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M Claustres

Publications and source records attributed to M Claustres.

At least 37 records · Page 2Linked to original sources
PubMed2000

A naturally occurring sequence variation that creates a YY1 element is associated with increased cystic fibrosis transmembrane conductance regulator gene expression.

We have identified previously a novel complex mutant allele in the cystic fibrosis transmembrane conductance regulator (CFTR) gene in a patient affected with cystic fibrosis (CF). This allele contained a mutation in CFTR exon 11 known to cause CF (S549R(T>G)), associated with the first alteration described so far in the minimal CFTR promoter region (-102T>A). Studies on genotype-phenotype correlations revealed striking differences between patients carrying mutation (S549R(T>G)) alone, who had a severe disease, and patients carrying the complex allele (-102(T>A)+S549R(T>G)), who exhibited milder forms of CF. We thus postulated that the sequence change (-102T>A) may attenuate the effects of the severe (S549R(T>G)) mutation through regulation of CFTR expression. Analysis of transiently transfected cell lines with wild-type and -102A variant human CFTR-directed luciferase reporter genes demonstrates that constructs containing the -102A variant (which creates a Yin Yang 1 (YY1) core element) increases CFTR expression significantly. Electrophoretic mobility shift assays indicate that the -102 site is located in a region of multiple DNA-protein interactions and that the -102A allele recruits specifically an additional nuclear protein related to YY1. The finding that the YY1-binding allele causes a significant increase in CFTR expression in vitro may allow a better understanding of the milder phenotype observed in patients who carry a severe CF mutation within the same gene.

Alleles↗
PubMed2000

Spectrum of CFTR mutations in cystic fibrosis and in congenital absence of the vas deferens in France.

We have collated the results of cystic fibrosis (CF) mutation analysis conducted in 19 laboratories in France. We have analyzed 7, 420 CF alleles, demonstrating a total of 310 different mutations including 24 not reported previously, accounting for 93.56% of CF genes. The most common were F508del (67.18%; range 61-80), G542X (2.86%; range 1-6.7%), N1303K (2.10%; range 0.75-4.6%), and 1717-1G>A (1.31%; range 0-2.8%). Only 11 mutations had relative frequencies >0. 4%, 140 mutations were found on a small number of CF alleles (from 29 to two), and 154 were unique. These data show a clear geographical and/or ethnic variation in the distribution of the most common CF mutations. This spectrum of CF mutations, the largest ever reported in one country, has generated 481 different genotypes. We also investigated a cohort of 800 French men with congenital bilateral absence of the vas deferens (CBAVD) and identified a total of 137 different CFTR mutations. Screening for the most common CF defects in addition to assessment for IVS8-5T allowed us to detect two mutations in 47.63% and one in 24.63% of CBAVD patients. In a subset of 327 CBAVD men who were more extensively investigated through the scanning of coding/flanking sequences, 516 of 654 (78. 90%) alleles were identified, with 15.90% and 70.95% of patients carrying one or two mutations, respectively, and only 13.15% without any detectable CFTR abnormality. The distribution of genotypes, classified according to the expected effect of their mutations on CFTR protein, clearly differed between both populations. CF patients had two severe mutations (87.77%) or one severe and one mild/variable mutation (11.33%), whereas CBAVD men had either a severe and a mild/variable (87.89%) or two mild/variable (11.57%) mutations.

Adult↗
PubMed2000

A new approach for identifying non-pathogenic mutations. An analysis of the cystic fibrosis transmembrane regulator gene in normal individuals.

Given q as the global frequency of the alleles causing a disease, any allele with a frequency higher than q minus the cumulative frequency of the previously known disease-causing mutations (threshold) cannot be the cause of that disease. This principle was applied to the analysis of cystic fibrosis transmembrane conductance regulator (CFTR) mutations in order to decide whether they are the cause of cystic fibrosis. A total of 191 DNA samples from random individuals from Italy, France, and Spain were investigated by DGGE (denaturing gradient gel electrophoresis) analysis of all the coding and proximal non-coding regions of the gene. The mutations detected by DGGE were identified by sequencing. The sample size was sufficient to select essentially all mutations with a frequency of at least 0.01. A total of 46 mutations was detected, 20 of which were missense mutations. Four new mutations were identified: 1341+28 C/T, 2082 C/T, L1096R, and I11131V. Thirteen mutations (125 G/C, 875+40 A/G, TTGAn, IVS8-6 5T, IVS8-6 9T, 1525-61 A/G, M470V, 2694 T/G, 3061-65 C/A, 4002 A/G, 4521 G/A, IVS8 TG10, IVS8 TG12) were classified as non-CF-causing alleles on the basis of their frequency. The remaining mutations have a cumulative frequency far exceeding q; therefore, most of them cannot be CF-causing mutations. This is the first random survey capable of detecting all the polymorphisms of the coding sequence of a gene.

Cystic Fibrosis Transmembrane Conductance Regulato↗
PubMed2000

Meiotic segregation analysis of RB1 alleles in retinoblastoma pedigrees by use of single-sperm typing.

In hereditary retinoblastoma, different epidemiological studies have indicated a preferential paternal transmission of mutant retinoblastoma alleles to offspring, suggesting the occurrence of a meiotic drive. To investigate this mechanism, we analyzed sperm samples from six individuals from five unrelated families affected with hereditary retinoblastoma. Single-sperm typing techniques were performed for each sample by study of two informative short tandem repeats located either in or close to the retinoblastoma gene (RB1). The segregation probability of mutant RB1 alleles in sperm samples was assessed by use of the SPERMSEG program, which includes experimental parameters, recombination fractions between the markers, and segregation parameters. A total of 2,952 single sperm from the six donors were analyzed. We detected a significant segregation distortion in the data as a whole (P=.0099) and a significant heterogeneity in the segregation rate across donors (.0092). Further analysis shows that this result can be explained by segregation distortion in favor of the normal allele in one donor only and that it does not provide evidence of a significant segregation distortion in the other donors. The segregation distortion favoring the mutant RB1 allele does not seem to occur during spermatogenesis, and, thus, meiotic drive may result either from various mechanisms, including a fertilization advantage or a better mobility in sperm bearing a mutant RB1 gene, or from the existence of a defectively imprinted gene located on the human X chromosome.

Adult↗
PubMed2000

BIGH3 exon 14 mutations lead to intermediate type I/IIIA of lattice corneal dystrophies.

PURPOSE: To screen the BIGH3 gene in three unrelated families with lattice corneal dystrophy (LCD), two of which disclosed a particular phenotype. METHODS: Genomic DNA was extracted from peripheral leukocytes of the affected patients and their family members. The entire coding sequence of the BIGH3 gene was screened for mutations by means of transcript analysis on total RNA isolated from peripheral leukocytes by reverse transcription-polymerase chain reaction performed with primers designed for this study. Each mutation was confirmed at the genomic level, by using published primers. RESULTS: One family that had a typical form of LCD, had the described R124C mutation in the BIGH3 gene. Two families with atypical forms of LCD were negative for the previously known mutations of the gene. Direct sequencing of the BIGH3 mRNA in the latter two families allowed us to identify two mutations located in exon 14. They consist of a 9-bp insertion at position 18851886 and one missense mutation at position 1877 of the BIGH3 gene. Three new polymorphisms were also observed. CONCLUSIONS: Two mutations different from those linked to LCD have been found in clinically distinguishable forms of this disease, intermediate between LCDs types I and IIIA. The DNA segment comprising both alterations normally encodes for a highly conserved region of the fourth internal domain of the Betaig-h3 protein, suggesting that this region may be of functional and/or structural importance. The identification of new mutations by screening of the complete BIGH3 gene and the comparative analysis of the induced modifications in betaig-h3 protein should shed light in the understanding of the molecular mechanisms underlying LCDs resulting from mutations in the BIGH3 gene, and may help to explain their phenotypic heterogeneity.

Adult↗
PubMed2000

[Molecular genetics of pigmentary retinopathies: identification of mutations in CHM, RDS, RHO, RPE65, USH2A and XLRS1 genes].

PURPOSE: To evaluate the occurrence and inheritance of various types of pigmentary retinopathy in patients followed at the outpatient clinic in the university hospital, Montpellier, France. To characterize genes and mutations causing these conditions. METHODS: Ophthalmic examination and various visual tests were performed. Mutations were sought from genomic DNA by PCR amplification of exons associated with single-strand conformation analysis and/or direct sequencing. RESULTS: Among 315 patients over an 8-year period, cases of retinitis pigmentosa (63.2%), Usher's syndrome (10.2%), Stargardt's disease (5.4%), choroideremia (3.2%), Leber's congenital amaurosis (3.2%), congenital stationary night blindness (2.9%), cone dystrophy (2.5%), dominant optic atrophy (1.9%), X-linked juvenile retinoschisis (1.6%), Best's disease (1.6%), and others (4.3%) were diagnosed. In retinitis pigmentosa, inheritance could be determined in 54.2% of the cases including dominant autosomic (26.6%), recessive autosomic (22.6%), and X-linked cases (5%) while it could not be confirmed in 45.7% of the cases (simplex cases in the majority). For the 6 examined genes, mutations were found in 22 out of 182 propositus (12.1%). Analysis of phenotype-genotype correlations indicates that in retinitis pigmentosa, RDS is more frequently associated with macular involvement and retinal flecks, RHO with regional disease, and RPE65 with the great severity of the disease with some cases of Leber's congenital amaurosis. CONCLUSIONS: Identification of genes may help in diagnosis and in genetic counseling, especially in simplex cases with retinitis pigmentosa. In this latter condition, molecular diagnosis will be necessary to rationalize future treatments.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Point mutations in the dystrophin gene: evidence for frequent use of cryptic splice sites as a result of splicing defects.

Ten different mutations have been identified in patients with Becker (n = 1) or Duchenne (n = 9) muscular dystrophy using reverse transcription of total RNA, polymerase chain reaction amplification of the whole coding region of the gene and protein truncation test (PTT) analysis. Seven mutations had not been reported previously, and these consist in three nonsense mutations (Q2522X, E2726X, R3381X), three frameshifting deletions (3686-3687delGT, 5126delA, 5759delC), and four splicing defects of which the effects on the muscle dystrophin mRNA transcripts have been analyzed. In one case, a 3' splice-site mutation (IVS74-2A-->G) resulted in a complex pattern of exon skipping involving exons of the C-terminal domain. In the three other cases, nucleotide substitutions in splice donor (IVS26+2T-->A, IVS65+1G-->A) or acceptor (IVS8-15A-->G) recognition sequences led to the use of cryptic splice sites, with consequent insertions of intronic sequences in the processed mRNA. Up to 34% (70/203) of the point mutations reported to date in the dystrophin database (http://www.dmd.nl) affect splice sites of the dystrophin gene. However, altered mRNA splicing has been confirmed experimentally in only 23% of cases (16/70). Combined with PTT, the transcript analysis protocol defined in this study permits direct determination of the impact of intronic variations on the structure of dystrophin mRNA and of the resulting consequences on the translational reading frame. We present evidence for a frequent use of cryptic splice sites as a result of splicing defects.

Base Sequence↗
PubMed1999

No missense mutation in choroideremia patients analyzed to date.

PURPOSE: To elucidate the status of a previously described missense mutation (1442A>T) reported in the Rab Escort Protein 1 gene of a patient with choroideremia. METHODS: The base substitution previously described by Donnelly et al. (Hum Mol Genet 1994;3:1017) was first confirmed by direct genomic DNA sequencing. The REP-1 cDNA region encompassing exons 10-14 was then specifically amplified from lymphocyte-derived mRNA. The effect on mRNA splicing of the mutation was analyzed by RT-PCR and cDNA sequencing. RESULTS: The 1442A>T change located at the penultimate nucleotide of exon 11 causes complete skipping of this exon during the processing of REP-1 mRNA. Loss of exon 11 leads to the translation of a premature termination codon within exon 12. CONCLUSION: RT-PCR analyses demonstrated that the 1442A>T transversion previously described as a possible causative missense mutation does act as a splice-site error and gives rise to a truncated REP-1 protein. The virtual absence of any missense mutation found to be responsible for choroideremia makes the RT-PCR-based protein truncation test the most relevant genotypic diagnostic procedure for identifying mutations in the CHM gene.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Molecular analysis of the rhodopsin gene in southern France: identification of the first duplication responsible for retinitis pigmentosa, c.998999ins4.

PURPOSE: Mutations in the gene encoding rhodopsin, the visual pigment in rod photoreceptors, were shown to be the most common cause of autosomal retinitis pigmentosa (RP). In order to determine the prevalence of rhodopsin alterations in southern French populations, we examined 52 unrelated patients/families with autosomal dominant RP (adRP=29), RP simplex (6), or unclassified RP (17). METHODS: The full coding and flanking sequences of the rhodopsin (RHO) gene were scanned using an improved DGGE (denaturing gradient gel electrophoresis) assay, followed by sequencing of abnormal fragments. RESULTS: This study revealed three RHO mutations in patients with adRP (G106R, R135W, and c.998999ins4) and a number of frequent or rare polymorphisms. No disease-causing sequence variation was found in simplex and unclassified RP pedigrees. Mutation c.998999ins4 has not been previously reported, and appears as the first duplication identified so far in the RHO gene. This frameshift mutation, which is associated with a severe RP, alters the carboxy terminus and predicts a 353-amino acid mutant rhodopsin instead of 348. DISCUSSION: Our study demonstrates that rhodopsin mutations are responsible for only 10.3% of adRP in French populations living in the Mediterranean area in contrast to the 25-35% reported in other populations.

Adult↗
PubMed1999

Complete mutational screening of the cystic fibrosis transmembrane conductance regulator gene: cystic fibrosis mutations are not involved in healthy men with reduced sperm quality.

Based on the analysis of the most frequent mutations responsible for cystic fibrosis (CF), a higher than expected frequency of CF mutations was recently reported in men with infertility due to reduced sperm quality. To further document whether this condition is associated with severe or mild abnormalities of cystic fibrosis transmembrane conductance regulator (CFTR) functions, we carried out a complete scanning of CFTR sequences using a strategy that detects almost all 850 mutations and 150 polymorphisms reported to date in the CFTR gene. We have investigated a cohort of 56 patients with severe oligoasthenoteratozoospermia (OAT) and 50 controls from southern France for CFTR gene mutations and variations. The frequencies of CF-causing mutations and CFTR variations identified in this OAT sample did not differ significantly from the frequencies found in the normal population. However, we observed a 1.7-fold increase in the proportion of homozygotes for a specific CFTR haplotype (TG11-T7-G1540) in the OAT group (P = 0.025). Our results do not confirm a link between CF mutations and reduced sperm quality. Further studies are needed to substantiate the hypothesis that a combination of variants affecting expression and function of the CFTR protein is associated with male infertility.

Base Sequence↗
PubMed1999

[Treatment of early-onset generalized dystonia by chronic bilateral stimulation of the internal globus pallidus. Apropos of a case].

Dystonia musculorum deformans is an inherited severe disease, with a wide clinical polymorphism. The most severe clinical forms with early onset carry a high risk of life-threatening complications. In the absence of any efficient medical treatment, bilateral pallidotomy has previously been reported to be of value in the management of this disease. We report the first clinical case of a severe early-onset generalized dystonia dramatically improved by a bilateral stimulation of the internal globus pallidus. In November 1996, we proposed this neurosurgical procedure for a 8-year-old girl, who had suffered since the age of 3 from severe generalized dystonia, and who progressively became totally dependent and bedridden. She had been under sedation and permanent controlled respiratory assistance for the last two months. The etiology of the disease remained unknown (the DYT1 mutation was absent). Under general anesthesia, we bilaterally implanted a four-contacts electrode in the internal globus pallidus, using the Leksell's stereotactic frame and a 1.5 tesla MRI control. A dramatic improvement was noted 6 weeks later and led us to connect the two electrodes to neurostimulators inserted under the abdominal skin.

Age of Onset↗
PubMed1998

Genetic findings in congenital bilateral aplasia of vas deferens patients and identification of six novel mutatations. Mutations in brief no. 138. Online.

Congential bilateral aplasia of vas deferens (CBAVD), a form of male sterility, has been suggested to represent a "genital" form of cystic fibrosis (CF), as mutations in the CFTR gene have been identified in most patients with this condition. Interestingly, the 5T allele in intron 8 appeared to be the most frequent mutation associated with CBAVD. However, the molecular basis of CBAVD is not completely understood. We have analysed the complete coding and flanking CFTR sequences by PCR-DGGE in 64 men with CBAVD from southern France with the aim to list any sequence alteration. Fourty-two of the 64 patients (65.6%) had mutations on both copies of the CFTR gene, including one patient with two mutations in the same copy (DF508 + A1067T). The 5T allele was present in 21/64 cases (33%). Six of the 28 different mutations identified in this study had never been described previously, and appeared to be specific to CBAVD (P111L, M244K, A1364V, G544V, 2896insAG,-33G->A).

Cystic Fibrosis Transmembrane Conductance Regulato↗