Ibrahim Keser

Molecular analysis of beta-thalassemia and sickle cell anemia in Antalya.

We have studied 918 chromosomes for mutations leading to β-thalassemia and sickle cell anemia, which are the two most frequently found monogenic disorders in Antalya, Turkey. Three hundred and seventy-seven postnatal and 82 prenatal cases were studied between 2000 and May 2003 in our center using reverse dot blot hybridization (RDBH) with 22 probes specific for Mediterranean populations. In this study, IVSI-110 (G→A) appeared to be the most common mutation with an occurrence rate of 44.4% among the 16 different mutations found to be associated with β-thalassemia. Heterozygosity for IVSI-110 was the most prevalent combination, whereas 34 of our 377 postnatal cases showed homozygosity for this mutation, a genotype leading to β-thalassemia major. The total percentage of postnatal patients clinically diagnosed as β-thalassemia major was 18.6%, whereas 5% of the cases were diagnosed clinically as β-thalassemia intermedia. One new Hb variant, Hb Antalya, and one new mutation, Cod 3 (+T) were found. HbS accounted for 10.3% of all mutations; homozygosity was found in 1.9% of all cases. Of the 82 cases analysed prenatally for β-globin gene mutations and by cytogenetic techniques for possible chromosomal abnormalities, 21 fetuses were found to be affected with β-globin gene mutations. One of these fetuses was also found to have a 45,X karyotype, and 1 had a 46,XY/47,XY,+22 karyotype. Quite a high rate of consanguineous marriages in Antalya (35.17%) renders mutation screening, genetic counseling, and educational programs held by our Thalassemia Unit essential. This study was the first to be performed specifically in our region where hemoglobinopathies are most frequent as a consequence of migrations of racially and culturally distinct groups to the area in the distant past.

Germline hMSH2 and hMLH1 gene mutations in incomplete HNPCC families.

Hereditary non‐polyposis colon cancer (HNPCC) is a common hereditary disease characterized by a predisposition to an early onset of colorectal cancer. The majority of the HNPCC families carry germline mutations of either hMSH2 or hMLH1 genes, whereas germline mutations of hPMS1 and hPMS2 genes have rarely been observed. Almost all of the germline mutations reported so far concern typical HNPCC families. However, there are families that display aggregations of colon cancer even though they do not fulfil all HNPCC criteria (incomplete HNPCC families) as well as sporadic cases of early onset colon cancers that could be related to germline mutations of these genes. Therefore, we screened germline mutations of hMSH2 and hMLH1 genes in 3 groups of patients from France and Turkey: typical HNPCC (n = 3), incomplete HNPCC (n = 9) and young patients without apparent familial history (n = 7). By in vitro synthesis of protein assay, heteroduplex analysis and direct genomic sequencing, we identified 1 family with hMSH2 mutation and 5 families with hMLH1 mutations. Two of the 3 HNPCC families (66%) displayed hMLH1 germline mutations. Interestingly, 4 of 9 families with incomplete HNPCC (44%) also displayed mutations of hMSH2 or hMLH1 genes. In contrast, no germline mutation of these genes was found in 7 young patients. Our results show that germline mutations of hMSH2 and hMLH1 genes contribute to a significant fraction of familial predisposition to colon cancer cases that do not fulfil all diagnostic criteria of HNPCC. Int. J. Cancer 73:831–836, 1997.

Effects of hormone replacement therapy on bone mineral density in Turkish patients with or without COL1A1 Sp1 binding site polymorphism

Aim:  To evaluate the effects of hormone replacement therapy (HRT) on bone mineral density (BMD) in patients with or without COL1A1 Sp1 binding site polymorphism.

Relationship between SP1 polymorphism and osteoporosis in β-thalassemia major patients

Background: β‐Thalassemia is an autosomal recessive disease characterized by defective β‐globin chain production. Osteoporosis is an important cause of morbidity in patients with β‐thalassemia major. The pathogenesis of reduced bone mineral density (BMD) is multifactorial. A range of genetics factors have been implicated in other populations of patients with osteoporosis. Polymorphism at the Sp1 binding site of the collagen type I A1 (COLIA1) gene is thought to be an important factor in the development of osteoporosis.

The association between intragenic SNP haplotypes and mutations of the beta globin gene in a Turkish population

Identification of the beta globin gene mutation-related haplotypes is of interest for the delineation of the clinical heterogeneity as well as understanding of the origin and spreading of the beta globin gene mutations. We screened the whole beta globin gene in 197 Turkish patients by direct sequencing and performed Haploview analyses for beta globin gene haplotyping using five common intragenic SNPs; rs713040, rs10768683, rs7480526, rs7946748, and rs1609812. We found 25 different beta globin gene point mutations by sequencing. A Turkish type of inv/del mutation by MLPA and Gap-PCR was also detected with additional studies. The seven most common mutations with higher frequency of 5% were IVS-I-110 (G>A) (35.6%), Hb S(10.6%), IVS-I-6 (T>C) (7.4%), IVS-I-1 (G>A) (6.9%), IVS-II-1 (G>A) (6.9%), Cod8(-AA) (6%), IVS-II-745 (C>G) (5.1%) and accounted for 78.7% of all mutations. We identified seven different haplotypes (Haplotype I-VII) using five intragenic single nucleotide polymorphisms (SNPs) genotyped by sequencing of the beta globin gene. The association between the mutations and the haplotypes was defined for 16 different mutations. We suggest that haplotyping by these five intragenic SNPs will provide useful information about the origin of the mutations and gene flow among as well as the explanation of the clinical heterogeneity.

Neutrophil oxidative metabolism in Down syndrome patients with congenital heart defects.

Down syndrome (DS) occurs when an individual has three, rather than two, copies of the 21st chromosome. Cytosolic superoxide dismutase (SOD‐1) is encoded by a gene on chromosome 21 and thus, SOD‐1 activity is elevated in patients with DS. Forty percent of all cases with DS are associated with congenital heart defects (CHD). Although the contribution of SOD1 to disease phenotype is unknown, it is considered to be a “molecular marker” of the disease. It was hypothesized herein that the presence of CHD may alter the expression of SOD1 and oxidative metabolism in patients with DS. This hypothesis was tested via four experimental groups as follows: patients with DS without CHD, DS patients with CHD, CHD patients without DS and controls. Expression and activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), myeloperoxidase (MPO), and catalase (CAT) were determined in neutrophils from all experimental groups. Intracellular hydrogen peroxide concentration and superoxide release were also evaluated in neutrophils. A significant increase was observed in SOD and GPx amount and activity in patients with DS with and without CHD. No significant difference was found in the amount and activity of MPO and CAT among the different experimental groups. Intracellular hydrogen peroxide concentration was similar in all groups, whereas a prominent decrease was seen in superoxide release in cases with DS. Patients with DS with and without CHD showed no significant differences in any of the measured parameters. The data suggest that CHD observed in patients with DS does not result from altered redox metabolism associated with the disease. Environ. Mol. Mutagen., 2010.

MOLECULAR ANALYSIS OF FRAGILE X SYNDROME IN ANTALYA PROVINCE

BACKGROUND Detection of the (CGG)n repeats in the FMR1 gene that cause the fragile X syndrome (FXS), has become a milestone for phenotype-genotype correlation in FXS. AIMS To screen the FMR1 gene CGG repeats in index cases with FXS and their family members in the Antalya Province. SETTING AND DESIGN This study was prospectively conducted between January 2000 and March 2005 in Department of Medical Biology and Genetics, Faculty of Medicine, Akdeniz University, Antalya. MATERIALS AND METHODS A series of 132 cases from three hospitals in Antalya Province were studied. All cases were molecularly screened using non-radioactive Expand Long PCR method that was confirmed by Southern blotting. RESULTS Seventeen out of 132 cases were found to have a full mutation, including three that were mosaic for premutations/full mutations. Of the 132 cases, eight were found to have the premutation size of the CGG repeats. The remaining 107 cases were identified as normal. CONCLUSIONS Due to premature ovarian failure and Fragile X premutation Tremor/Ataxia Syndrome related with the premutation, the detection of the premutation will provide valuable information both for clinical follow-up and genetic counseling. In conclusion, our data suggest that expansion of CGG repeats in the FMR1 gene can be analyzed by Expand Long PCR, an efficient and non-radioactive method that can be used to monitor the expansion of premutation to full mutation, which would eventually lead to reduce the FXS prevalence.

Prenatal diagnosis of β-thalassemia and other hemoglobinopathies in southwestern Turkey.

Our aim was to evaluate the prenatal diagnosis of β-thalassemia (β-thal) and other hemoglobinopathies in a region with high frequency. After detection by premarital or antenatal screening, 312 patients underwent 420 prenatal diagnostic procedures for 407 fetuses in a 10-year period. Fetal samples were collected by chorionic villi sampling (CVS) in the first trimester and amniocentesis and cordocentesis in the second trimester. Mutation analyses of β-globin and cytogenetic analyses were performed and the most common mutations detected were: IVS-I-110 (G>A), IVS-II-1 (G>A), IVS-I-6 (T>C) and IVS-II-745 (C>G). Hb S [β6(A3)Glu→Val, GAG>GTG)] was the most common hemoglobin (Hb) variant with a frequency of 6.3%. Among 407 fetuses, 105 (25.8%) were diagnosed as affected, while 201 (49.4%) were carriers and 101 (24.8%) were normal. Cytogenetic analyses revealed nine fetuses (2.3%) with numerical chromosomal abnormalities as regular or mosaicism. Prenatal diagnosis of common hemoglobinopathies is safe and effective. Performing cytogenetic analysis in excess fetal material is an acceptable option.

Frequencies of four genetic polymorphisms in the CYP1A2 gene in Turkish population

Cytochrome P450 (CYP) 1A2 gene is involved in the metabolic activation of several carcinogens and altered metabolization of some clinically used drugs. We aimed to investigate the distributions of genetic polymorphisms-3860 (G/A)(CYP1A2*1C) and-2467 (T/del)(CYP1A2*1D) in the 5′-flanking region and-739 (T/G)(CYP1A2*1E) and-163(C/A)(CYP1A2*1F) in the first intron of the CYP1A2 gene in 110 unrelated healthy Turkish volunteers by PCR-RFLP technique. The frequencies of each polymorphism in Turkish population were found as 0.04, 0.92, 0.01, 0.27 for CYP1A2*1C, CYP1A2*1D, CYP1A2*1E, CYP1A2*1F, respectively. Compared with other populations, CYP1A2*1Dhas been found to be significantly increased in Turkish population. On the other hand, in general, the frequencies of the other polymorphisms were concordant with those in the Egyptian and Caucasian populations, and were different from those in the Japanese, Chinese and Ethiopian populations. Our results suggest that due to increased frequency of CYP1A2*1D in Turkish population, unctional significance of CYP1A2*1D should be evaluated. It might be screened to determine the relationship between CYP1A2*1D and CYP1A2 related drug metabolisms in associated groups.

Pure and complete 12p trisomy due to a maternal centric fission of chromosome 12

Pure and complete 12p trisomy are rare. Here, we report on a unique patient with trisomy 12p syndrome due to centric fission of maternal chromosome 12. Conventional cytogenetic and fluorescence in situ hybridization (FISH) techniques revealed the propositas karyotype to be 47,XX,+fis(12)(p10)mat whereas the maternal one was 47,XX,‐12,+fis(12)(p10),+fis(12) (q10). This is the first report on centric fission of chromosome 12 leading to stable telocentrics, each with a fully functional centromere. Our observation shows that the centric fission of chromosome 12 can be a new mechanism for generation of a partial centromere and trisomy 12p syndrome.