Browsing by Author "Ozcelik, T."

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Open Access
Analysis of skewed X-chromosome inactivation in females with rheumatoid arthritis and autoimmune thyroid diseases
(BioMed Central, 2009) Chabchoub, G.; Uz, E.; Maalej, A.; Mustafa, C. A.; Rebai, A.; Mnif, M.; Bahloul, Z.; Farid, N. R.; Ozcelik, T.; Ayadi, H.
Introduction The majority of autoimmune diseases such as rheumatoid arthritis (RA) and autoimmune thyroid diseases (AITDs) are characterized by a striking female predominance superimposed on a predisposing genetic background. The role of extremely skewed X-chromosome inactivation (XCI) has been questioned in the pathogenesis of several autoimmune diseases.
Open Access
Characterization of a novel zebrafish (Danio rerio) gene, wdr81, associated with cerebellar ataxia, mental retardation and dysequilibrium syndrome (CAMRQ)
(BioMed Central Ltd., 2015) Doldur-Balli, F.; Ozel, M. N.; Gulsuner, S.; Tekinay, A. B.; Ozcelik, T.; Konu, O.; Adams, M. M.
Background: WDR81 (WD repeat-containing protein 81) is associated with cerebellar ataxia, mental retardation and disequilibrium syndrome (CAMRQ2, [MIM 610185]). Human and mouse studies suggest that it might be a gene of importance during neurodevelopment. This study aimed at fully characterizing the structure of the wdr81 transcript, detecting the possible transcript variants and revealing its expression profile in zebrafish, a powerful model organism for studying development and disease. Results: As expected in human and mouse orthologous proteins, zebrafish wdr81 is predicted to possess a BEACH (Beige and Chediak-Higashi) domain, a major facilitator superfamily domain and WD40-repeats, which indicates a conserved function in these species. We observed that zebrafish wdr81 encodes one open reading frame while the transcript has one 5' untranslated region (UTR) and the prediction of the 3' UTR was mainly confirmed along with a detected insertion site in the embryo and adult brain. This insertion site was also found in testis, heart, liver, eye, tail and muscle, however, there was no amplicon in kidney, intestine and gills, which might be the result of possible alternative polyadenylation processes among tissues. The 5 and 18 hpf were critical timepoints of development regarding wdr81 expression. Furthermore, the signal of the RNA probe was stronger in the eye and brain at 18 and 48 hpf, then decreased at 72 hpf. Finally, expression of wdr81 was detected in the adult brain and eye tissues, including but not restricted to photoreceptors of the retina, presumptive Purkinje cells and some neurogenic brains regions. Conclusions: Taken together these data emphasize the importance of this gene during neurodevelopment and a possible role for neuronal proliferation. Our data provide a basis for further studies to fully understand the function of wdr81.
Open Access
Concomitant inactivation of p53 and Chk2 in breast cancer
(Nature Publishing Group, 2002) Sullivan, A.; Yuille, M.; Repellin, C.; Reddy, A.; Reelfs, O.; Bell, A.; Dunne, B.; Gusterson, B. A.; Osin, P.; Farrell, P. J.; Yulug, I.; Evans, A.; Ozcelik, T.; Gasco, M.; Crook, T.
Open Access
Disruption of HDX gene in premature ovarian failure
(Taylor & Francis, 2013) Okten, G.; Gunes, S.; Onat, O. E.; Tukun, A.; Ozcelik, T.; Kocak, I.
We present a case of a 19-year-old phenotypically normal girl with premature ovarian failure. Cytogenetic analysis using G banding and fluorescence in situ hybridization (FISH) from cultured peripheral blood lymphocytes of the patient and the family revealed a de novo X;15 translocation and the imbalance to be 46,X,t(X;15)(Xpter → Xq21::15q11 → 15qter;15pter → 15q11::Xq21 → Xqter). ish (CEPX+, wep15+, ISNRPN+, PML+, D15S10+, wcp15-, SNRRN-, PML-)[20]. The X chromosome inactivation (XCI) assay revealed a completely skewed XCI pattern in which selective pressure favors an active maternal allele. The Affymetrix 2.7 M cytogenetics whole-Genome array confirmed the chromosomal imbalance and identified disruption of the HDX gene at Xq21, the translocation breakpoint. © 2013 Informa Healthcare USA, Inc.
Open Access
Evaluation of X chromosome inactivation with respect to HLA genetic susceptibility in rheumatoid arthritis and systemic sclerosis
(Public Library of Science, 2016) Kanaan, S. B.; Onat, O. E.; Balandraud, N.; Martin, G. V.; Nelson, J. L.; Azzouz, D. F.; Auger, I.; Arnoux, F.; Martin, M.; Roudier, J.; Ozcelik, T.; Lambert, N. C.
Background: Autoimmune diseases, including rheumatoid arthritis (RA) and systemic sclerosis (SSc) are characterized by a strong genetic susceptibility from the Human Leucocyte Antigen (HLA) locus. Additionally, disorders of epigenetic processes, in particular non-random X chromosome inactivation (XCI), have been reported in many female-predominant autoimmune diseases. Here we test the hypothesis that women with RA or SSc who are strongly genetically predisposed are less susceptible to XCI bias. Methods: Using methylation sensitive genotyping of the androgen receptor (AR) gene, XCI profiles were performed in peripheral blood mononuclear cells from 161 women with RA, 96 women with SSc and 100 healthy women. HLA-DRB1 and DQB1 were genotyped. Presence of specific autoantibodies was documented for patients. XCI skewing was defined as having a ratio ≥ 80:20 of cells inactivating the same X chromosome. Results: 110 women with RA, 68 women with SSc, and 69 controls were informative for the AR polymorphism. Among them 40.9% of RA patients and 36.8% of SSc patients had skewed XCI compared to 17.4% of healthy women (P = 0.002 and 0.018, respectively). Presence of RA-susceptibility alleles coding for the "shared epitope" correlated with higher skewing among RA patients (P = 0.002) and such correlation was not observed in other women, healthy or with SSc. Presence of SSc-susceptibility alleles did not correlate with XCI patterns among SSc patients. Conclusion: Data demonstrate XCI skewing in both RA and SSc compared to healthy women. Unexpectedly, skewed XCI occurs more often in women with RA carrying the shared epitope, which usually reflects severe disease. This reinforces the view that loss of mosaicism in peripheral blood may be a consequence of chronic autoimmunity. © 2016 Kanaan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Open Access
Evidence from autoimmune thyroiditis of skewed X-chromosome inactivation in female predisposition to autoimmunity
(Nature Publishing Group, 2006) Ozcelik, T.; Uz, E.; Akyerli, C. B.; Bagislar, S.; Mustafa, C. A.; Gursoy, A.; Akarsu, N.; Toruner, G.; Kamel, N.; Gullu, S.
The etiologic factors in the development of autoimmune thyroid diseases (AITDs) are not fully understood. We investigated the role of skewed X-chromosome inactivation (XCI) mosaicism in female predisposition to AITDs. One hundred and ten female AITDs patients (81 Hashimoto's thyroiditis (HT), 29 Graves' disease (GD)), and 160 female controls were analyzed for the androgen receptor locus by the HpaII/polymerase chain reaction assay to assess XCI patterns in DNA extracted from peripheral blood cells. In addition, thyroid biopsy, buccal mucosa, and hair follicle specimens were obtained from five patients whose blood revealed an extremely skewed pattern of XCI, and the analysis was repeated. Skewed XCI was observed in DNA from peripheral blood cells in 28 of 83 informative patients (34%) as compared with 10 of 124 informative controls (8% P<0.0001). Extreme skewing was present in 16 patients (19%), but only in three controls (2.4% P<60;0.0001). The buccal mucosa, and although less marked, the thyroid specimens also showed skewing. Analysis of two familial cases showed that only the affected individuals demonstrate skewed XCI patterns. Based on these results, skewed XCI mosaicism may play a significant role in the pathogenesis of AITDs.
Open Access
Extramedullary relapse following allogeneic stem cell transplantation in acute promyelocytic leukemia: the role of ATRA
(Fondazione Ferrata Storti, 2001) Ustun, C.; Arat, M.; Celebi, H.; Akan, H.; Ilhan, O.; Ozcelik, T.; Burgess, R. E.; Koc, H.
Open Access
Extreme clonality in lymphoblastoid cell lines with implications for allele specific expression analyses
(2008) Plagnol V.; Uz, E.; Wallace, C.; Stevens H.; Clayton, D.; Ozcelik, T.; Todd J.A.
Lymphoblastoid cell lines (LCL) are being actively and extensively used to examine the expression of specific genes and (genome-wide expression profiles, including allele specific expression assays. However, it has recently been shown that approximately 10% of human genes exhibit random patterns of monoallelic expression within single clones of LCLs. Consequently allelic imbalance studies could be significantly compromised if bulk populations of donor cells are clonal, or near clonal. Here, using X chromosome inactivation as a readout, we confirm and quantify widespread near monoclonality in two independent sets of cell lines. Consequently, we recommend where possible the use of bulk, non cell line, ex vivo cells for allele specific expression assays. © 2008 Plagnol et al.
Open Access
Extremely skewed X-chromosome inactivation is increased in pre-eclampsia
(Springer-Verlag, 2007-03) Uz, E.; Dolen, I.; Al, A. R.; Ozcelik, T.
Pre-eclampsia is a disorder that affects approximately 5% of pregnancies. We tested the hypothesis that skewed X-chromosome inactivation (XCI) could be involved in the pathogenesis of pre-eclampsia. Peripheral blood DNA was obtained from 67 pre-eclampsia patients and 130 control women. Androgen receptor (AR) was analyzed by the Hpa II/polymerase chain reaction assay to assess XCI patterns in DNA extracted from peripheral-blood cells. In addition, buccal cells were obtained from seven patients, and the analysis repeated. Extremely skewed XCI was observed in 10 of 46 informative patients (21.74%), and in 2 of 86 informative controls (2.33%, P = 0.0005; χ2 test). Our findings support a role for the X-chromosome in the pathogenesis of pre-eclampsia in a subgroup of patients.
Open Access
Extremely skewed X-chromosome inactivation patterns in women with recurrent spontaneous abortion
(Wiley-Blackwell Publishing Asia, 2006) Bagislar, S.; Ustuner, I.; Cengiz, B.; Soylemez, F.; Akyerli, C. B.; Ceylaner, S.; Ceylaner, G.; Acar, A.; Ozcelik, T.
Background: The role of extremely skewed X-chromosome inactivation (XCI) has been questioned in the pathogenesis of recurrent spontaneous abortion (RSA) but the results obtained were conflicting. Aims: We therefore investigated the XCI patterns in peripheral blood DNA obtained from 80 patients who had RSA and 160 age-matched controls. Methods: Pregnancy history, age, karyotype, and disease information was collected from all subjects. The methylation status of a highly polymorphic cytosine-adenine-guanine repeat in the androgen-receptor (AR) gene was determined by use of methylation-sensitive restriction enzyme HpaII and polymerase chain reaction. Results: Skewed XCI (> 8 5% skewing) was observed in 13 of the 62 patients informative for the AR polymorphism (20.9%), and eight of the 124 informative controls (6.4%) (P = 0.0069; χ 2 test). More importantly, extremely skewed XCI, defined as > 90% inactivation of one allele, was present in 11 (17.7%) patients, and in only two controls (P = 0.0002; χ 2 test). Conclusions: These results support the interpretation that disturbances in XCI mosaicism may be involved in the pathogenesis of RSA.
Open Access
Frequent demonstration of human herpesvirus 8 (HHV-8) in bone marrow biopsy samples from Turkish patients with multiple myeloma (MM)
(Nature Publishing, 2001) Beksac, M.; Ma, M.; Akyerli, C.; DerDanielian, M.; Zhang, L.; Liu, J.; Arat, M.; Konuk, N.; Koc, H.; Ozcelik, T.; Vescio, R.; Berenson, J. R.
In order to investigate the frequency of HHV-8 in MM patients from another geographic location, we obtained fresh bone marrow (BM) biopsies from Turkish patients with MM (n = 21), monoclonal gammopathy of undetermined significance (MGUS) (n = 2), plasmacytoma (n = 1) with BM plasma cell infiltration, various hematological disorders (n = 6), and five healthy Turkish controls. The frequency of HHV-8 was analyzed by polymerase chain reaction (PCR) in two independent laboratories in the USA and in Turkey. Using fresh BM biopsies, 17/21 MM patients were positive for HHV-8 whereas all five healthy controls, and six patients with other hematological disorders were negative. Two patients with MGUS, and one patient with a solitary plasmacytoma were also negative. The data from the two laboratories were completely concordant. Also using primer pairs for v IRF and v IL-8R confirmed the results observed with the KS330233 primers. Furthermore, sequence analysis demonstrated a C3 strain pattern in the ORF26 region which was also found in MM patients from the US. Thus, HHV-8 is present in the majority of Turkish MM patients, and the absence of the virus in healthy controls further supports its role in the pathogenesis of MM.
Open Access
Genetic education and the challenge of genomic medicine development of core competences to support preparation of health professionals in Europe
(Nature Publishing Group, 2010) Skirton, H.; Lewis, C.; Kent, A.; Domenico, A. C.; Bloch-Zupan, A.; Cornel, M.; DeLozier, C.; Farndon, P.; Goetz, P.; Hongson, S.; Houge, G.; Hulten, M.; Kosztolanyi, G.; Kucinskas, V.; Ozcelik, T.; Serqueiros, J.; Soller, M.; Tranebjaerg, L.
The use of genetics and genomics within a wide range of health-care settings requires health professionals to develop expertise to practise appropriately. There is a need for a common minimum standard of competence in genetics for health professionals in Europe but because of differences in professional education and regulation between European countries, setting curricula may not be practical. Core competences are used as a basis for health professional education in many fields and settings. An Expert Group working under the auspices of the EuroGentest project and European Society of Human Genetics Education Committee agreed that a pragmatic solution to the need to establish common standards for education and practice in genetic health care was to agree to a set of core competences that could apply across Europe. These were agreed through an exhaustive process of consultation with relevant health professionals and patient groups. Sets of competences for practitioners working in primary, secondary and tertiary care have been agreed and were approved by the European Society of Human Genetics. The competences provide an appropriate framework for genetics education of health professionals across national boundaries, and the suggested learning outcomes are available to guide development of curricula that are appropriate to the national context, educational system and health-care setting of the professional involved. Collaboration between individuals from many European countries and professions has resulted in an adaptable framework for both pre-registration and continuing professional education. This competence framework has the potential to improve the quality of genetic health care for patients globally.
Open Access
Increased frequency of extremely skewed X chromosome inactivation in juvenile idiopathic arthritis
(John Wiley & Sons, Inc., 2009) Uz, E.; Mustafa, C.; Topaloglu, R.; Bilginer, Y.; Dursun, A.; Kasapcopur, O.; Ozen, S.; Bakkaloglu, A.; Ozcelik, T.
Objective. Juvenile idiopathic arthritis (JIA) is a childhood rheumatic disease of unknown etiology. Two subgroups of JIA, i.e., oligoarticular and polyarticular, are thought to have an autoimmune component, and show a higher female:male ratio. Skewed X chromosome inactivation (XCI) has previously been shown to be associated with scleroderma and autoimmune thyroiditis, 2 autoimmune disorders occurring predominantly in females. This study was undertaken to extend the analysis to the pediatric age group and to determine the XCI profiles of patients with JIA.
Open Access
Missense mutation in the ATPase, aminophospholipid transporter protein ATP8A2 is associated with cerebellar atrophy and quadrupedal locomotion
(Nature Publishing Group, 2013) Onat, O. E.; Gulsuner, S.; Bilguvar, K.; Basak, A. N.; Topaloglu, H.; Tan, M.; Tan, U.; Gunel, M.; Ozcelik, T.
Cerebellar ataxia, mental retardation and dysequilibrium syndrome is a rare and heterogeneous condition. We investigated a consanguineous family from Turkey with four affected individuals exhibiting the condition. Homozygosity mapping revealed that several shared homozygous regions, including chromosome 13q12. Targeted next-generation sequencing of an affected individual followed by segregation analysis, population screening and prediction approaches revealed a novel missense variant, p.I376M, in ATP8A2. The mutation lies in a highly conserved C-terminal transmembrane region of E1 E2 ATPase domain. The ATP8A2 gene is mainly expressed in brain and development, in particular cerebellum. Interestingly, an unrelated individual has been identified, in whom mental retardation and severe hypotonia is associated with a de novo t(10;13) balanced translocation resulting with the disruption of ATP8A2. These findings suggest that ATP8A2 is involved in the development of the cerebro-cerebellar structures required for posture and gait in humans. © 2013 Macmillan Publishers Limited All rights reserved.
Open Access
Mutations in RAD21 disrupt regulation of apob in patients with chronic intestinal pseudo-obstruction
(W.B. Saunders, 2015) Bonora, E.; Bianco, F.; Cordeddu, L.; Bamshad, M.; Francescatto, L.; Dowless, D.; Stanghellini, V.; Cogliandro, R. F.; Lindberg, G.; Mungan, Z.; Cefle, K.; Ozcelik, T.; Palanduz, S.; Ozturk, S.; Gedikbasi, A.; Gori, A.; Pippucci, T.; Graziano, C.; Volta, U.; Caio, G.; Barbara, G.; D'Amato, M.; Seri, M.; Katsanis, N.; Romeo, G.; De Giorgio, R.
Background Aims Chronic intestinal pseudo-obstruction (CIPO) is characterized by severe intestinal dysmotility that mimics a mechanical subocclusion with no evidence of gut obstruction. We searched for genetic variants associated with CIPO to increase our understanding of its pathogenesis and to identify potential biomarkers. Methods We performed whole-exome sequencing of genomic DNA from patients with familial CIPO syndrome. Blood and lymphoblastoid cells were collected from patients and controls (individuals without CIPO); levels of messenger RNA (mRNA) and proteins were analyzed by quantitative reverse-transcription polymerase chain reaction, immunoblot, and mobility shift assays. Complementary DNAs were transfected into HEK293 cells. Expression of rad21 was suppressed in zebrafish embryos using a splice-blocking morpholino (rad21a). Gut tissues were collected and analyzed. Results We identified a homozygous mutation (p.622, encodes Ala>Thr) in RAD21 in patients from a consanguineous family with CIPO. Expression of RUNX1, a target of RAD21, was reduced in cells from patients with CIPO compared with controls. In zebrafish, suppression of rad21a reduced expression of runx1; this phenotype was corrected by injection of human RAD21 mRNA, but not with the mRNA from the mutated p.622 allele. rad21a Morpholino zebrafish had delayed intestinal transit and greatly reduced numbers of enteric neurons, similar to patients with CIPO. This defect was greater in zebrafish with suppressed expression of ret and rad21, indicating their interaction in the regulation of gut neurogenesis. The promoter region of APOB bound RAD21 but not RAD21 p.622 Ala>Thr; expression of wild-type RAD21 in HEK293 cells repressed expression of APOB, compared with control vector. The gut-specific isoform of APOB (APOB48) is overexpressed in sera from patients with CIPO who carry the RAD21 mutation. APOB48 also is overexpressed in sporadic CIPO in sera and gut biopsy specimens. Conclusions Some patients with CIPO carry mutations in RAD21 that disrupt the ability of its product to regulate genes such as RUNX1 and APOB. Reduced expression of rad21 in zebrafish, and dysregulation of these target genes, disrupts intestinal transit and the development of enteric neurons.
Open Access
Mutations in the very low-density lipoprotein receptor VLDLR cause cerebellar hypoplasia and quadrupedal locomotion in humans
(National Academy of Sciences, 2008) Ozcelik, T.; Akarsu, N.; Uz, E.; Caglayan, S.; Gulsuner, S.; Onat, O. E.; Tan, M.; Tan, U.
Quadrupedal gait in humans, also known as Unertan syndrome, is a rare phenotype associated with dysarthric speech, mental retardation, and varying degrees of cerebrocerebellar hypoplasia. Four large consanguineous kindreds from Turkey manifest this phenotype. In two families (A and D), shared homozygosity among affected relatives mapped the trait to a 1.3-Mb region of chromosome 9p24. This genomic region includes the VLDLR gene, which encodes the very low-density lipoprotein receptor, a component of the reelin signaling pathway involved in neuroblast migration in the cerebral cortex and cerebellum. Sequence analysis of VLDLR revealed nonsense mutation R257X in family A and single-nucleotide deletion c2339delT in family D. Both these mutations are predicted to lead to truncated proteins lacking transmembrane and signaling domains. In two other families (B and C), the phenotype is not linked to chromosome 9p. Our data indicate that mutations in VLDLR impair cerebrocerebellar function, conferring in these families a dramatic influence on gait, and that hereditary disorders associated with quadrupedal gait in humans are genetically heterogeneous.
Open Access
Neuro-ophthalmologic findings in humans with quadrupedal locomotion
(2012) Sarac O.; Gulsuner, S.; Yildiz-Tasci, Y.; Ozcelik, T.; Kansu, T.
Purpose: To report the neuro-ophthalmologic findings in four patients from the same family with cerebellar ataxia, mental retardation, and dysequilibrium syndrome (CAMRQ)2 associated with quadrupedal locomotion. Method: A case series. Results: All four patients carry the private missense mutation, WDR81 p.P856L. The brain Magnetic Resonance Imaging (MRI) of these patients revealed morphological abnormalities including mild hypoplasia of the corpus callosum, and atrophy of superior, middle, and inferior peduncles of the cerebellum. All patients had down-beat nystagmus, while two male patients additionally had bilateral temporal disc pallor along with ring-shaped macular atrophy. Conclusions: The neuro-ophthalmic examination in CAMRQ2 revealed downbeat nystagmus in all patients, and temporal disc pallor and macular atrophy in two patients. It remains to be determined whether these findings are consistent in other forms of CAMRQ with mutations in VLDLR or CA8. © 2012 Informa Healthcare USA, Inc.
Open Access
Novel VLDLR microdeletion identified in two Turkish siblings with pachygyria and pontocerebellar atrophy
(Springer, 2010) Kolb, L. E.; Arlier, Z.; Yalcinkaya, C.; Ozturk, A. K.; Moliterno, J. A.; Erturk, O.; Bayrakli, F.; Korkmaz, B.; DiLuna, M. L.; Yasuno, K.; Bilguvar, K.; Ozcelik, T.; Tuysuz, B.; State, M. W.; Gunel, M.
Congenital ataxia with cerebellar hypoplasia is a heterogeneous group of disorders that presents with motor disability, hypotonia, incoordination, and impaired motor development. Among these, disequilibrium syndrome describes a constellation of findings including non-progressive cerebellar ataxia, mental retardation, and cerebellar hypoplasia following an autosomal recessive pattern of inheritance and can be caused by mutations in the Very Low Density Lipoprotein Receptor (VLDLR). Interestingly, while the majority of patients with VLDL-associated cerebellar hypoplasia in the literature use bipedal gait, the previously reported patients of Turkish decent have demonstrated similar neurological sequelae, but rely on quadrupedal gait. We present a consanguinous Turkish family with two siblings with cerebellar atrophy, predominantly frontal pachygyria and ataxic bipedal gait, who were found to have a novel homozygous deletion in the VLDLR gene identified by using high-density single nucleotide polymorphism microarrays for homozygosity mapping and identification of CNVs within these regions. Discovery of disease causing homozygous deletions in the present Turkish family capable of maintaining bipedal movement exemplifies the phenotypic heterogeneity of VLDLR-associated cerebellar hypoplasia and ataxia.
Open Access
Population distribution and ancestry of the cancer protective MDM2 SNP285 (rs117039649)
(Impact Journals LLC, 2014) Knappskog, S.; Gansmo, L. B.; Dibirova, K.; Metspalu, A.; Cybulski, C.; Peterlongo, P.; Aaltonen, L.; Vatten, L.; Romundstad, P.; Hveem, K.; Devilee, P.; Evans, G. D.; Lin, D.; Camp, G. V.; Manolopoulos, V. G.; Osorio, A.; Milani, L.; Ozcelik, T.; Zalloua, P.; Mouzaya, F.; Bliznetz, E.; Balanovska, E.; Pocheshkova, E.; Kucinskas, V.; Atramentova, L.; Nymadawa, P.; Titov, K.; Lavryashina, M.; Yusupov, Y.; Bogdanova, N.; Koshel, S.; Zamora, J.; Wedge, D. C.; Charlesworth, D.; Dörk, T.; Balanovsky, O.; Lønning, P. E.
The MDM2 promoter SNP285C is located on the SNP309G allele. While SNP309G enhances Sp1 transcription factor binding and MDM2 transcription, SNP285C antagonizes Sp1 binding and reduces the risk of breast-, ovary- and endometrial cancer. Assessing SNP285 and 309 genotypes across 25 different ethnic populations (>10.000 individuals), the incidence of SNP285C was 6-8% across European populations except for Finns (1.2%) and Saami (0.3%). The incidence decreased towards the Middle-East and Eastern Russia, and SNP285C was absent among Han Chinese, Mongolians and African Americans. Interhaplotype variation analyses estimated SNP285C to have originated about 14,700 years ago (95% CI: 8,300 - 33,300). Both this estimate and the geographical distribution suggest SNP285C to have arisen after the separation between Caucasians and modern day East Asians (17,000 - 40,000 years ago). We observed a strong inverse correlation (r = -0.805; p < 0.001) between the percentage of SNP309G alleles harboring SNP285C and the MAF for SNP309G itself across different populations suggesting selection and environmental adaptation with respect to MDM2 expression in recent human evolution. In conclusion, we found SNP285C to be a pan-Caucasian variant. Ethnic variation regarding distribution of SNP285C needs to be taken into account when assessing the impact of MDM2 SNPs on cancer risk.
Open Access
Reply to herz et al. and humprey et al.: genetic heterogeneity of cerebellar hypoplasia with quadruprdal locomotion
(National Academy of Sciences, 2008) Ozcelik, T.; Akarsu, N.; Uz, E.; Caglayan, S.; Gulsuner, S.; Onat, O. E.; Tan, M.; Tan, U.