Arda Cetinkaya

A Homozygous Deletion in GRID2 Causes a Human Phenotype With Cerebellar Ataxia and Atrophy

GRID2 is a member of the ionotropic glutamate receptor family of excitatory neurotransmitter receptors. GRID2 encodes the glutamate receptor subunit delta-2, selectively expressed in cerebellar Purkinje cells. The phenotype associated with loss of GRID2 function was described only in mice until now, characterized by different degrees of cerebellar ataxia and usually relatively mild abnormalities of the cerebellum. This work describes for the first time the human phenotype associated with homozygous partial deletion of GRID2 in 3 children in one large consanguineous Turkish family. Homozygous deletion of exons 3 and 4 of GRID2 (94 153 589-94 298 037 bp) in the proband and similarly affected cousins, and heterozygous deletions in parental DNA were shown using Affymetrix® 6.0 single-nucleotide polymorphism array, confirmed by real-time polymerase chain reaction. The phenotype includes nystagmus, hypotonia with marked developmental delay in gross motor skills in early infancy followed by a static encephalopathy course with development of cerebellar ataxia, oculomotor apraxia, and pyramidal tract involvement.

The effect of colchicine on pyrin and pyrin interacting proteins.

MEFV which encodes pyrin, cause familial Mediterranean fever (FMF), the most common auto‐inflammatory disease. Pyrin is believed to be a regulator of inflammation, though the nature of this regulatory activity remains to be identified. Prophylactic treatment with colchicine, a microtubule toxin, has had a remarkable effect on disease progression and outcome. It has been thought that, inhibition of microtubule polymerization is the main mechanism of action of colchicine. But, the exact cellular mechanism explaining the efficacy of colchicine in suppressing FMF attacks is still unclear. Given the ability of colchicine treatment to be considered as a differential diagnosis criteria of FMF, we hypothesized that colchicine may have a specific effect on pyrin and pyrin interacting proteins. This study showed that colchicine prevents reticulated fibrils formed by PSTPIP1 filaments and reduces ASC speck rates in transfected cells. We further noted that, colchicine down‐regulates MEFV expression in THP‐1 cells. We also observed that colchicine causes re‐organization of actin cytoskeleton in THP‐1 cells. Pyrin is an actin‐binding protein that specifically localizes with polymerizing actin filaments. Thus, MEFV expression might be affected by re‐organization of actin cytoskeleton. The data presented here reveal an important connection between colchicine and pyrin which might explain the remarkable efficacy of colchicine in preventing FMF attacks. J. Cell. Biochem. 113: 3536–3546, 2012.

Etiological yield of SNP microarrays in idiopathic intellectual disability.

Intellectual disability (ID) has a prevalence of 3% and is classified according to its severity. An underlying etiology cannot be determined in 75-80% in mild ID, and in 20-50% of severe ID. After it has been shown that copy number variations involving short DNA segments may cause ID, genome-wide SNP microarrays are being used as a tool for detecting submicroscopic copy number changes and uniparental disomy. This study was performed to investigate the presence of copy number changes in patients with ID of unidentified etiology. Affymetrix(®) 6.0 SNP microarray platform was used for analysis of 100 patients and their healthy parents, and data were evaluated using various databases and literature. Etiological diagnoses were made in 12 patients (12%). Homozygous deletion in NRXN1 gene and duplication in IL1RAPL1 gene were detected for the first time. Two separate patients had deletions in FOXP2 and UBE2A genes, respectively, for which only few patients have recently been reported. Interstitial and subtelomeric copy number changes were described in 6 patients, in whom routine cytogenetic tools revealed normal results. In one patient uniparental disomy type of Angelman syndrome was diagnosed. SNP microarrays constitute a screening test able to detect very small genomic changes, with a high etiological yield even in patients already evaluated using traditional cytogenetic tools, offer analysis for uniparental disomy and homozygosity, and thereby are helpful in finding novel disease-causing genes: for these reasons they should be considered as a first-tier genetic screening test in the evaluation of patients with ID and autism.

Loss-of-Function Mutations in ELMO2 Cause Intraosseous Vascular Malformation by Impeding RAC1 Signaling

Vascular malformations are non-neoplastic expansions of blood vessels that arise due to errors during angiogenesis. They are a heterogeneous group of sporadic or inherited vascular disorders characterized by localized lesions of arteriovenous, capillary, or lymphatic origin. Vascular malformations that occur inside bone tissue are rare. Herein, we report loss-of-function mutations in ELMO2 (which translates extracellular signals into cellular movements) that are causative for autosomal-recessive intraosseous vascular malformation (VMOS) in five different families. Individuals with VMOS suffer from life-threatening progressive expansion of the jaw, craniofacial, and other intramembranous bones caused by malformed blood vessels that lack a mature vascular smooth muscle layer. Analysis of primary fibroblasts from an affected individual showed that absence of ELMO2 correlated with a significant downregulation of binding partner DOCK1, resulting in deficient RAC1-dependent cell migration. Unexpectedly, elmo2-knockout zebrafish appeared phenotypically normal, suggesting that there might be human-specific ELMO2 requirements in bone vasculature homeostasis or genetic compensation by related genes. Comparative phylogenetic analysis indicated that elmo2 originated upon the appearance of intramembranous bones and the jaw in ancestral vertebrates, implying that elmo2 might have been involved in the evolution of these novel traits. The present findings highlight the necessity of ELMO2 for maintaining vascular integrity, specifically in intramembranous bones.

A Diagnosis to Consider in Intellectual Disability: Mowat-Wilson Syndrome.

Mowat-Wilson syndrome is a multiple congenital anomaly and intellectual disability syndrome characterized by a unique face and various other structural and functional anomalies. The condition is caused by de novo heterozygous mutations or deletions in ZEB2 gene located at 2q22. ZEB2 encodes Sip1 protein, which acts during central nervous system development as an important transcription factor. Herein, we report on 3 novel mutations in 6 patients with the syndrome, with an overview of corresponding clinical findings. Growth retardation and Hirschsprung disease were less common in the present cohort. One patient with a novel mutation p.Y489X had no associated anomalies except the characteristic facial and neurobehavioral phenotype. Reporting new patients with novel mutations would contribute to better delineation of the syndrome and would help clinicians establish formal diagnostic criteria and genotype-phenotype correlations.

Neuropsychological correlates of ADRA2A(rs1800544) and COMT(rs4680) polymorphisms in Turkish ADHD patients

Introduction The complex etiology of ADHD has a strong genetic component. ADRA2A (rs1800544) and COMT (rs4680) polymorphisms are two of the most studied gene polymorphisms in ADHD etiology. However, there is still debate about their indication ofcreating different neuropsychological phenotypes in ADHD.In this study, we aimed to investigate the effects of these polymorphisms on neuropsychological traits among Turkish ADHD patients. Also, the relationship between ADHD symptoms, subtypes and neuropsychological test variables were studied. Methods To examine the phenotypic discrepencies of these genotypes, Continuous Performance Test(CPT) and Trail Making Tests (TMTA-TMTB) were conducted for 121 genotyped ADHD patients between 6-18 years old. Omission- commission errors and mean response time were used as CPT variables. Besides this, completing times, errors and corrections were the variables recorded for TMTA and TMTB. Mental retardation was excluded with Wechsler Intelligence Scale for Children-4 (WISC4)/Wechsler Intelligence Scale for Children –Revised (WISC-R) in the study. Diagnosis and subtype discrimination were confirmed and comorbidities except learning and disruptive behaviour disorders were excluded by using the Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS). Clinical Global Impression –Severity Scale (CGI-S) documented clinical severity, whereas Global Assesment of Functioning Scale (GAS) stated clinical functionality. Conners’ Parent (CPRS) and Teacher Rating Scales (CTRS) were used for determining ADHD symptoms and severity. The statistical analyses were conducted with SPSS 21.0. Mann-Whitney U, Kruskal–Wallis, Spearman correlation tests were used and p Results No relationship was detected between ADRA2A,COMT polymorphisms and CPT,TMT variables. CPT commission errors were found more frequent in the combined subtype, while TMTA corrections were more seen in the inattentive subtype.The learning problem subscale of CPRS and hyperactivity, behaviour problem subscales of CTRS were found associated with CPT commission errors. The hyperactivity, oppositional behaviour subscales of CPRS were related to TMTA errors and corrections whereas behaviour problem subscale of CPRS was only associated with TMTA corrections. The hyperactivity and behaviour problem subscales of CTRS were found correlated with TMTA completing time, errors and corrections. Only attention deficiency subscale of CTRS was found associated both with TMTA corrections and TMTB completing time and errors. CPT parameters were found associated with neither clinical severity nor functioning.However, low clinical functionality ( Conclusions ADRA2A and COMT polymorphisms were not found to be associated with a specific neuropsychological phenotype. While CPT did not predict clinical severity or functioning, longer TMT completing time and more TMT corrections were found associated with lower functionality. Although the results of neuropsychological tests were in accordance with ADHD subtypes, neuropsychological traits did not differ in a homogeneous manner in ADHD patients. Consequently, instead of using the neuropsychological traits in distinguishing groups, they may be helpfully used for supporting clinical evaluation in ADHD. In addition, further studies with whole genome sequencing technics are warrented to better understand the role of polymorphisms in ADHD etiology.

Dermal fibroblast transcriptome indicates contribution of wnt signaling pathways in the pathogenesis of apert syndrome

Çetinkaya A, Taşkıran E, Soyer T, Şimşek-Kiper PÖ, Utine GE, Tunçbilek G, Boduroğlu K, Alikaşifoğlu M. Dermal fibroblast transcriptome indicates contribution of WNT signaling pathways in the pathogenesis of Apert syndrome. Turk J Pediatr 2017; 59: 619-624. Cranial sutures are unossified connective tissue structures between the cranial bones, which allow expansion of these bones during development. Premature ossification of these structures is called craniosynostosis. Apert syndrome is a well-defined genetic syndrome, which is characterized by craniosynostosis and arises as a result of two missense mutations in Fibroblast Growth Factor Receptor, type 2 gene (FGFR2). In this study, differentially expressed genes in dermal fibroblasts from individuals with Apert syndrome and controls were investigated to identify important pathways in the pathogenesis of Apert syndrome. For this purpose, primary skin fibroblast cultures obtained from 3 individuals with Apert syndrome and 3 controls without craniosynostosis were compared by transcriptome microarray, GeneChip Human Genome U133 Plus 2.0. As a result, 181 genes were shown to be differentially expressed between experimental groups. Among these, 10 genes, which significantly differ in Apert syndrome fibroblasts compared to controls, were shown to be involved in a common interaction network and have common Gene ontology (GO) biological processes terms. COL11A1, COMP, CPXM2, ITGA8, MGF and TNC are differentially expressed genes that have GO terms associated with extracellular matrix (ECM) organization, while FRZB, SFRP2 and WNT2 are involved in WNT signaling pathway. Reorganization of ECM and changes in WNT signaling pathway show that Apert syndrome primary fibroblast cultures may have an increased potential for bone differentiation. The results of this study support craniosynostosis in Apert syndrome may be the result of fast and early differentiation of connective tissue along the sutures.

An Adult Patient with Monosomy 18p, Growth Hormone Deficiency and Selective IgA Deficiency

Monosomy 18p is a relatively frequent deletion syndrome with an estimated frequency of one in 50,000 liveborns. Most frequent findings consist of mild to moderate growth deficiency, intellectual disability, microcephaly, and facial dysmorphic features including ptosis, epicanthic folds, low nasal bridge, hypertelorism and large protruding ears. Anomalies of other systems may accompany. A 31-year-old male patient with dysmorphic facial features, congenital hypothyroidism, growth hormone deficiency and intellectual disability was diagnosed with monosomy 18p. The patient who also suffered from recurrent aphthous stomatitis and otitis during childhood and selective IgA deficiency was also diagnosed. Monosomy 18p in this patient was further analyzed with SNP microarrays. The 18p deletion caused monosomy of a segment larger than 18 Mb, which consisted many OMIM genes. Deleted genes in this region are known to have a diverse array of functions in various cellular processes. Estimating the possible pathogenic roles of these gene deletions over cellular functions may be difficult for today, however, precise delineation of molecular findings would lead to a better understanding of disease pathogenesis in future.

OR2-001 – The possible role of pyrin on cell migration

MEFV which encodes pyrin, cause familial Mediterranean fever (FMF), the most common auto-inflammatory disease. The pyrin protein appears to be a regulator of inflammation, but its exact role on inflammatory pathways is still controversial. Several pyrin-interacting proteins have been identified, each of which are related to inflammation through regulation of cell death, cytokine secretion, and cytoskeletal signaling. It has been documented that in migrating human monocytes, pyrin protein is dramatically polarized at the leading edge, where it co-localizes with polymerizing actin. Thus, we hypothesized that pyrin may have a key role in cell migration through its interaction with well-known regulators of inflammatory cell migration.

PW01-001 – Pyrin-PSTPIP1 relation during cell migration

MEFV (MEditerranien FeVer) gene mutations cause Familial Mediterranean Fever (FMF). This gene encodes a protein termed as Pyrin, which appears to play an important role in the inflammatory pathways. It is far characterized that Pyrin, which is expressed in neutrophils, interacts with PSTPIP1 and actin proteins. In previous studies PSTPIP1 has been shown to interact with cell migration proteins and actin polymerization is a main force driving neutrophil migration. Therefore, we hypothesized that Pyrin can play role in cell migration through the interaction with actin and PSTPIP1.