cx32) mutations causing X-linked Charcot–Marie–Tooth disease (CMT1X). Methods: The authors evaluated several members of two families with CMT1X clinically, electrophysiologically, pathologically, and by genetic testing. The Cx32 mutations were expressed in vitro and studied by immunocytochemistry. Results: In both families, men were more severely affected than women with onset in the second decade of life. In the first family, the phenotype was that of demyelinating polyneuropathy with variable involvement of peripheral nerves. There was clinical evidence of CNS involvement in at least three of the patients, with extensor plantar responses and brisk reflexes. In the second family, the affected man presented with symmetric polyneuropathy and intermediate slowing of conduction velocities, whereas affected women had prominent asymmetric atrophy of the leg muscles. The authors identified two novel missense mutations resulting in L143P amino acid substitution in the first family and in V140E substitution in the second family, both located in the third transmembrane domain of Cx32. Expression of these Cx32 mutations in communication-incompetent HeLa cells and immunocytochemical analysis revealed that both mutants were retained intracellularly and were localized in the Golgi apparatus. In contrast to wild-type protein, they did not form gap junctions. Conclusion: These novel connexin32 (Cx32) mutations cause a spectrum of clinical manifestations characteristic of Charcot–Marie–Tooth disease (CMT1X), including demyelinating or intermediate polyneuropathy, which is often asymmetric, and CNS involvement in one family. The position and cellular expression of Cx32 mutations alone cannot fully predict these phenotypic variations in CMT1X.

Complement C1Q polymorphisms modulate onset in familial amyloidotic polyneuropathy TTR Val30Met.

BACKGROUND Familial amyloidotic polyneuropathy (FAP) TTR Val30Met is a lethal autosomal dominant sensorimotor and autonomic neuropathy due to a substitution of methionine for valine at position 30 of the transthyretin (TTR) gene. Amyloid, composed of mutated TTR, is deposited in the peripheral nervous system, myocardium and kidneys. Considerable variability in the age of onset and penetrance of the disease occurs in different countries. Penetrance in Sweden, Cyprus and Portugal is 2%, 28% and 80% respectively. Environmental and genetic factors are believed to contribute to this variability. So far, no single modifier gene has been unequivocally associated with age of onset or penetrance. METHODS Candidate modifier genes were chosen from among those coding for chaperone proteins co-localized with TTR deposits in peripheral nerves. Seventy one TTRVal30Met carriers, 51 affected and 20 asymptomatic, belonging to 22 unrelated Greek-Cypriot families, and 59 normal controls were recruited for this study. Sequencing of the coding regions of TTR, serum amyloid P (APCS) and complement C1Q (A, B and C) genes was performed and APOE genotypes were determined. We searched for correlations between various polymorphisms of chaperone proteins and age of disease onset. RESULTS Four new and 4 previously described single nucleotide substitutions were identified. One polymorphic site in C1QA (rs172378) and one in C1QC (rs9434) as well as the epsilon2 allele correlated with age of onset (p<0.05). CONCLUSIONS Our study has identified polymorphisms which may influence the FAP-TTR Val30Met phenotype. Identifying modifier genes and their protein products may contribute to therapeutic advances.

Epidemiological, clinical and genetic study of familial amyloidotic polyneuropathy in Cyprus

Objectives. To define the incidence and prevalence of familial amyloidotic polyneuropathy (FAP) TTRVal30Met on the island of Cyprus. To study the clinical phenotype and genetic features of FAP TTRVal30Met in the Cypriot population. Methods. The clinical and neurogenetic databases were used to identify probands with FAP TTRVal30Met and detailed family trees were constructed. Potential carriers of the mutation were identified from the family trees and assessed clinically and genetically. Transthyretin was completely sequenced in patients and potential carriers. Results. Thirty-six patients carrying the TTRVal30Met mutation (one homozygote) from 22 families were identified. On 1 December 2003 the prevalence of FAP was 3.72/100,000 while the incidence is estimated to be 0.69/100,000 per year. The phenotype observed was characteristic for a length dependent sensorimotor and autonomic neuropathy with neuropathic pain. Mean age of onset was 46 years. Penetrance is estimated to be 28% and positive anticipation in the age of onset is found. Conclusion. FAP is relatively prevalent in Cyprus which may be considered as another endemic focus of the disease in Europe. The mean age of onset and penetrance is different from the Portuguese and Swedish populations. Understanding the biological factors that determine these differences could potentially lead to therapeutic advances.

Reversible inflammatory and vacuolar myopathy with vitamin E deficiency in celiac disease

We report a patient with late‐onset celiac disease and neurological manifestations including myopathy, polyneuropathy, and ataxia. Laboratory investigations showed anti‐gliadin antibodies and severe vitamin E deficiency. Muscle biopsy revealed inflammatory infiltrates and rimmed vacuoles, similar to those found in inclusion‐body myositis. A gluten‐free diet and vitamin E supplementation reversed both the clinical neurological manifestations and the abnormalities in the muscle biopsy. Anti‐gliadin antibodies were no longer present. This case illustrates the spectrum of neurological complications of celiac disease and documents the occurrence of reversible pathology resembling inclusion‐body myopathy in the muscle. Muscle Nerve 2004

Charcot-Marie-Tooth Disease in Cyprus: Epidemiological, Clinical and Genetic Characteristics

Background: Charcot-Marie-Tooth disease (CMT) is the most common inherited neuropathy. CMT is classified into 2 main subgroups: a demyelinating and an axonal type. Further subdivisions within these 2 main categories exist and intermediate forms have more recently been described. Inheritance can be autosomal dominant, recessive or X-linked. CMT is associated with more than 30 loci, and about 25 causative genes have been described thus far. Methods: We studied epidemiological, clinical and genetic characteristics of CMT in the Cypriot population. Results: The prevalence of CMT in Cyprus on January 15, 2009, is estimated to be 16 per 100,000. Thirty-three families and 8 sporadic patients were ascertained. CMT was demyelinating in 52%, axonal in 33% and intermediate in 15% of the patients. Thirteen families had PMP22 duplication, 3 families had the PMP22 S22F mutation, 4 families had GJB1/Cx32 mutations, 2 families had different MPZ mutations, 1 of them novel, and 2 families had different MFN2 mutations. Nine families and 8 sporadic patients were excluded from the common CMT genes. Conclusion: The most frequent CMT mutation worldwide, the PMP22 duplication, is also the most frequent CMT mutation in the Cypriot population. Five out of the 8 other mutations are novel, not reported in other populations.

Malignant mutation in the lamin A/C gene causing progressive conduction system disease and early sudden death in a family with mild form of limb-girdle muscular dystrophy

BackgroundLamin proteins A and C are major functional and structural components of the nuclear lamina. Mutations of the LMNA gene have been associated with dilated cardiomyopathy, conduction system defects and skeletal muscle dystrophy simultaneously, in variable involvement. We report on a family with a mutation of the lamin A/C gene (c.908–909delCT).MethodsThirty five members of the family of a proband were studied and underwent clinical and genetic evaluation. Family members were considered to be affected if they demonstrated conduction system defects, limb-girdle muscular dystrophy, dilated cardiomyopathy, carried the lamin A/C mutation or suffered sudden death.ResultsFifteen members of the family were considered to be affected. Conduction system defects were the major feature of the affected members (67%), with variable involvement of dilated cardiomyopathy (33%), and limb-girdle muscular dystrophy (53%). Sudden death occurred in four members (27%) and was the presenting feature in three (20%) of the affected members at an early age. Mutation c.908–909delCT was confirmed in 12 of the affected members. The pattern of inheritance was autosomal dominant.ConclusionLamin c.908–909delCT mutation is malignant compared to other dilated cardiomyopathy—associated mutations of the Lamin A/C gene. Patients with this mutation have rapid progression of atrioventricular conduction abnormalities, and sudden death may be the presenting feature. Early identification of affected families and consideration of an implantable defibrillator is important in this setting.