Mehmet Seven

Zeynep Kamil Women's and Children's Disease Training and Research Hospital, İstanbul, Istanbul, Turkey

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Publications (36)66.26 Total impact

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    ABSTRACT: Cancer is still one of the dominating causes of deaths worldwide, although there have been important enhancements for detection and diagnosis of cancer recently. miRNAs are shown to participate in carcinogenesis of several types of tumors and their aberrant expression of miRNAs has been detected in cell lines, xenografts and clinical samples. miRNAs are thought to target and modulate the expression of more than 60% of human genes, which makes the expressional regulation by miRNAs the most abundant post-transcriptional regulation mode. Here, we have reviewed the most current literature to shed a light on the functions of miRNAs on human carcinogenesis. Possible roles of miRNAs in oncogenesis through both genetic and epigenetic changes occurring during cancer initiation, progression, invasion or metastasis are summarized.
    Future oncology (London, England). 05/2014; 10(6):1027-48.
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    ABSTRACT: CLP1 is a RNA kinase involved in tRNA splicing. Recently, CLP1 kinase-dead mice were shown to display a neuromuscular disorder with loss of motor neurons and muscle paralysis. Human genome analyses now identified a CLP1 homozygous missense mutation (p.R140H) in five unrelated families, leading to a loss of CLP1 interaction with the tRNA splicing endonuclease (TSEN) complex, largely reduced pre-tRNA cleavage activity, and accumulation of linear tRNA introns. The affected individuals develop severe motor-sensory defects, cortical dysgenesis, and microcephaly. Mice carrying kinase-dead CLP1 also displayed microcephaly and reduced cortical brain volume due to the enhanced cell death of neuronal progenitors that is associated with reduced numbers of cortical neurons. Our data elucidate a neurological syndrome defined by CLP1 mutations that impair tRNA splicing. Reduction of a founder mutation to homozygosity illustrates the importance of rare variations in disease and supports the clan genomics hypothesis.
    Cell 04/2014; 157(3):636-50. · 31.96 Impact Factor
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    ABSTRACT: Dyggve-Melchior-Clausen syndrome (DMC) (MIM #223800) is a rare autosomal-recessive type of skeletal dysplasia accompanied by variable degrees of intellectual disability (ID). It is characterized by progressive spondyloepimetaphyseal dysplasia leading to disproportionate short stature, microcephaly, and coarse facies. The radiographic appearance of generalized platyspondyly with double-humped end plates and the lace-like appearance of iliac crests are pathognomonic in this syndrome. The disorder results from mutations in the dymeclin (DYM) mapped to the 18q12-12.1 chromosomal region. Here, we report two cases with DMC: one with disproportionate short stature, developmental delay, and severe ID with a novel frameshift mutation (c.1028_1056del29) leading to a premature stop codon, and the second patient with classical clinical and radiological features of DMC with mild ID and rectal prolapse, which is very rare. The clinical diagnosis was confirmed with molecular analysis of DYM with a known mutation at c.580C>T (p.R194X). The parents and sibling of the second patient were heterozygous carriers with mild skeletal changes and short stature.
    Clinical dysmorphology 01/2014; 23(1):1-7. · 0.47 Impact Factor
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    ABSTRACT: Despite the availability of several antiepileptic drugs, drug resistance remains one of the major challenges in epilepsy therapy. Genetic factors are known to play a significant role in the prognosis and treatment of epilepsy. The aim of this study was to determine the frequencies of alleles for CYP2C9, CYP2C19, and CYP2D6 genes in Turkish children with epilepsy, and to investigate the relationship between the genetic polymorphism of these genes with multiple drug resistance in epilepsy patients. We genotyped 132 epileptic patients (60 drug resistant and 72 drug responsive) and 55 healthy controls for six single nucleotide polymorphisms (SNPs) in CYP2C9, CYP2C19, and CYP2D6. Genotype, allele, and haplotype frequencies were compared between groups. The frequencies of CYP2C9*3/*3 genotype and CYP2C9*3 allele, and the haplotype CCGG (CYP2C9*2 C>T, CYP2C9*3 A>C, and CYP2C19*2 G>A, CYP2C19* G>A) were significantly higher in drug-resistant versus -responsive patients. Our results demonstrated the important role of the CYP2C9*3 allelic variant in preventing epilepsy patients from developing drug resistance. These data suggest that CYP2C9, CYP2C19, and CYP2D6 SNPs and haplotypes may affect the response to antiepileptic drugs.
    Molecular diagnosis & therapy. 12/2013;
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    ABSTRACT: One-third of all individuals with epilepsy are resistant to antiepileptic drug (AED) treatment. Antiepileptic treatment response has been suggested to be modulated by genetic polymorphisms of drug efflux transporters. Several polymorphic variants within the multidrug resistance 1 (MDR1) gene, which encodes the major transmembrane efflux transporter P-glycoprotein, have been proposed to be associated with AED resistance in epilepsy patients. The aim of this study was to evaluate the effect of C3435T and G2677T/A polymorphisms of MDR1 on AED resistance in Turkish children with epilepsy. MDR1 C3435T and G2677T/A were genotyped in 152 patients with epilepsy, classified as drug-resistant in 69 and drug-responsive in 83. Genotypes of the C3435T and G2677T/A polymorphisms were determined by polymerase chain reaction followed by restriction fragment length polymorphism. Genotype and allele frequencies of C3435T and G2677T/A polymorphisms of the MDR1 gene did not differ between drug-resistant and drug-responsive epilepsy patients. Our results suggest that MDR1 C3435T and G2677T/A polymorphisms are not associated with AED resistance in Turkish epileptic patients. To clarify the exact clinical implication of the MDR1 polymorphisms on the multidrug resistance in epilepsy, further investigations in various ethnic populations would be necessary.
    Molecular Biology Reports 11/2013; · 2.51 Impact Factor
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    ABSTRACT: Craniofrontonasal syndrome (CFNS, MIM #304110) is a rare X-linked dominant developmental disorder that shows paradoxically greater severity in affected females than in affected males. Our female patient with frontonasal dysplasia, craniosynostosis and additional malformations was consistent with CFNS. EFNB1, which encodes a member of the ephrin family of transmembrane ligands for Eph receptor tyrosine kinases, is the only gene in which mutation is known to cause CFNS. Here, we describe 402T>C, a novel de novo mutation on EFNB1. This mutation results in substitution of highly conserved isoleucine at 134th residue to threonine.
    Gene 07/2013; · 2.20 Impact Factor
  • Clinical dysmorphology 01/2013; · 0.47 Impact Factor
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    Clinical dysmorphology 11/2012; · 0.47 Impact Factor
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    ABSTRACT: PURPOSE: The accumulation of free radicals may lead to seizures and increase the risk of their recurrence. Glutathione peroxidase and superoxide dismutase are 2 major enzymes that are involved in antioxidative defense mechanisms. Selenium (Se), zinc (Zn), and copper (Cu) are important trace elements that participate in the structure of these enzymes. The purpose of this study was to evaluate the possible associations between trace elements and idiopathic intractable epilepsy (IIE) by comparing the levels of Se, Zn, and Cu between patients with IIE and healthy children. METHODS: Our study was designed as a case-control study with 70 IIE patients and 60 healthy children who were matched for age, ethnicity, and socioeconomic status. The levels of serum Se, Zn, and Cu were measured with an atomic absorption spectrophotometer. The results were statistically analyzed with SPSS version 16.0. KEY FINDINGS: We found that the patients with IIE had significantly decreased levels of serum Se and Zn compared to those of the control group (p<0.05). SIGNIFICANCE: We believe that this study presents the first reports of decreased levels of Se and Zn in patients with IIE. These results may provide new insights for delineating the etiological basis of IIE and its potential therapeutic options.
    Epilepsy research 10/2012; · 2.48 Impact Factor
  • Genetic counseling (Geneva, Switzerland) 01/2012; 23(1):81-5. · 0.32 Impact Factor
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    ABSTRACT: We report a case with a new syndrome that presents with glaucoma, cryptorchidism, oculocutaneous albinism, ataxia, hypotonia, autistic behaviour besides various major and minor craniofacial dysmorphic, skeletal, and neuroimaging findings, and suggest that this case represents a new syndrome not reported previously.
    Genetic counseling (Geneva, Switzerland) 01/2011; 22(1):25-34. · 0.32 Impact Factor
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    ABSTRACT: A 25-year-old female was referred for short stature and joint deformities. Except for previous corneal transplantation, her medical history was unremarkable. Initial physical examination revealed the presence of a coarse facies, short neck, kyphosis, restricted joint movements and deformities, and cardiac murmur besides a normal intellect. Urine glycosaminoglycan levels were high, and blood enzyme assay indicated significantly low alpha-L-iduronidase levels. Mucopolysaccharidosis I (MPS I) was diagnosed and prompted the onset of enzyme replacement therapy (ERT), which significantly improved articular complaints, while cardiac pathology remained stable. At the eighteenth month of ERT, sudden vision loss developed. She spontaneously recovered her vision in a month. MPS I is a progressive disease, in which tissue accummulation of heparan and dermatan sulphate result from defective activity or lack of alpha-L-iduronidase. ERT in MPS I usually presents favourable outcomes or at least stabilization of symptoms. This present case qualifies as the first report ofa MPS I patient developing sudden vision loss under ERT. We suggest that further research studies are warranted for defining the efficiency and possible limitations of ERT.
    Genetic counseling (Geneva, Switzerland) 01/2011; 22(4):371-6. · 0.32 Impact Factor
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    ABSTRACT: Three brothers, born to parents who were first cousins, were referred for progressive diffuse dystonia. Initial physical examinations revealed minor dysmorphic features, e.g., bifrontal narrowing, downslanting palpebral fissures, low-set ears, upturned nostrils, and microretrognathia, as well as neurodevelopmental delay. Absence of eye contact and head control, diffuse dystonia, hypokinesia, choreoathetosis, tremor, increased deep tendon reflexes, diffuse muscle atrophy, and spasticity were evident during neurologic evaluations. After laboratory investigations, imaging studies, and the exclusion of other causes of childhood dystonia, the children were diagnosed with Segawa syndrome. A molecular analysis of the tyrosine hydroxylase gene revealed a novel P492R (1475 C>G) mutation, further confirming the clinical diagnosis. After 1-month therapy with 2 mg/kg/day l-dopa, no changes in signs were evident. Selegiline was added, which greatly improved the clinical picture. Segawa syndrome in three brothers resulted from a novel mutation in the tyrosine hydroxylase gene. Treatment with a combination of l-dopa and selegiline led to favorable outcomes.
    Pediatric Neurology 05/2010; 42(5):348-50. · 1.42 Impact Factor
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    ABSTRACT: Oxidative stress seems to be an important factor in the development of age-related macular degeneration (AMD). The role of DNA repair mechanisms has also received attention recently in AMD pathogenesis. This case-control study was conducted to determine the frequency of polymorphisms in two DNA repair enzyme genes, xeroderma pigmentosum complementation group D (XPD), codons 312 and 751, and x-ray cross-complementing group 1 (XRCC1), codons 194 and 399, in patients with AMD and in disease-free control subjects. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) were used to analyze XPD Asp312Asn and Lys751Gln and XRCC1 Arg194Trp and Arg399Gln in 120 patients with AMD (65 with dry type and 55 with wet type) and in age-matched 205 disease-free control subjects. Genotypic and allelic distributions of the polymorphisms were detected. For the XPD polymorphism, although the allele frequencies were not different between the patients and healthy control subjects, there was a significant difference between frequencies for the XPD751 Gln/Gln genotype in AMD patients (9%) and healthy control subjects (19%; P=0.02). The XPD751 Gln/Gln genotype seemed to have a protective effect against development of AMD (odds ratio, 0.41; 95% confidence interval, 0.19-0.88). Stratification by subtype of AMD revealed that the XPD751 Gln/Gln genotype was significantly lower only in the patients with dry type (P=0.02). These interactions remained nearly significant after Bonferroni correction (P<0.0125). Haplotype analysis for the two XPD polymorphisms revealed that the haplotype GC (312Asp-(751)Gln) was a protective haplotype against AMD. No statistically significant difference was found for the genotypic and allelic distributions of the polymorphisms in the XRCC1 gene between the patients and the control subjects. Polymorphism in XPD codon 751 may be associated with the development of AMD.
    Investigative ophthalmology & visual science 04/2010; 51(9):4732-7. · 3.43 Impact Factor
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    ABSTRACT: We report a 4-year-old Turkish boy with Warburg Micro syndrome born to consanguineous parents. He had ptosis, deep-set eyes, microphthalmia, microcornea, microcephaly, prominent ears and nasal root, micrognathia, hypertrichosis, spastic diplegia, skin hyperextensibility and joint hypermobility, hypogenitalism, cerebral atrophy and hypoplasia of corpus callosum and cerebellum. Sequence analysis of exon 8 of the RAB3GAP gene has confirmed the presence of a splice donor mutation (748+1G>A) in the homozygous state. Skin hyperextensibility and joint hypermobility in the affected child have not been reported in Warburg Micro syndrome cases to date. This report compares the symptoms and features of the case with previously reported cases of Warburg Micro syndrome.
    Clinical Dysmorphology 04/2007; 16(2):89-93. · 0.38 Impact Factor
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    ABSTRACT: Leigh syndrome is an inherited, progressive neurodegenerative disorder of infancy and childhood. Mutations in the nuclear SURF-1 gene are specifically associated with cytochrome C oxidase-deficient Leigh syndrome. This report describes two patients with similar facial features. One of them was a 2(1/2)-year-old male, and the other was a 3-year-old male with a mutation in SURF-1 gene and facial dysmorphism including frontal bossing, brachycephaly, hypertrichosis, lateral displacement of inner canthi, esotropia, maxillary hypoplasia, hypertrophic gums, irregularly placed teeth, upturned nostril, low-set big ears, and retrognathi. The first patient's magnetic resonance imaging at 15 months of age indicated mild symmetric T2 prolongation involving the subthalamic nuclei. His second magnetic resonance imaging at 2 years old revealed a symmetric T2 prolongation involving the subthalamic nuclei, substantia nigra, and medulla lesions. In the second child, at the age of 2 the first magnetic resonance imaging documented heavy brainstem and subthalamic nuclei involvement. A second magnetic resonance imaging, performed when he was 3 years old, revealed diffuse involvement of the substantia nigra and hyperintense lesions of the central tegmental tract in addition to previous lesions. Facial dysmorphism and magnetic resonance imaging findings, observed in these cases, can be specific findings in Leigh syndrome patients with cytochrome C oxidase deficiency. SURF-1 gene mutations must be particularly reviewed in such patients.
    Pediatric Neurology 07/2006; 34(6):486-9. · 1.42 Impact Factor
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    ABSTRACT: The anti-epileptic drug vigabatrin was developed as an inhibitor of gamma-aminobutyric acid transaminase, and its ability to increase inhibition in the central nervous system led to its testing in an animal model. In animal models chronic use of vigabatrin is associated with irreversible myelin vacuolation. Antioxidant drugs change the antioxidant capacity of the body. Oxidative stress of the body increased when valproic acid and carbamazepine were used chronically. To assess whether vigabatrin may affect protein oxidation and lipid peroxidation, glutathione, glutathione peroxidase (GPx), and glutathione-S-transferase (GST) levels were studied in the livers of 57 rat fetuses after administration of vigabatrin to the mothers (19 in the first week of pregnancy, 20 in the second week, and 18 in the third week) and in 19 control rat fetuses without vigabatrin. We compared the results of administration of vigabatrin in each group with the controls. Rat fetus protein oxidation in group I (0.686 nmol/mg protein) and group II (0.723 nmol/mg protein) was higher than in the control group (0.388 nmol/mg protein). Lipid peroxidation (0.209, 0.224, 0.253 nmol/mg protein, respectively) and GPx levels (345.4, 329.0, 283.2 nmol/mg protein, respectively) of groups I, II, and III were higher than in the control group (0.104, 167.2 nmol/mg protein, respectively). GST in group II (79.2 nmol/mg protein) and group III (77.8 nmol/mg protein) were not different from that in the control group (78 nmol/mg protein). It was found that vigabatrin affected all the parameters that were studied, especially in group I, which was given the drug in the first week of pregnancy.
    Drug metabolism and drug interactions 02/2005; 21(2):109-15.
  • M Seven, A Ozkiliç, A Yüksel
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    ABSTRACT: Infantile neuroaxonal dystrophy (INAD) is an autosomal recessive, neurodegenerative disease with onset in the first or second year of life. It has been reported that INAD shows numerous phenotype characteristics including problems associated with vision, hearing and physical coordination. It has however been very rare to see facial dysmorphism in these children. The study analyzes a girl and boy of a first cousin marriage with infantile neuroaxonal dystrophy affected at birth. At infancy, the children were examined in the Cerrahpaşa Medical Faculty Genetic Research Center, Istanbul. They had typical INAD features such as the lack of head control, vision, speech, sitting, and walking which are also seen in children with other congenital abnormalities. These children showed remarkable dysmorphism in the face which included prominent forehead, strabismus, small nose, fish mouth (boy), micrognathia, and large and low-settled ears. The presence of these facial features makes the patients appear unique and diagnosis more accurate. While these features are commonly seen diagnosis may be difficult at its onset. Until now this appearence has not been reported in INAD patients. In conclusion, in the first few months of life without any clinical or neurological signs, the physician should also consider diagnosing the disease of the infant as INAD.
    Genetic counseling (Geneva, Switzerland) 02/2002; 13(4):465-73. · 0.32 Impact Factor
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    ABSTRACT: A 1-year-old female child with multiple dysmorphic features including microcephaly, hypertelorism, a short philtrum, low set ears, a narrow high arched palate, micrognathia and growth retardation was found to have a de novo chromosome abnormality including a partial duplication of the short arm of chromosome 2 and a partial deletion of the long arm of chromosome 17. The clinical features of the case shared many similarities to previous reports of trisomy 2p. Three years later, ecchymotic spots appeared around the left ocular region. Further clinical and pathological examination confirmed the diagnosis of a neuroblastoma. This is the first case of an unbalanced translocation, 46, XX, der (17), t (2; 17) (p23; q25), showing the development of a neuroblastoma in addition to the dysmorphic features. We suggest that trisomy 2p including the N-myc proto-oncogene may have predisposed the patient to the development of a neuroblastoma.
    Clinical Dysmorphology 02/2002; 11(1):39-42. · 0.38 Impact Factor
  • M Cengiz, M Seven, N Suyugül
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    ABSTRACT: Recent studies show a relationship between oxidants, antioxidants, and degenerative disease of aging like cataract formation. Focal lens cortical changes and cortical liquification have been reported in patients with Down syndrome (DS) over 14 years. There is evidence supporting the hypothesis that trisomy 21 patients have an increase in free radical reactions. These changes in antioxidant system may play a role in cataractogenesis in Down syndrome. We screened serum samples from 12 patients with DS and cataract: and 12 healthy age and sex-matched persons. We evaluated the antioxidant enzyme activities of superoxide dismutase (SOD), glutathione peroxidase (GSHPx), glutathione-S-transferase (GST) and reduced glutathione (GSH) in erythrocytes. SOD and GSHPx levels of patients with DS were significantly higher than the control group. No significant changes were observed in GST and GSH levels between the DS and control groups. These findings suggest impairment in antioxidant system, which may be a possible mechanism for early cataract formation in DS.
    Genetic counseling (Geneva, Switzerland) 02/2002; 13(3):339-42. · 0.32 Impact Factor

Publication Stats

187 Citations
66.26 Total Impact Points

Institutions

  • 2014
    • Zeynep Kamil Women's and Children's Disease Training and Research Hospital
      İstanbul, Istanbul, Turkey
  • 1998–2013
    • Istanbul University
      • • Department of Family Medicine (Cerrahpasa Faculty of Medicine)
      • • Department of Medical Genetics
      • • Department of Pathology (Cerrahpasa Faculty of Medicine)
      İstanbul, Istanbul, Turkey
  • 2012
    • Bezmiâlem Vakif Üniversitesi
      İstanbul, Istanbul, Turkey
  • 2002
    • Baskent Üniversitesi Adana Uygulama ve Arastirma Merkezi
      İstanbul, Istanbul, Turkey
  • 2001
    • Turgut Özal University
      İnönü, Sivas, Turkey