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J Zielenski

Publications and source records attributed to J Zielenski.

At least 19 recordsLinked to original sources
PubMed1998

Analysis of the CFTR gene in Turkish cystic fibrosis patients: identification of three novel mutations (3172delAC, P1013L and M1028I).

In order to determine the spectrum of cystic fibrosis (CF) mutations in the Turkish population, a complete coding region of the cystic fibrosis transmembrane conductance regulator (CFTR) gene including exon-intron boundaries, on 122 unrelated CF chromosomes from 73 Turkish CF families was analysed by denaturing gradient gel electrophoresis and multiplex heteroduplex analysis on MDE gel matrix. In addition to 15 previously reported mutations and 12 polymorphisms, three novel mutations, namely 3172delAC, P1013L and M1028I, were detected. DeltaF508 was found to be present on 18.8% of CF chromosomes. The second most common mutation was 1677delTA, with a frequency of 7.3%, followed by G542X and 2183AA-->G mutations, with frequencies of 4.9%. These four most common mutations in Turkish CF population account for approximately 36% of mutations. This study could only detect 52.5% of disease-causing mutations in this population; 47.5% of CF alleles remain to be identified, reflecting the high molecular heterogeneity of the Turkish population.

Adenine↗
PubMed1998

Heterogeneity of reproductive tract abnormalities in men with absence of the vas deferens: role of cystic fibrosis transmembrane conductance regulator gene mutations.

OBJECTIVE: To determine if the types of reproductive tract abnormalities linked to absence of the vas deferens varies with the cystic fibrosis transmembrane conductance regulator (CFTR) genotype. DESIGN: Prospective data gathering. SETTING: University infertility clinic. PATIENT(S): Forty-six infertile men with absence of the scrotal vas deferens and no signs of cystic fibrosis. INTERVENTION(S): All had blood taken for CFTR gene analysis, 33 had scrotal ultrasounds, and 25 had transrectal ultrasounds. MAIN OUTCOME MEASURE(S): The frequency of testicular, seminal vesicle, and ampullae of the vas deferens malformations was compared between subgroups of men with two, one, or no CFTR gene mutations. RESULT(S): None (0 of 21) of the men with at least one CFTR gene mutations had normal ampullae of the vas or seminal vesicles bilaterally. Two (50%) of 4 men with no CFTR gene mutations had normal ampullae of the vas deferens bilaterally, and 50% had normal bilateral seminal vesicles (statistically significantly different). There was no correlation between testicular malformations and CFTR genotype. CONCLUSION(S): This study indicates that the severity of the malformations in the testis is unrelated to the CFTR genotype, whereas the frequency and severity of wolffian duct malformations are related directly to the CFTR genotype.

Cystic Fibrosis Transmembrane Conductance Regulato↗
PubMed1998

Uncertainty in the diagnosis of cystic fibrosis: possible role of in vivo nasal potential difference measurements.

The diagnosis of cystic fibrosis (CF) is not always certain, despite extensive clinical evaluation, multiple sweat chloride tests, and genotype analysis. We hypothesized that nasal transepithelial potential difference measurements have a useful role in this situation. In 11 patients without an established diagnosis of CF, results of simultaneous nasal potential difference (PD) and sweat chloride measurements were compared with those from control subjects, obligate CF heterozygotes, and patients with a confirmed diagnosis of CF. Two patients conformed to the PD profile for CF patients, whereas nine had values corresponding to those of the healthy control subjects. Subsequently the 5-thymidine (IVS8-5T) CF gene variant was identified in the two patients with abnormal PD measurements.

Adolescent↗
PubMed1997

Higher proportion of intact exon 9 CFTR mRNA in nasal epithelium compared with vas deferens.

The 5-thymidine (5T) variant of the cystic fibrosis transmembrane conductance regulator (CFTR) intron 8 polypyrimidine tract (IVS8-T tract) is the most frequent CFTR gene alteration identified in men with congenital bilateral absence of vas deferens (CBAVD). This alternative splicing variant gives rise to two transcripts, one normal with exon 9 intact and the other with in-frame deletion of exon 9. That CBAVD men usually have none of the other clinical signs of classical cystic fibrosis (CF) suggests less functional CFTR is produced in the reproductive tract than in other CF-associated organs. Nasal epithelia and segments of vas deferens were obtained from healthy, previously vasectomized men who presented for vasectomy reversal. Quantitative RT-PCR was performed on these specimens, with the region of CFTR cDNA spanning exon 9 amplified. For both nasal and vasal tissues, a strong positive correlation was found between the length of the IVS8-T tract and the proportion of mRNA with exon 9 intact. In addition, within the same subject, a significantly higher level of transcripts lacking exon 9 was found in vas deferens than nasal epithelia, regardless of the IVS8-T genotype. These findings suggest that the splicing of CFTR precursor mRNA is less efficient in vasal epithelia compared with respiratory epithelia. Thus, differential splicing efficiency between the various tissues which express CFTR provides one possible explanation for the reproductive tract abnormalities observed in infertile men with CFTR gene alterations but without other clinical manifestations of CF.

Alleles↗
PubMed1996

Haplotype analysis of 94 cystic fibrosis mutations with seven polymorphic CFTR DNA markers.

We have analyzed 416 normal and 467 chromosomes carrying 94 different cystic fibrosis (CF) mutations with polymorphic genetic markers J44, IVS6aGATT, IVS8CA, T854, IVS17BTA, IVS17BCA, and TUB20. The number of mutations found with each haplotype is proportional to its frequency among normal chromosomes, suggesting that there is no preferential haplotype in which mutations arise and thus excluding possible selection for specific haplotypes. While many common mutations in the worldwide CF population showed absence of haplotype variation, indicating their recent origins, some mutations were associated with more than one haplotype. The most common CF mutations, delta F508, G542X, and N1303K, showed the highest number of slippage events at microsatellites, suggesting that they are the most ancient CF mutations. Recurrence was probably the case for 9 CF mutations (R117H, H199Y, R347YH, R347P, L558S, 2184insA, 3272-26A-->G, R1162X, and 3849 + 10kbC-->T). This analysis of 94 CF mutations should facilitate mutation screening and provides useful data for studies on population genetics of CF.

Cystic Fibrosis↗
PubMed1996

Congenital absence of the vas deferens: a mild form of cystic fibrosis.

Genetic diseases presenting with different phenotypes are generally classified as distinct disorders before their molecular defect is revealed, as exemplified by the recent advance in understanding of the molecular biology of cystic fibrosis and an obstructive form of infertility, known as congenital absence of the vas deferens. The majority of men with congenital absence of the vas deferens have a defect in both copies of the CFTR gene and therefore represent a distinct phenotypic form of cystic fibrosis. These developments help us to gain new insight into the genetic basis of phenotypic variability and the possible contributing mechanisms in cystic fibrosis. Some of the lessons learned from the relationship between cystic fibrosis and congenital absence of the vas deferens may be useful in the understanding of other genetic disorders.

Congenital Abnormalities↗
PubMed1995

Identification of six mutations (R31L, 441delA, 681delC, 1461ins4, W1089R, E1104X) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

Six new mutations have been identified in the CFTR gene. These mutations, representing three different categories--missense (R31L, W1098R), nonsense (E1104X), and frameshift (441delA, 681delC, 1461ins4)--are located in exons 2, 4, 5, 9, and 17b of the gene and presumed to cause cystic fibrosis (CF) in patients. All these mutations are probably rare in the population, as no additional examples were found for any of them in a cohort of 545 CF patients. Our study also revealed a benign sequence variation (3499 + 45T-->C) in intron 17b.

Adult↗
PubMed1995

Correlation of sweat chloride concentration with classes of the cystic fibrosis transmembrane conductance regulator gene mutations.

OBJECTIVE: To compare differences in epithelial chloride conductance according to class of mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. METHODS: We evaluated the relationship between the functional classes of CFTR mutations and chloride conductance using the first diagnostic sweat chloride concentration in a large cystic fibrosis (CF) population. RESULTS: There was no difference in sweat chloride value value between classes of CFTR mutations that produce no protein (class I), fail to reach the apical membrane because of defective processing (class II), or produce protein that fails to respond to cyclic adenosine monophosphate (class III). Those mutations that produce a cyclic adenosine monophosphate-responsive channel with reduced conductance (class IV) were associated with a significantly lower, intermediate sweat chloride value. However, patients with the mutations that cause reduced synthesis or partially defective processing of normal CFTR (class V) had sweat chloride concentrations similar to those in classes I to III. CONCLUSION: Studies of differences in chloride conductance between functional classes of CFTR mutations provide insight into phenotypic expression of the disease.

Child↗
PubMed1995

Skipping of exon 12 as a consequence of a point mutation (1898 + 5G-->T) in the cystic fibrosis transmembrane conductance regulator gene found in a consanguineous Chinese family.

A point mutation (1898 + 5G-->T) located five base pairs downstream from the donor splice site in intron 12 of the CFTR gene has been identified in a consanguineous CF patient of Chinese origin. To determine if this nucleotide substitution could affect mRNA splicing, PCR analysis was performed with RNA isolated from the lymphoblastoid cell line of the mother of the deceased patient. While exon 12-minus transcript was detected in this sample, it was also found in individuals without 1898 + 5G-->T, albeit in a smaller proportion. Using a sequence polymorphism associated with each of the two alleles in the mother, however, we showed that mutant transcript was almost exclusively produced by the 1898 + 5G-->T allele. Skipping of exon 12 would result in the deletion of 29 amino acids from the first nucleotide binding domain of CFTR, rendering the protein non-functional. The possibility of a low level (< or = 2.5%) of normal transcript from the mutant allele cannot be excluded and it may explain the pancreatic sufficient phenotype of the patient. The 1898 + 5G-->T mutation was found in two other CF patients of Chinese origin, but it was not detected in 192 CF chromosomes of Caucasian origin and 30 other chromosomes from Chinese individuals without a family history of CF.

Base Sequence↗
PubMed1995

Cystic fibrosis: genotypic and phenotypic variations.

Cystic fibrosis (CF) is a common genetic disorder in the Caucasian population. The gene was identified in 1989 on the basis of its map location on chromosome 7. The encoded gene product, named cystic fibrosis transmembrane conductance regulator (CFTR), corresponds to a cAMP-regulated chloride channel found almost exclusively in the secretory epithelial cells. Although the major mutation that results in a single amino acid deletion (F508) accounts for 70% of the disease alleles, more than 550 additional mutant alleles of different forms have been detected. Many of these mutations can be divided into five general classes in terms of their demonstrated or presumed molecular consequences. In addition, a good correlation has been found between CFTR genotype and one of the clinical variables--pancreatic function status. An unexpected finding, however, is the documentation of CFTR mutations in patients with atypical CF disease presentations, including congenital absence of vas deferens and several pulmonary diseases. Thus, the implication of CFTR mutation is more profound than CF alone.

Alternative Splicing↗
PubMed1993

Chemical syntheses of Trolox conjugates which protect human ventricular myocytes against in situ-generated oxyradicals.

Synthetic conjugates of the antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethyl chroman-2-carboxylic acid) have been prepared by coupling it with 1-ethyl-3-(3-dimethyl-amino-propyl) carbodiimide hydrochloride either to p-aminophenyl-beta-D-lactopyranoside, or to higher molecular weight ligands such as dextran and polylysine. Compared to Trolox and on a mole to mole basis, dextran-Trolox is almost equally active, while lactosylphenyl- and polylysine-Trolox conjugates are distinctly more active in preventing the damage on human ventricular myocytes by oxyradicals generated from xanthine oxidase-hypoxanthine. Listed in order of decreasing cytoprotective activity, they are: lactosylphenyl-Trolox >> polylysine-Trolox > Trolox > dextran-Trolox. Thus, Trolox can be chemically modified by coupling it to one of a number of ligands and, in some cases, with resultant increases in its ability to protect human ventricular myocytes from oxyradical damage.

Antioxidants↗
PubMed1993

Analysis of CFTR transcripts in nasal epithelial cells and lymphoblasts of a cystic fibrosis patient with 621 + 1G-->T and 711 + 1G-->T mutations.

We have analyzed the CFTR mRNA populations in a cystic fibrosis patient heterozygous for the 621 + 1G-->T and 711 + 1G-->T mutations. Total RNA isolated from the nasal epithelial cells and Epstein-Barr virus-transformed lymphoblasts derived from this patient was reversely transcribed and a region extending from exon 3 to exon 7 of the gene was amplified by the polymerase chain reaction and analyzed. Three abnormal products were identified, suggesting the presence of three aberrant transcripts, and their profiles were identical in both cell types. Two of the products were found to be missing either exon 4 or exon 5 as anticipated from the transcripts from the 621 + 1G-->T or 711 + 1G-->T alleles, respectively. The third product was apparently derived from an alternatively spliced mRNA species in the absence of the nominal splice site (in 621 + 1G-->T) through the use of a cryptic splice donor sequence (TT528/GTGAGG) within exon 4. Although reading frames appeared to be preserved in all three putative transcripts, significant portions of the presumed first and second transmembrane spans as well as the immediately following cytoplasmic domain would be deleted from the mutant CFTR polypeptides, if made. These observations are consistent with a loss of CFTR function in this cystic fibrosis patient.

Alleles↗