Emmanuel Kanavakis

Characterization of a novel 21-kb deletion, CFTRdele2,3(21 kb), in the CFTR gene: a cystic fibrosis mutation of Slavic origin common in Central and East Europe.

Abstract. We report a large genomic deletion of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, viz., a deletion that is frequently observed in Central and Eastern Europe. The mutation, termed CFTRdele2,3(21xa0kb), deletes 21,080xa0bp spanning intronsxa01–3 of the CFTR gene. Transcript analyses have revealed that this deletion results in the loss of exonsxa02 and 3 in epithelial CFTR mRNA, thereby producing a premature termination signal within exonxa04. In order to develop a simple polymerase chain reaction assay for this allele, we defined the end-points of the deletion at the DNA sequence level. We next screened for this mutation in a representative set of European and European-derived populations. Some 197 CF patients, including seven homozygotes, bearing this mutation have been identified during the course of our study. Clinical evaluation of CFTRdele2,3(21xa0kb) homozygotes and a comparison of compound heterozygotes for ΔF508/CFTRdele2,3(21xa0kb) with pairwise-matched ΔF508 homozygotes indicate that this deletion represents a severe mutation associated with pancreatic insufficiency and early age at diagnosis. Current data show that the mutation is particularly common in Czech (6.4% of all CF chromosomes), Russian (5.2%), Belorussian (3.3%), Austrian (2.6%), German (1.5%), Polish (1.5%), Slovenian (1.5%), Ukrainian (1.2%), and Slovak patients (1.1%). It has also been found in Lithuania, Latvia, Macedonia and Greece and has sporadically been observed in Canada, USA, France, Spain, Turkey, and UK, but not in CF patients from Bulgaria, Croatia, Romania or Serbia. Haplotype analysis has identified the same extragenic CF-haplotype XV-2c/KM.19 A and the same infrequent intragenic microsatellite haplotype 16–33–13 (IVS8CA-IVS17bTA-IVS17bCA) in all examined CFTRdele2,3(21xa0kb) chromosomes, suggesting a common origin for this deletion. We conclude that the 21-kb deletion is a frequent and severe CF mutation in populations of Eastern- and Western-Slavic descent.

Assessment of oxidative stress in patients with sickle cell disease: The glutathione system and the oxidant-antioxidant status.

Continuous reactive oxygen species (ROS) production in individuals with sickle cell disease (SCD) may alter their overall redox status and cause tissue damage. The aim of this study was to evaluate oxidative stress in patients with SCD using two new assays, FORT (free oxygen radical test) and FORD (free oxygen radical defense) along with assessment of glutathione system including superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) activities, vitamins A, C and E, malondialdehyde (MDA), non-transferrin bound iron (NTBI) and nitric oxide (NO) concentrations. A total of 40 patients with SCD and 25 apparently healthy volunteers (control group) were enrolled in the study. Components of glutathione system, vitamins A, C, and E, and malondialdehyde were determined with reverse-phase HPLC, non-transferrin bound iron (NTBI) was assessed with atomic absorption spectroscopy using graphite furnace, superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GPx) activities were determined spectrophotometrically in red cell lysates, nitric oxide (NO) was detected colorimetrically, while FORT and FORD using colorimetric assays, as two point-of-care tests. The findings revealed significant impairment of the glutathione system indicated by reduced GSH(total) (p<0.00001), GSH(reduced) (p<0.00001) and GSSG (p>0.056) values of SCD patients compared to the control group. ROS expressed as FORT were significantly increased (p<0.00001), while antioxidant defense expressed as FORD was significantly reduced (p<0.02) in SCD group compared to the control group. Age and genotype of the patients as well as therapy of their disease appeared to play no role in their oxidative status.

Multianalyte, dipstick-type, nanoparticle-based DNA biosensor for visual genotyping of single-nucleotide polymorphisms

DNA biosensors involve molecular recognition of the target sequence by hybridization with specific probes and detection by electrochemical, optical or gravimetric transduction. Disposable, dipstick-type biosensors have been developed recently, which enable visual detection of DNA without using instruments. In this context, we report a multianalyte DNA biosensor for visual genotyping of two single-nucleotide polymorphisms (SNPs). As a model, the biosensor was applied to the simultaneous genotyping of two SNPs, entailing the detection of four alleles. A PCR product that flanks both polymorphic sites is subjected to a single primer extension (PEXT) reaction employing four allele-specific primers, each containing a region complementary to an allele and a characteristic segment that enables subsequent capture on a test zone of the biosensor. The primers are extended with dNTPs and biotin-dUTP only if there is perfect complementarity with the interrogated sequence. The PEXT mixture is applied to the biosensor. As the developing buffer migrates along the strip, all the allele-specific primers are captured by immobilized oligonucleotides at the four test zones of the biosensor and detected by antibiotin-functionalized gold nanoparticles. As a result, the test zones are colored red if extension has occurred denoting the presence of the corresponding allele in the original sample. The excess nanoparticles are captured by immobilized biotinylated albumin at the control zone of the sensor forming another red zone that indicates the proper performance of the system. The assay was applied successfully to the genotyping of twenty clinical samples for two common SNPs of MBL2 gene.

Cystic fibrosis patients with the 3272-26A>G splicing mutation have milder disease than F508del homozygotes: a large European study

Editor—Cystic fibrosis (CF, MIM 219700) is a common, severe, autosomal recessive disease caused by mutations in the CF transmembrane conductance regulator ( CFTR ) gene cloned in 1989.1-3The disease, characterised by chronic lung disease which is the main cause of morbidity and mortality, pancreatic dysfunction, raised electrolyte levels in sweat, and male infertility, is caused by altered chloride (Cl−) secretion across the apical membrane of epithelial cells.4 There is, however, substantial variability in the clinical manifestations affecting the various organs.4 5 nnOne single mutation, F508del, generally associated with severe disease, accounts for about 70% of CF chromosomes world wide, although with a heterogeneous geographical distribution.5 Patients homozygous for the F508del mutation have the classical severe form of the disease which includes chronic mucous obstruction of the lung and conducting airways, followed by recurrent infections mostly by Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa), exocrine pancreatic insufficiency (PI), resulting in failure to gain weight and height, and raised levels of Cl−, sodium, and potassium in exocrine sweat.5 However, almost 1000 genetic alterations have been detected in the CFTR gene ( CFTR Mutation Database), most presumed to be disease causing mutations. About half of these are amino acid substitutions (missense mutations) and about 20% are splicing mutations. The remainder are nonsense, frameshift (including small deletions and insertions), and a small proportion of promoter mutations.nnThe relationship between genotype, that is, the mutations in the CFTR gene, and the clinical phenotype of CF patients has been difficult to establish, in particular for lung disease.nnIt was previously shown that the 3272-26A>G mutation leads to the creation of an alternative acceptor splice site competing with the normal one during RNA processing and resulting in the occurrence of an alternatively spliced mRNA with 25 extra nucleotides from …

Cystic fibrosis in Greece: molecular diagnosis, haplotypes, prenatal diagnosis and carrier identification amongst high-risk individuals

Cystic fibrosis (CF) mutation analysis on 437 CF patients, characterized 80 different mutations (20 so far specific to our population) accounting for 91% of CF genes and generating 103 different genotypes. Eight mutations were common [F508del (53.4%), 621+1G>T (5.7%), G542X (3.9%), N1303K (2.6%), 2789+5G>A (1.7%), 2183AA>G (1.4%), E822X (1.4%), R1158X (1%)], 12 showed frequencies between 0.5% and 1%, while the remaining (60) were very rare (1 to 3 alleles). Denaturing gradient gel electrophoresis (DGGE) screening of 12 exons (3, 4, 7, 10, 11, 13, 14b, 16, 17b 20 and 21) detected 85.5% of CF alleles. Haplotypes for eight diallelic and three microsatellite markers have been characterized for the common, a few rare and novel Greek mutations. Results of 165 prenatal diagnoses (including 49 due to bowel hyperechogenicity), testing a total of 41 different parental genotypes, are reported. One hundred and sixteen prenatal tests resulted in 22 affected, 59 heterozygous, 34 normal fetuses and one incomplete diagnosis. Of the 49 echogenic bowel fetuses, 3 were heterozygotes. Carrier screening was initiated, with emphasis on individuals and couples in high‐risk groups – with a family history of CF, one partner with CF, and couples with male infertility seeking in vitro fertilization (IVF). Mutation analysis on 672 individuals (120 couples, 91 unaffected CF siblings, 283 CF family relatives and 58 general population subjects), identified a total of 176 heterozygotes and 7 couples where both partners were CF heterozygotes. Prenatal diagnosis was performed in 4 cases and 3 were counseled on the availability of a prenatal test.

RASSF1A in maternal plasma as a molecular marker of preeclampsia

This study aimed to quantitate cell free (cf) and cell free fetal (cff) DNA in maternal plasma by determining RASSF1A levels before and after enzyme digestion in women who subsequently developed preeclampsia (PE) and compare them with uncomplicated pregnancies.

Proteomic analysis of amniotic fluid in pregnancies with Klinefelter syndrome foetuses

Klinefelter syndrome is a sex chromosomal abnormality (47, XXY karyotype), occurring approximately in 1 in 1000 male live births. In the present study proteomic analysis was performed in twelve 2nd trimester amniotic fluid samples, eight coming from pregnancies with normal males and four with Klinefelter syndrome foetuses, as shown by routine prenatal cytogenetic analysis. Samples were analysed by 2-DE, coupled with MALDI-TOF-MS analysis. Three proteins (Ceruloplasmin, Alpha-1-antitrypsin and Zinc-alpha-2-glycoprotein) were found to be up-regulated in samples obtained from pregnancies with Klinefelter syndrome foetuses, whereas four proteins (Apolipoprotein A-I, Plasma retinol-binding protein, Gelsolin, and Vitamin D-binding protein) were down regulated when compared to proteins detected in samples from normal foetuses. The differential expression of Ceruloplasmin, Apolipoprotein A-I and Plasma retinol-binding protein was further confirmed by immunoblotting. Since these proteins are likely to cross the placenta barrier and be detected in maternal plasma they could be used as biomarkers for the non-invasive prenatal diagnosis of Klinefelter syndrome.

Evidence for a Common Ethnic Origin of Cystic Fibrosis Mutation 3120+1G→A in Diverse Populations

Part of this work was supported by an Alexander von Humboldt Foundation grant (to E.-H.A.E.-H.); by IGA MZ CR grants 2899-5, 3526-3, and 4124-3, GA CR grant 301/66/1606; and Barrande grant 970157 (all to M.M.).

Rapid and accurate quantitation of Hb Bart's and Hb H using weak cation exchange high performance liquid chromatography: correlation with the alpha-thalassemia genotype.

The Bio-Rad Variant Hemoglobin testing system is an automated high performance liquid chromatography analyzer marketed with a beta-thalassemia short program to quantify Hbs F and A2, and assist in detecting Hbs A, S, D, C, and E. Although the two hemoglobins present in Hb H disease, Hb Barts and Hb H, are separated by the system, they are not quantitated. In this study we modified the beta-thalassemia short program in order to facilitate quantitation of Hb Barts and Hb H. Blood samples from 60 patients with Hb H disease, with various underlying genotypes, were studied. Analyses were performed on the day of blood collection or on hemolysates stored at -80 degrees C in cyanide or carbomonoxy forms. The mean sum of Hb Barts and Hb H levels in all patients was found to be 12% (range 1.8-35%). Patients with nondeletional mutations (or association of alpha(0) deletion and nondeletional mutations) had notably higher Hb Barts and Hb H levels when compared to patients with deletional genotypes.

Early non-invasive detection of fetal Y chromosome sequences in maternal plasma using multiplex PCR.

OBJECTIVEnClinical indications for fetal sex determination include risk of X-linked disorders, a family history of conditions associated with ambiguous development of the external genitalia, and some fetal ultrasound findings. It is usually performed in the first trimester from fetal material obtained through CVS and is associated with an approximately 1% risk of miscarriage. Ultrasound fetal sex determination is often performed after 11 weeks of gestation. This study aims to validate a reliable method for non-invasive prenatal diagnosis of fetal gender using maternal plasma cell-free fetal DNA (cffDNA) for fetal sex assessment in the first trimester of pregnancy and test its clinical utility in the diagnosis of potentially affected pregnancies in carriers of X-linked disorders.nnnSTUDY DESIGNnIn the validation study, blood samples from 100 pregnant women at 6-11 weeks of gestation were analysed. In the clinical study, 17 pregnancies at risk of having an affected fetus were tested. 7 ml of maternal blood in EDTA were obtained and cffDNA was extracted using a commercially available kit. DNA was enzymatically digested using a methylation sensitive endonuclease (AciI) to remove maternal unmethylated sequences of the RASSF1A gene. A multiplex PCR was performed for the simultaneous amplification of target sequences of SRY and DYS14 from chromosome Y, along with RASSF1A and ACTB sequences. Amplification of these loci indicates fetal gender, confirms the presence of cffDNA and allows assessment of digestion efficiency.nnnRESULTSnAfter establishing the appropriate experimental conditions, validation studies were successful in all 100 cases tested with no false negative or false positive results. Y chromosome-specific sequences were detected in 68 samples, and 32 cases were diagnosed as female based on the amplification of RASFF1A sequences only, in the absence of ACTB. In the clinical studies, fetal sex was correctly diagnosed in 16 pregnancies, and one case was reported as inconclusive.nnnCONCLUSIONSnFetal sex assessment by detecting Y chromosome sequences in maternal blood can be routinely used from the 6th week of gestation. Reliable fetal sex determination from maternal blood in the 1st trimester of gestation can avoid conventional invasive methods of prenatal diagnosis.