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T Casals

Publications and source records attributed to T Casals.

At least 37 records · Page 2Linked to original sources
PubMed1997

SSCP analysis: a blind sensitivity trial.

Studies of the sensitivity of SSCP analysis usually have been performed under conditions contrary to the rules of quality control trials and have produced widely different results. We have performed a blind trial of the sensitivity of SSCP analysis for the detection of mutations in fragments up to 500 bp in length under a fixed single set of electrophoretic conditions. The mutation detection rate was 84%. In addition, we have identified a second mutation in nine samples. All these mutations are polymorphisms, including a novel polymorphism 1248 + 52T/C first reported in the present work.

Cystic Fibrosis Transmembrane Conductance Regulato↗
PubMed1997

Missense mutation R1066C in the second transmembrane domain of CFTR causes a severe cystic fibrosis phenotype: study of 19 heterozygous and 2 homozygous patients.

We report the clinical features of 21 unrelated cystic fibrosis (CF) patients from Portugal and Spain, who carry the mutation R1066C in the CFTR gene. The current age of the patients was higher in the R1066C/any mutation group (P < 0.01), as compared to the deltaF508/deltaF508 group. Poor values for lung radiological involvement (Chrispin-Norman) and general status (Shwachman-Kulcycki) were observed in the R1066C/any mutation group (P < 0.005 and P < 0.0004). A slightly, but not significantly worse lung function was found in the R1066C/any mutation group when compared with the deltaF508/deltaF508 patients. No significant differences were detected regarding the age at diagnosis, sweat Cl-values, or percentiles of height and weight between the two groups. Neither were significant differences observed regarding sex, meconium ileus (4.7% vs. 11.1%), dehydration (10.5% vs. 14.7%), or pancreatic insufficiency (PI) (100% vs. 97.8%). The proportion of patients with lung colonization by bacterial pathogens was slightly, but not significantly higher in the R1066C/any mutation group (70.0%), as compared with the deltaF508/deltaF508 group (57.5%). Other clinical complications were significantly more frequent in the R1066C/any mutation patients(P < 0.02) than in the deltaF508/deltaF508 group. The two homozygous R1066C/R1066C patients died at the ages of 3 months and 7 years. The data presented in this study clearly demonstrate that the R1066C mutation is responsible for a severe phenotype similar to that observed in homozygous deltaF508 patients. The poor clinical scores and complications of patients with the R1066C mutation are probably related to their slightly longer survival.

Adolescent↗
PubMed1997

High heterogeneity for cystic fibrosis in Spanish families: 75 mutations account for 90% of chromosomes.

We have analyzed 640 Spanish cystic fibrosis (CF) families for mutations in the CFTR gene by direct mutation analysis, microsatellite haplotypes, denaturing gradient gel electrophoresis, single-strand conformation analysis and direct sequencing. Seventy-five mutations account for 90.2% of CF chromosomes. Among these we have detected seven novel CFTR mutations, including four missense (G85V, T582R, R851L and F1074L), two nonsense (E692X and Q1281X) and one splice site mutation (711+3A-->T). Three variants, two in intronic regions (406-112A/T and 3850-129T/C) and one in the coding region (741C/T) were also identified. Mutations G85V, T582R, R851L, E692X and Q1281X are severe, with lung and pancreatic involvement; 711+3A-->T could be responsible for a pancreatic sufficiency/insufficiency variable phenotype; and F1074L was associated with a mild phenotype. These data demonstrate the highest molecular heterogeneity reported so far in CF, indicating that a wide mutation screening is necessary to characterize 90% of the Spanish CF alleles.

Cystic Fibrosis↗
PubMed1996

Prenatal diagnosis of cystic fibrosis in a highly heterogeneous population.

Cystic fibrosis (CF) is the most common autosomal recessive disease in Caucasian populations. The Spanish CF population is highly heterogeneous, with more than 70 different mutations causing CF. Since the CFTR gene was cloned, we have performed 81 prenatal diagnoses for 74 couples. Sixty-nine cases had a high risk (1/4) for CF and 12 presented a lower risk (1/240). Direct analysis was possible in 36 cases (44.4 per cent); it was necessary to combine mutation analysis with polymorphic markers in 24 cases (29.6 per cent); mutation analysis and microvillar enzymatic (MVE) analysis were combined in five cases (6.1 per cent); and in 16 cases (19.8 per cent), only indirect analysis was possible. Nine different mutations were detected in this series of families: 621 + 1G -> T, delta F508, 1609delCA, G542X, G551D, 1949del84, R1162X, W1282X, and N1303K. Another ten mutations were identified in these samples after prenatal diagnosis (1811 + 1.6kbA -> G, 711 + 1G -> T, 2869insG, G85E, 2176insC, delta I507, 3272-26A -> G, Q890X, R1066C, and 4005 + 1G -> A). Our current strategy for molecular diagnosis of CF in the Spanish population is based, as a first step, on direct analysis for the two most frequent mutations (delta F508 and G542X) and indirect analysis using the intragenic markers IVS8CA, IVS17BTA, and IVS17BCA. The second step consists of screening for the mutations already associated with the CFTR microsatellite haplotypes. The third step is a specific search for unknown mutations. While actual diagnostic methods are not automatic and robust enough for heterogeneous populations, the diagnostic strategy outlined provides rapid, accurate, and reliable prenatal diagnosis for the majority of couples.

Amniotic Fluid↗
PubMed1996

Thirteen cystic fibrosis patients, 12 compound heterozygous and one homozygous for the missense mutation G85E: a pancreatic sufficiency/insufficiency mutation with variable clinical presentation.

To study the severity of mutation G85E, located in the first membrane spanning domain of the CFTR gene, we studied the clinical features of 13 Spanish patients with cystic fibrosis (CF) carrying this mutation. G85E accounts for about 1% of Spanish CF alleles. One patient was homozygous G85E/G85E and the rest were compound heterozygotes for G85E and other mutations (delta F508 nine patients, delta I507 two patients, and 712-1G > T one patient). The characteristics of the pooled G85E/any mutation group were compared with those of 30 delta F508 homozygotes. Mean age at diagnosis and percentage of ideal height for age were higher in the G85E/any mutation group (4.2 (SD 4.7) v 2.4 (SD 2.3), p < 0.05, and 102.8 (SD 4.7) v 97.8 (SD 4.1), p < 0.01), both probably related to the greater prevalence of pancreatic sufficiency (70% v 0%, p < 0.01). The G85E homozygote was pancreatic sufficient. Sweat sodium levels were slightly higher, and salt loss related problems more frequent, in the G85E/any group. Two of the G85E patients died of respiratory failure aged 6 and 14 years. Striking discordance in the phenotype was observed in two pairs of sibs, one of them dizygotic twins, suggesting that factors, genetic and environmental, other than CFTR genotype are important in determining CF phenotype.

Child↗
PubMed1995

Mutations in the cystic fibrosis gene in patients with congenital absence of the vas deferens.

BACKGROUND: Congenital bilateral absence of the vas deferens (CBAVD) is a form of male infertility in which mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene have been identified. The molecular basis of CBAVD is not completely understood. Although patients with cystic fibrosis have mutations in both copies of the CFTR gene, most patients with CBAVD have mutations in only one copy of the gene. METHODS: To investigate CBAVD at the molecular level, we have characterized the mutations in the CFTR gene in 102 patients with this condition. None had clinical manifestations of cystic fibrosis. We also analyzed a DNA variant (the 5T allele) in a noncoding region of CFTR that causes reduced levels of the normal CFTR protein. Parents of patients with cystic fibrosis, patients with types of infertility other than CBAVD, and normal subjects were studied as controls. RESULTS: Nineteen of the 102 patients with CBAVD had mutations in both copies of the CFTR gene, and none of them had the 5T allele. Fifty-four patients had a mutation in one copy of CFTR, and 34 of them (63 percent) had the 5T allele in the other CFTR gene. In 29 patients no CFTR mutations were found, but 7 of them (24 percent) had the 5T allele. In contrast, the frequency of this allele in the general population was about 5 percent. CONCLUSIONS: Most patients with CBAVD have mutations in the CFTR gene. The combination of the 5T allele in one copy of the CFTR gene with a cystic fibrosis mutation in the other copy is the most common cause of CBAVD: The 5T allele mutation has a wide range of clinical presentations, occurring in patients with CBAVD or moderate forms of cystic fibrosis and in fertile men.

Alleles↗
PubMed1995

Extensive analysis of 40 infertile patients with congenital absence of the vas deferens: in 50% of cases only one CFTR allele could be detected.

Mutations in the cystic fibrosis (CF) conductance transmembrane regulator (CFTR) gene have been detected in patients with CF and in males with infertility attributable to congenital bilateral absence of the vas deferens (CBAVD). Thirty individuals with CBAVD and 10 with congenital unilateral absence of the vas deferens (CUAVD) were analyzed by single-strand conformation analysis and denaturing gradient gel electrophoresis for mutations in most of the CFTR gene. All 40 individuals were pancreatic sufficient, but twenty patients had recurrent or sporadic respiratory infections, asthma/asthmatic bronchitis, and/or rhino-sinusitis. Agenesia or displasia of one or both seminal vesicles was detected in 30 men and other urogenital malformations were present in six subjects. Among the 40 samples, we identified 13 different CFTR mutations, two of which were previously unknown. One new mutation in exon 4 was the deletion of glutamic acid at codon 115 (delta E115). A second new mutation was found in exon 17b, viz., an A --> C substitution at position 3311, changing lysine to threonine at codon 1060 (K1060T). CFTR mutations were detected in 22 out of 30 (73.3%) CBAVD patients and in one out of 10 (10%) CUAVD individuals, showing a significantly lower incidence of CFTR mutations in CBAVD/CUAVD patients (P << 0.0001), compared with that found in the CF patient population. Only three CBAVD patients were found with more than one CFTR mutation (delta F508/L206W, delta F508/R74W + D1270N, R117H/712-1G --> T), highlighting L206W, R74W/D1270N, and R117H as benign CF mutations. Sweat electrolyte values were increased in 76.6% of CBAVD patients, but three individuals without CFTR mutations had normal sweat electrolyte levels (10% of the total CBAVD patients), suggesting that factors other than CFTR mutations are involved in CBAVD. The failure to identify a second mutation in exons and their flanking regions of the CFTR gene suggests that these mutations could be located in introns or in the promoter region of CFTR. Such mutations could result in CFTR levels below the minimum 6%-10% necessary for normal protein function.

Adolescent↗
PubMed1995

A novel donor splice site in intron 11 of the CFTR gene, created by mutation 1811+1.6kbA-->G, produces a new exon: high frequency in Spanish cystic fibrosis chromosomes and association with severe phenotype.

mRNA analysis of the cystic fibrosis transmembrane regulator (CFTR) gene in tissues of cystic fibrosis (CF) patients has allowed us to detect a cryptic exon. The new exon involves 49 base pairs between exons 11 and 12 and is due to a point mutation (1811+1.6kbA-->G) that creates a new donor splice site in intron 11. Semiquantitative mRNA analysis showed that 1811+1.6kbA-->G-mRNA was 5-10-fold less abundant than delta F508 mRNA. Mutation 1811+1.6kbA-->G was found in 21 Spanish and 1 German CF chromosomes, making it the fourth-most-frequent mutation (2%) in the Spanish population. Individuals with genotype delta F508/1811+1.6kbA-->G have only 1%-3% of normal CFTR mRNA. This loss of 97% of normal CFTR mRNA must be responsible for the pancreatic insufficiency and for the severe CF phenotype in these patients.

Adolescent↗
PubMed1994

Analysis of the CFTR gene in the Spanish population: SSCP-screening for 60 known mutations and identification of four new mutations (Q30X, A120T, 1812-1 G-->A, and 3667del4).

In order to determine the spectrum of CF mutations in the Spanish population, we have analysed 40 unrelated Spanish CF patients, with at least one chromosome negative for mutations delta F508, G542X, and N1303K. Exons 1-7,10-14a,15,16,17b,18-21 of the CFTR gene were studied by Single Strand Conformation Polymorphism (SSCP) analysis, using 60 known CF mutations as controls. SSCP screening allowed us to detect 28 different mutations in 52 CF chromosomes, and to identify four new mutations (Q30X in exon 2, A120T in exon 4, 1812-1G-->A in intron 11 and and 3667del4 in exon 19). Further analysis of the four new mutations in a total of 950 Spanish CF chromosomes showed a final frequency of 0.4%, 0.1%, 0.1%, and 0.1% for 1812-1G-->A,Q30X, A120T, and 3667del4, respectively. No mutations were detected in exons 1, 3, 14a, 16, and 18. We have also detected 10 intragenic polymorphisms and DNA sequence variants and have analysed their frequencies in our population. The total of 28 mutations identified in the 80 CF chromosomes highlight the molecular heterogeneity of CF in the Spanish population.

Base Sequence↗
PubMed1994

Analysis of the CFTR gene confirms the high genetic heterogeneity of the Spanish population: 43 mutations account for only 78% of CF chromosomes.

We have analysed 972 unrelated Spanish cystic fibrosis patients for 70 known mutations. Analysis was performed on exons 1, 2, 3, 4, 5, 6a, 6b, 7, 10, 11, 12, 13, 14a, 14b, 15, 16, 17b, 18, 19, 20 and 21 of the cystic fibrosis transmembrane regulator gene using single strand conformation polymorphism analysis and denaturing gradient gel electrophoresis. The major mutation delta F508 accounts for 50.6% of CF chromosomes, whereas another 42 mutations account for 27.6% of CF chromosomes, with 21.8% of Spanish CF chromosomes remaining uncharacterized. At present, we have identified 36 mutations that have frequency of less than 1% and that are spread over 15 different exons. This indicates that, in the Spanish population, with the exception of delta F508 (50.6%) and G542X (8%), the mutations are not concentrated in a few exons of the gene nor are there any predominating mutations. This high degree of genetic heterogeneity is mainly a result of the different ethnic groups that have populated Spain and of the maintenance of separated population sets (Basques, Arab-Andalusian, Mediterranean, Canarian and Gallician). The high proportion of CF chromosomes still unidentified (21.8%) together with association analysis with intragenic markers suggest that at least 100 different mutations causing CF are present in our population.

Cystic Fibrosis↗
PubMed1994

The origin of the major cystic fibrosis mutation (delta F508) in European populations.

delta F508 is the most frequent cystic fibrosis (CF) mutation and accounts for approximately 70% of CF chromosomes worldwide. Three highly polymorphic microsatellite markers have been used to study the origin and evolution of delta F508 chromosomes in Europe. Haplotype data demonstrate that delta F508 occurred more than 52,000 years ago, in a population genetically distinct from any present European group, and spread throughout Europe in chronologically distinct expansions, which are responsible for the different frequencies of delta F508 in Europe.

Biological Evolution↗
PubMed1994

Molecular and clinical analyses of cystic fibrosis in the south of Spain.

We report molecular and clinical analyses in 71 unrelated patients with cystic fibrosis (CF) from Andalusia (South of Spain). Direct mutation analysis of six mutations of the CFTR gene (delta F508, G542X, R1162X, N1303K, W1182X and 1949de184) was performed. The proportion of CF chromosomes with the above-mentioned mutations was 58.5%. Haplotype analysis was performed with the marker/enzyme pairs XV2C/TaqI and KM19/PstI. A particular haplotype has been found associated with each of the studied mutations, while the pooled data for the unknown mutations are not associated with any particular haplotype. This lack of association indicates that there will not be a single predominant mutation amongst the other CF chromosomes. To assess the relationship between genotype and phenotype in these patients, we correlated the pancreatic status and the occurrence of chronic Pseudomona aeruginosa infection with the observed genotype. Pancreatic insufficiency was present in all patients in whom the analyzed mutations were found to be homozygous or compound heterozygous. We also found a higher rate of Pseudomonas colonization in the group of patients in whom the genotype was homozygous or compound heterozygous for the analysed mutations when compared with the group of patients with a different genotype, but the difference was not statistically significant.

Chi-Square Distribution↗
PubMed1994

A cystic fibrosis patient homozygous for the new frameshift mutation 936delTA: description and clinical data.

We report the identification of a new frameshift mutation (936delTA) in exon 6b of the CFTR gene. In the screening of 486 unrelated Spanish CF patients we found a patient homozygous for 936delTA (with consanguineous parents) and a patient heterozygous for delta F508 and 936delTA. Genotype-phenotype correlation studies showed that 936delTA is associated with pancreatic insufficiency and chronic pulmonary colonisation.

Base Sequence↗
PubMed1994

Independent origins of cystic fibrosis mutations R334W, R347P, R1162X, and 3849 + 10kbC-->T provide evidence of mutation recurrence in the CFTR gene.

Microsatellite analysis of chromosomes carrying particular cystic fibrosis mutations has shown different haplotypes in four cases: R334W, R347P, R1162X, and 3849 + 10kbC-->T. To investigate the possibility of recurrence of these mutations, analysis of intra- and extragenic markers flanking these mutations has been performed. Recurrence is the most plausible explanation, as it becomes necessary to postulate either double recombinations or single recombinations in conjunction with slippage at one or more microsatellite loci, to explain the combination of mutations and microsatellites if the mutations arose only once. Also in support of recurrence, mutations R334W, R347P, R1162X, and 3849 + 10kbC-->T involve CpG dinucleotides, which are known to have an increased mutation rate. Although only 15.7% of point mutations in the coding sequence of CFTR have occurred at CpG dinucleotides, approximately half of these CpG sites have mutated at least once. Specific nucleotide positions of the coding region of CFTR, distinct from CpG sequences, also seem to have a higher mutation rate, and so it is possible that the mutations observed are recurrent. G-->A transitions are the most common change found in those positions involved in more than one mutational event in CFTR.

Base Sequence↗
PubMed1993

Cystic fibrosis in Spain: high frequency of mutation G542X in the Mediterranean coastal area.

We have determined the frequency of deletion delta F508 and mutation G542X, a nonsense mutation in exon 11 of the cystic fibrosis (CF) gene, in a sample of 400 Spanish CF families. Mutation G542X represents 8% of the total number of CF mutations in Spain, making it the second most common mutation after the delta F508 deletion, which accounts for 48% of CF chromosomes. G542X has a higher frequency in the Mediterranean coastal area (14%) and in the Canary Islands (25%). About 70% of G542X chromosomes are from Andalucia, Múrcia, Valencia, Catalunya and the Canary Islands. The delta F508 deletion has its highest frequency in the Basque Country (83%). Mutation G542X is associated with the same rare haplotype that is found in association with the delta F508 mutation. The haplotype homogeneity found for G542X, even when intragenic microsatellites (IVS8CA, IVS17BTA and IVS17BCA) are considered, allows us to postulate that this mutation arose from a single mutational event. The geographic distribution of mutations delta F508 and G542X suggests that delta F508 was present in the Iberian Peninsula before the Indo-European invasions, and that G542X was introduced into Spain, via the Mediterranean Sea, probably by the Phoenicians, between 2500 and 3000 years ago.

Base Sequence↗
PubMed1993

Uniparental inheritance of microsatellite alleles of the cystic fibrosis gene (CFTR): identification of a 50 kilobase deletion.

More than 250 mutations have been detected in the cystic fibrosis (CF) transmembrane regulator (CFTR) gene, most of which are single point mutations or small deletions or insertions of a few nucleotides. Here we report the first large deletion identified in the CFTR gene, which involves 50 kb in two stretches of DNA: one of 10 kb from exon 4 to exon 7, and another of 40 kb, spanning exons 11 to 18. The deletion has been detected via uniparental inheritance of CFTR microsatellite alleles (IVS17BTA and IVS17BCA) in 3 independent CF families. Clinical status of the 3 CF patients, of which two have the delta F508 mutation as the other CF allele, suggests that this mutation is responsible for a severe clinical phenotype, indistinguishable from homozygous delta F508 patients. The deletion detected here suggests that other large, but less complex molecular defects could also exist in the CFTR gene.

Adult↗