Cyprus Institute of Neurology and Genetics

Nicosia, Cyprus

Cyprus Institute of Neurology and Genetics

Nicosia, Cyprus
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Kleopa K.A.,Cyprus Institute of Neurology and Genetics | Abrams C.K.,SUNY Downstate Medical Center | Scherer S.S.,University of Pennsylvania
Brain Research | Year: 2012

The X-linked form of Charcot-Marie-Tooth disease (CMT1X) is the second most common form of hereditary motor and sensory neuropathy. The clinical phenotype is characterized by progressive weakness, atrophy, and sensory abnormalities that are most pronounced in the distal extremities. Some patients have CNS manifestations. Affected males have moderate to severe symptoms, whereas heterozygous females are usually less affected. Neurophysiology shows intermediate slowing of conduction and length-dependent axonal loss. Nerve biopsies show more prominent axonal degeneration than de/remyelination. Mutations in GJB1, the gene that encodes the gap junction (GJ) protein connexin32 (Cx32) cause CMT1X; more than 400 different mutations have been described. Many Cx32 mutants fail to form functional GJs, or form GJs with abnormal biophysical properties. Schwann cells and oligodendrocytes express Cx32, and the GJs formed by Cx32 play an important role in the homeostasis of myelinated axons. Animal models of CMT1X demonstrate that loss of Cx32 in myelinating Schwann cells causes a demyelinating neuropathy. Effective therapies remain to be developed. This article is part of a Special Issue entitled Electrical Synapses. © 2012 Elsevier B.V.

Papageorgiou E.A.,Cyprus Institute of Neurology and Genetics | Karagrigoriou A.,University of Cyprus | Tsaliki E.,Cyprus Institute of Neurology and Genetics | Tsaliki E.,Mitera Hospital | And 4 more authors.
Nature Medicine | Year: 2011

The trials performed worldwide toward noninvasive prenatal diagnosis (NIPD) of Down's syndrome (or trisomy 21) have shown the commercial and medical potential of NIPD compared to the currently used invasive prenatal diagnostic procedures. Extensive investigation of methylation differences between the mother and the fetus has led to the identification of differentially methylated regions (DMRs). In this study, we present a strategy using the methylated DNA immunoprecipitation (MeDiP) methodology in combination with real-time quantitative PCR (qPCR) to achieve fetal chromosome dosage assessment, which can be performed noninvasively through the analysis of fetal-specific DMRs. We achieved noninvasive prenatal detection of trisomy 21 by determining the methylation ratio of normal and trisomy 21 cases for each tested fetal-specific DMR present in maternal peripheral blood, followed by further statistical analysis. The application of this fetal-specific methylation ratio approach provided correct diagnosis of 14 trisomy 21 and 26 normal cases. © 2011 Nature America, Inc. All rights reserved.

Irani S.R.,John Radcliffe Hospital | Pettingill P.,John Radcliffe Hospital | Kleopa K.A.,Cyprus Institute of Neurology and Genetics | Schiza N.,Cyprus Institute of Neurology and Genetics | And 7 more authors.
Annals of Neurology | Year: 2012

Objective: A study was undertaken to describe the clinical spectrum, voltage-gated potassium channel (VGKC) complex antibody specificities, and central nervous system localization of antibody binding in 29 patients diagnosed with Morvan syndrome (MoS). Methods: Clinical data were collected using questionnaires. Radioimmunoassay, cell-based assays, and mouse brain immunohistochemistry were used to characterize the serum antibodies. Results: Neuromyotonia (100%), neuropsychiatric features (insomnia 89.7%, confusion 65.5%, amnesia 55.6%, hallucinations 51.9%), dysautonomia (hyperhidrosis 86.2%, cardiovascular 48.3%), and neuropathic pain (62.1%) were the most common manifestations. A total of 93.1% of MoS patients were male. VGKC-complex antibodies were present in 23 of 29 (79%) MoS patients at referral; 24 of 27 available sera had CASPR2, LGI1, or both CASPR2 and LGI1 antibodies (3 also with contactin-2 antibodies). CASPR2 antibodies were generally higher titer than LGI1 antibodies. Tumors (41.4%), mainly thymomas, were associated with CASPR2 antibodies and a poor prognosis, whereas LGI1 antibodies were associated with serum hyponatremia. In brain tissue regions including the hypothalamus, raphe, and locus coeruleus, commercial antibodies to LGI1 bound to neuronal cell bodies including the antidiuretic hormone-secreting and orexin-secreting hypothalamic neurons, whereas CASPR2 commercial antibodies bound more often to the neuropil. MoS antibodies bound similarly, but there was evidence of additional antibodies in some sera that were not adsorbed by LGI1- or CASPR2-expressing cells and bound to mouse Caspr2 -/- tissue. Interpretation: MoS is clinically distinct from other VGKC-complex antibody-associated conditions, and usually is associated with high-titer CASPR2 antibodies, often accompanied by lower-titer LGI1 antibodies. CASPR2 and LGI1 antibodies bind to multiple brain regions, which helps to explain the multifocal clinical features of this disease, but other antibodies are likely to play a role in some patients and need to be characterized in future studies. Copyright © 2012 American Neurological Association.

Pafiti K.S.,University of Cyprus | Mastroyiannopoulos N.P.,Cyprus Institute of Neurology and Genetics | Phylactou L.A.,Cyprus Institute of Neurology and Genetics | Patrickios C.S.,University of Cyprus
Biomacromolecules | Year: 2011

Four cationic hydrophilic star homopolymers based on the novel hydrophilic, positively ionizable cross-linker bis(methacryloyloxyethyl)methylamine (BMEMA) were synthesized using sequential group transfer polymerization (GTP) and were, subsequently, evaluated for their ability to deliver siRNA to mouse myoblast cells. The nominal degrees of polymerization (DP) of the arms were varied from 10 to 50. For the polymerizations, 2-(dimethylamino)ethyl methacrylate (DMAEMA) was employed as the hydrophilic, positively ionizable monomer. For comparison, four linear DMAEMA homopolymers were also synthesized, whose nominal DPs were the same as those of the arms of the stars. The numbers of arms of the star homopolymers were determined using gel permeation chromatography with static light scattering detection, and found to range from 7 to 19, whereas the hydrodynamic diameters of the star homopolymers in aqueous solution were measured using dynamic light scattering and found to increase with the arm DP from 13 to 26 nm. The presence of the hydrophilic BMEMA cross-linker enabled the solubility of all star homopolymers in pure water. The cloud points of the star homopolymers in aqueous solution increased with the arm DP from 23 to 29°C, while the cloud points of the linear homopolymers were found to decrease with their DP, from 42 to 32°C. The effective pK values of the DMAEMA units were in the range of 6.9 to 7.3 for the star homopolymers, whereas they ranged between 7.3 and 7.4 for the linear homopolymers. Subsequently, all star and linear homopolymers were evaluated for their ability to deliver siRNA to the C2C12 mouse myoblast cell line, expressing the reporter enhanced green fluorescent protein (EGFP). All star homopolymers and the largest linear homopolymer presented significant EGFP suppression, whereas the smaller linear homopolymers were much less efficient. For all star homopolymers and the largest linear homopolymer both the EGFP suppression and the cell toxicity increased with polymer loading. The siRNA-specific EGFP suppression, calculated by subtracting the effect of cell toxicity on EGFP suppression, slightly increased with star polymer loading for the two smaller stars, whereas it presented a shallow maximum and a decrease for the other two stars. Moreover, the siRNA-specific EGFP suppression also increased slightly with the DP of the arms of the DMAEMA star homopolymers. Overall, the EGFP suppression efficiencies with the present star homopolymers were at levels comparable to that of the commercially available transfection reagent Lipofectamine. © 2011 American Chemical Society.

Koutsoulidou A.,Cyprus Institute of Neurology and Genetics | Mastroyiannopoulos N.P.,Cyprus Institute of Neurology and Genetics | Furling D.,University Pierre and Marie Curie | Uney J.B.,University of Bristol | Phylactou L.A.,Cyprus Institute of Neurology and Genetics
BMC Developmental Biology | Year: 2011

Background: MicroRNAs (miRNAs) are small RNA molecules that post-transcriptionally regulate gene expression and have been shown to play an important role during development. miR-1, miR-133a, miR-133b and miR-206 are expressed in muscle tissue and induced during muscle cell differentiation, a process that directs myoblasts to differentiate into mature myotubes, which are organized into myofibers. Although miR-1, miR-133a, miR-133b and miR-206 are well-studied in muscle, there is no information about their expression and function during human development. The purpose of this study was to determine the profile of these miRNAs in muscle cells isolated from different stages of human development. Results: We examined the levels of miR-1, miR-133a, miR-133b and miR-206 during the development of human foetus. All four miRNA levels were found increased during late stages of human foetal muscle development. Increases in the expression levels of these miRNAs were proportional to the capacity of myoblasts to form myotubes. Changes in miRNA levels during human foetal development were accompanied by endogenous alterations in their known targets and also in their inducer, MyoD. Ectopic MyoD expression caused an induction of muscle cell differentiation in vitro, accompanied by an increase in the levels of miR-1, miR-133a, miR-133b and miR-206. Conclusions: This study provides data about the profile of four miRNAs in human muscle cells isolated during different stages of foetal development. These results may shed light on the differentiation of muscle cells and regulation of muscle formation through miRNAs, during the development of human foetus. © 2011 Koutsoulidou et al; licensee BioMed Central Ltd.

Spanaki C.,University of Crete | Zaganas I.,University of Crete | Kleopa K.A.,Cyprus Institute of Neurology and Genetics | Plaitakis A.,University of Crete
Journal of Biological Chemistry | Year: 2010

Mammalian glutamate dehydrogenase (GDH) is an allosterically regulated enzyme that is expressed widely. Its activity is potently inhibited by GTP and thought to be controlled by the need of the cell for ATP. In addition to this housekeeping human (h) GDH1, humans have acquired (via a duplication event) a highly homologous isoenzyme (hGDH2) that is resistant to GTP. Although transcripts of GLUD2, the gene encoding hGDH2, have been detected in human neural and testicular tissues, data on the endogenous protein are lacking. Here, we developed an antibody specific for hGDH2 and used it to study human tissues. Western blot analyses revealed, to our surprise, that endogenous hGDH2 is more densely expressed in testis than in brain. At the subcellular level, hGDH2 localized to mitochondria. Study of testicular tissue using immunocytochemical and immunofluorescence methods revealed that the Sertoli cells were strongly labeled by our anti-hGDH2 antibody. In human cerebral cortex, a robust labeling of astrocytes was detected, with neurons showing faint hGDH2 immunoreactivity. Astrocytes and Sertoli cells are known to support neurons and germ cells, respectively, providing them with lactate that largely derives from the tricarboxylic acid cycle via conversion of glutamate to α-ketoglutarate (GDH reaction). As hGDH2 is not subject to GTP control, the enzyme is able to metabolize glutamate even when the tricarboxylic acid cycle generates GTP amounts sufficient to inactivate the housekeeping hGDH1 protein. Hence, the selective expression of hGDH2 by astrocytes and Sertoli cells may provide a significant biological advantage by facilitating metabolic recycling processes essential to the supportive role of these cells. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

The largest proportion of microRNAs in humans (ca. 40-50%) originated in the phylogenetic grouping defined as primates. The dynamic evolution of this family of non-coding RNA is further demonstrated by the presence of microRNA unique to the human species. Investigations into the role of microRNA in cancer have until recently mainly focused on the more ancient members of this RNA family that are widely conserved in the animal kingdom. As I describe in this review the evolutionary young lineage and species-specific microRNA could be important contributors to cancers, especially in particular organs in primates compared to more distantly-related research models. Elucidating the biological significance of primate and human-specific microRNA in cancer could have important implications for cancer research and the use of non-primate animal models. The human miRNAome can be divided into miRNAs that are widely conserved, those that are primate-specific, and those that are human-specific. The latter two categories can also contribute to tumor development and complicate the study of human cancers in non-primate animal models. © 2016 WILEY Periodicals, Inc.

Tanteles G.A.,Cyprus Institute of Neurology and Genetics | Christophidou-Anastasiadou V.,Cyprus Institute of Neurology and Genetics
Clinical Dysmorphology | Year: 2014

Patient 1, the oldest of the three children, was born to healthy nonconsanguineous parents, a 37-year-old father and a 24-year-old mother. Family history was noncontributory and no known exposure to teratogens was reported. Antenatal scans were normal. She was born following a normal vaginal delivery at term with a birth weight of 3 kg (10th-25th centile), a birth length of 49 cm (25th-50th centile) and a birth occipitofrontal circumference of 33 cm (10th centile). Apgar scores were normal and she did not require any resuscitation. Initial concerns were raised because of poor visual contact. Subsequent ophthalmology assessment revealed bilateral iris and chorioretinal colobomata as well as involvement of the optic nerves. Examination at infancy was significant for distinct facial features (high forehead with frontal bossing, hypertelorism, strabismus, deep set eyes, large uplifted earlobes, prominent nasal tip, prominent columella, open mouth with M-shaped upper lip and a prominent chin). Hypotonia, severe global developmental delay, absent speech and mild to moderate constipation were also recorded. She developed seizures at the age of 11 years. Her facial features coarsened with time, her eyebrows became 'heavier', broad and horizontal with an increased medial separation and sparseness. The columella became more prominent leading to a short philtrum appearance, the face was more elongated and the jaw more pronounced (Fig. 1). Her MRI brain scan was unremarkable, as were an abdominal ultrasound scan and echocardiography. Karyotype and array-comparative genomic hybridization analyses as well as a basic metabolic screen were either normal or negative for abnormalities. Patient 2, the younger of the two children, was born to nonconsanguineous parents, a 31-year-old father and a 29-year-old mother. Review of the family history revealed that the father had unspecified renal problems and proteinuria. The mother enjoyed a good general health. The couple had two first trimester miscarriages in addition to their two live-born offspring. This was the mother's fourth pregnancy. No known exposure to teratogens was reported. Antenatal scans raised the possibility of microphthalmia and hypospadias. He was born following a Caesarean section at 36 weeks gestation with a birth weight of 3 kg (10th-25th centile). Soon after birth, he was transferred to the neonatal ICU because of respiratory distress. Multiple congenital anomalies were noted at the time, which included a perimembranous ventricular septal defect with pulmonary hypertension and a persistent ductus arteriosus that was subsequently ligated, bilateral microphthalmia, a right iris coloboma, left partial aniridia, hypospadias and distinct facial features including hypertelorism, round nasal tip, prominent columella and uplifted earlobes (Fig. 2). Mild hypotonia and developmental delay were subsequently recorded. He developed seizures at the age of 16 months. He had mild to moderate constipation that resolved by the age of 18 months. His MRI brain scan did not reveal any brain malformations. Karyotype analysis and a basic metabolic screen were normal. Array-comparative genomic hybridization analysis revealed a 16q23.2q23.3 deletion of ∼0.265Mb in size. As this deletion was maternally inherited and the clinical evaluation of the mother was unremarkable, it was concluded that it was probably of no clinical significance. © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Markoullis K.,Cyprus Institute of Neurology and Genetics | Sargiannidou I.,Cyprus Institute of Neurology and Genetics | Schiza N.,Cyprus Institute of Neurology and Genetics | Hadjisavvas A.,Cyprus Institute of Neurology and Genetics | And 3 more authors.
Acta Neuropathologica | Year: 2012

Oligodendrocyte gap junctions (GJs) are vital for central nervous system myelination, but their involvement in multiple sclerosis (MS) pathology remains unknown. The aim of this study was to examine alterations of oligodendrocyte and related astrocyte GJs in MS lesions and normal-appearing white matter (NAWM). Post-mortem brain samples from 9 MS and 11 age-matched non-MS control patients were studied. Tissue sections that included both chronic active and inactive lesions were characterized neuropathologically with Luxol Fast Blue staining and immunostaining for myelin oligodendrocyte glycoprotein (MOG) and the microglial marker Iba1. We analyzed the expression of Cx32 and Cx47 in oligodendrocytes and of Cx43, the major astrocytic partner in oligodendrocyte-astrocyte (O/A) GJs by quantitative immunoblot and real-time PCR. Formation of GJ plaques was quantified by immunohistochemistry. Compared to control brains, both Cx32 and Cx47 GJ plaques and protein levels were reduced in and around MS lesions, while Cx43 was increased as part of astrogliosis. In the NAWM, Cx32 was significantly reduced along myelinated fibers whereas Cx47 showed increased expression mainly in oligodendrocyte precursor cells (OPCs). However, OPCs showed only limited connectivity to astrocytes. Cx43 showed modestly increased levels in MS NAWM compared to controls, while GJ plaque counts were unchanged. Our findings indicate that oligodendrocyte GJs are affected not only in chronic MS lesions but also in NAWM, where disruption of Cx32 GJs in myelinated fibers may impair myelin structure and function. Moreover, limited O/A GJ connectivity of recruited OPCs in the setting of persistent inflammation and astrogliosis may prevent differentiation and remyelination. © Springer-Verlag 2012.

Oikonomopoulou K.,Mount Sinai Hospital | Kyriacou K.,Cyprus Institute of Neurology and Genetics | Diamandis E.P.,Mount Sinai Hospital
Clinical Cancer Research | Year: 2013

Several studies have shown that persistent infections and inflammation can favor carcinogenesis. At the same time, certain types of pathogens and antitumor immune responses can decrease the risk of tumorigenesis or lead to cancer regression. Infectious agents and their products can orchestrate a wide range of host immune responses, through which they may positively or negatively modulate cancer development and/or progression. The factors that direct this dichotomous influence of infection-mediated immunity on carcinogenesis are not well understood. Even though not universal, several previous reports have investigated the inverse link of pathogen-induced "benign" inflammation to carcinogenesis and various other pathologies, ranging from autoimmune diseases to allergy and cancer. Several models and ideas are discussed in this review, including the impact of decreased exposure to pathogens, as well as the influence of pathogen load, the timing of infection, and the type of instigated immune response on carcinogenesis. These phenomena should guide future investigations into identifying novel targets within the microbial and host proteome, which will assist in the development of cancer therapeutics and vaccine remedies, analogous to earlier efforts based on helminthic components for the prevention and/or treatment of several pathologies. ©2013 AACR.

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