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T Bienvenu

Publications and source records attributed to T Bienvenu.

At least 19 recordsLinked to original sources
PubMed2006

A new large CFTR rearrangement illustrates the importance of searching for complex alleles.

The p.Val754Met variant, described in 1996 in a CF patient, has been considered a CF mutation. However, biochemical aspects, results of functional studies and, finally, the identification of a complex deletion removing exons 3 to 10 and 14b to 16 in cis of p.Val754Met in a CF patient, argue against a strong deleterious effect. An inventory through the French CF network of patients carrying p.Val754Met led to the registration of seven patients (CF: n=4; idiopathic chronic pancreatitis: n=3) and six healthy individuals, all heterozygous for the variation. Extensive CFTR gene analysis was carried out, including the search for large rearrangements and other possible mutations. The complex deletion, whose breakpoints are described here, was found only in the four CF patients, in association with the same haplotype. This data, added to the fact that the p.[Phe508del]+[Val754Met] genotype was found in a healthy individual, bring further arguments against the association of p.Val754Met with CF. We thus suggest looking for a possible complex allele whenever p.Val754Met is detected and considering it neutral regarding genetic counseling when found in isolation.

Adolescent↗
PubMed2006

Maternal origin of a novel C-terminal truncation mutation in CDKL5 causing a severe atypical form of Rett syndrome.

The CDKL5 gene has been implicated in infantile spasms and more recently in a Rett syndrome-like phenotype. We report a case of a young girl presenting generalized convulsions at 10 days of life. Subsequent mutation analysis by denaturing high-performance liquid chromatography of MECP2 and CDKL5 genes revealed heterozygosity for a c.47_48insAGG insertion in exon 1 of MECP2 and heterozygosity for a new nonsense mutation p.Q834X and a new missense variant p.V999M in the CDKL5 gene. Co-segregation analysis showed that the nonsense mutation was a de novo mutation and that the insertion and the missense variant were also found in the asymptomatic mother. In the absence of skewed X inactivation in the mother, it is likely that these last two variants are not pathogenic. Reverse transcription-polymerase chain reaction from lymphoblastoid cells of the patient showed only the transcript without the nonsense and missense variations suggesting decreased stability of mature mRNA by nonsense-mediated decay. These data also suggest an occurrence of the de novo mutation in maternal germ line cells. Moreover, this report reinforces the observation that the CDKL5 phenotype overlaps with Rett syndrome and that CDKL5 gene analysis is recommended in females with a seizure disorder commencing in the first weeks of life.

Base Sequence↗
PubMed2005

Maternal mosaicism for mutations in the ARX gene in a family with X linked mental retardation.

We describe two brothers with mental retardation (MR) due to a c.428_451dup24 in the ARX gene. The mother did not apparently carry the mutation, as determined by dHPLC and by fragment size analysis. Using semiquantitative fluorescent PCR, we show however that 4% of her lymphocytes and 24% of her fibroblasts harbored the duplication. We thus show that the mother displays somatic mosaicism for the duplication thereby highlighting the need to reconsider the molecular screening in sporadic cases of MR.

Amino Acid Sequence↗
PubMed2005

Screening of ARX in mental retardation families: Consequences for the strategy of molecular diagnosis.

Mutations in the human ARX gene have been shown to cause nonsyndromic X-linked mental retardation (MRX) as well as syndromic forms such as X-linked lissencephaly with abnormal genitalia (XLAG), Partington syndrome and X-linked infantile spasm. The most common causative mutation, a duplication of 24 bp, was found in families with a variety of phenotypes, but not in the more severe XLAG phenotypes. The aim of the study was to access the frequency of ARX mutations in families with established or putative X-linked mental retardation (XLMR) collected by the European XLMR Consortium. We screened the entire coding region of ARX for mutations in 197 novel XLMR families by denaturing high-performance liquid chromatography, and we identified eight mutations (six c.428_451dup24, one insertion and one novel missense mutation p.P38S). To better define the prevalence of ARX mutations, we included previously reported results of 157 XLMR families. Together, these data showed the relatively high rate (9.5%) of ARX mutations in X-linked MR families and an expectedly low rate in families with affected brother pairs (2.2%). This study confirms that the frequency of ARX mutations is high in XLMR, and the analysis of ARX in MRX should not be limited to duplication.

Amino Acid Sequence↗
PubMed2005

Reduced exhaled NO is related to impaired nasal potential difference in patients with cystic fibrosis.

Nitric oxide (NO) plays a central role in many airway physiological functions, and its production appears to be related with progression of lung disease in patients with cystic fibrosis (CF). However, underlying mechanisms which specifically link NO and CF-related lung disease remain unclear. Following in vitro and animal studies suggesting a role for NO in ion transport in various epithelia, this work investigates the relationship between transepithelial baseline potential difference (BPD), an index of airway ion transport, and exhaled NO in the airways of adult patients with CF. Association with other phenotypic traits, lung function tests and CFTR genotype was also assessed. Using simple linear regression, F(E)NO and transepithelial BPD values were significantly inversely correlated (p<0.001, r=-0.53). Polynomial analysis evidenced an asymptotic relationship between F(E)NO and BPD values, yielding a plateau for absolute BPD values above 50 mV. This relation was not altered by adjustment for clinical and genetic characteristics of the patients. The relationship between exhaled NO and transepithelial BPD suggests that low NO concentrations likely worsens airway ion transport impairment resulting from CFTR defect. These results fit with experimental studies that suggest the inhibitory effect of NO on sodium absorption, which is the main determinant of airway basal transepithelial conductance.

Adult↗
PubMed2005

Is the CAG repeat of mitochondrial DNA polymerase gamma (POLG) associated with male infertility? A multi-centre French study.

BACKGROUND: Recent data emphasized the implication of polymerase gamma (POLG) CAG repeats in infertility, making it a very attractive gene for study. A comparison of POLG CAG repeats in infertile and fertile men showed a clear association between the absence of the usual 10-CAG allele and male infertility, excluding azoospermia. It has also been suggested that the POLG gene polymorphism should be considered as a possible contributing factor in unexplained couple infertility where semen parameters are normal. In this study, we investigated the POLG CAG repeats, in a well-defined population of patients with severe male factor infertility. METHODS: We conducted a large study of POLG CAG repeats in 433 infertile and 91 fertile, normozoospermic and healthy males. In all subjects, phenotypic data, including semen parameters, hormonal status and clinical profiles, were available. RESULTS: Thirteen 'homozygous mutants' (3%) were found among the 433 idiopathic infertile patients. The follow-up of the 13 'homozygous mutant' resulted in pregnancy for more than half of the couples, through assisted reproductive techniques or even spontaneously. In addition, one 'homozygous mutant' was identified in 91 fertile men (1.1%) CONCLUSION: Under our conditions, our study does not confirm any relationship between the polymorphic CAG repeat in the POLG gene and male infertility.

Adult↗
PubMed2005

Malnutrition in adults with cystic fibrosis.

OBJECTIVE: To determine the prevalence and clinical features of malnutrition and its relationship with the CFTR genotype in a cystic fibrosis (CF) adult population. DESIGN: Cross-sectional study. SETTING: Department of Pulmonology, Cochin Hospital, Paris, France. SUBJECTS: 163 CF adults seen between 1997 and 1999. RESULTS: Mean age was 28.8 y. Mean body mass index (BMI) was 19.1 kg/m2. Malnutrition (BMI<18.5 kg/m2) was seen in 81 patients (49.7%). Its severity was associated with diagnosis of CF before the age of 18 y (P<0.01), FEV1 values below 30% (P<0.01), the yearly decline of FEV1 (P<0.01), pancreatic insufficiency (P<0.01) and gastro-oesophageal reflux (P<0.01). Malnutrition was observed in 58.7% of patients with a severe CFTR genotype but in 28.6% of patients with a mild genotype (P<0.001). CONCLUSION: Malnutrition remains frequent in adults with CF except in patients presenting with a mild CFTR genotype (leading to a mild phenotype and to later diagnosis).

Adult↗
PubMed2005

Spectrum of CFTR mutations on Réunion Island: impact on neonatal screening.

The large heterogeneity in the cystic fibrosis (CF) gene is the main difficulty for genotype characterization. Numerous studies have reported considerable variations in frequencies of CF transmembrane conductance regulator (CFTR) mutations in different populations, such as African, Asian, or European populations. To completely characterize the spectrum of mutations in the CFTR gene in the Réunion Island population, we screened 228 CF chromosomes using denaturing high-pressure liquid chromatography and denaturing gradient gel electrophoresis following by direct sequencing. We identified 27 mutations, accounting for 93% of CF chromosomes. They included three novel mutations (M1T, 3121-3C-->G, and L1324P), which are described in this paper. The detection of such a high proportion of Réunion Island CFTR mutations is important for improving neonatal screening of CF on Réunion Island.

Cystic Fibrosis↗
PubMed2004

Nasal airway ion transport is linked to the cystic fibrosis phenotype in adult patients.

BACKGROUND: This study was conducted to determine whether the major nasal airway ion transport abnormalities in cystic fibrosis (that is, defective cAMP regulated chloride secretion and basal sodium hyperabsorption) are related to the clinical expression of cystic fibrosis and/or to the genotype. METHODS: Nasal potential difference was measured in 79 adult patients with cystic fibrosis for whom clinical status, respiratory function, and CFTR genotype were determined. RESULTS: In univariate and multivariate analysis, patients with pancreatic insufficiency were more likely to have low responses to low chloride (odds ratio (OR) 8.6 (95% CI 1.3 to 58.5), p = 0.03) and isoproterenol (OR 11.2 (95% CI 1.3 to 93.9), p = 0.03) solutions. Similarly, in univariate and multivariate analysis, patients with poor respiratory function (forced expiratory volume in 1 second <50% of predicted value) were more likely to have an enhanced response to amiloride solution (OR 3.7 (95% CI 1.3 to 11.0), p = 0.02). However, there was no significant relationship between nasal potential difference and the severity of the genotype. CONCLUSIONS: Nasal epithelial ion transport in cystic fibrosis is linked to the clinical expression of the disease. The pancreatic status appears to be mostly related to the defect in epithelial chloride secretion whereas the respiratory status is mostly related to abnormal sodium transport and the regulatory function of the CFTR protein.

Adult↗
PubMed2003

[Cystic fibrosis: relationship between genotype and phenotype].

Cystic fibrosis (CF) is one of the most common lethal autosomal recessive disease among the Caucasian population. It is caused by defects in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. More than 1000 different CF mutations have been described. This large heterogeneity of mutations could explain in part the great variability of clinical expression of the disease. However, the severity of the lung disease is very different among patients with similar CFTR genotype, even from the same family. These discrepancies in phenotypes within patients of the same genotype suggest the influence of nongenetic environmental factors and genetic modifiers outside the CF locus.

Cystic Fibrosis↗
PubMed2003

[Indications and modalities of assisted reproductive techniques in infertile women with cystic fibrosis].

OBJECTIVE: To treat cystic fibrosis women who failed to conceive. PATIENTS AND METHODS: Multidisciplinary coordinated approach in 20 infertile women affected with cystic fibrosis. Advisability of pregnancy was based on the assessment of pulmonary and nutritional status, risks of maternal health deterioration, infertility factors, risk of cystic fibrosis in the offspring. Assisted reproductive techniques in moderately affected women are described. RESULTS: Three patients requested only information, three were discouraged, two are still evaluated, 12 were treated and three delivered healthy children. The pulmonary status of each patient remained unchanged 36 months after delivery, and all three children remain healthy. DISCUSSION AND CONCLUSION: Assisted reproductive techniques are an option in moderately affected infertile cystic fibrosis women. Advisability and management of pregnancy should be provided by a coordinated team of healthcare professionals with knowledge and experience in cystic fibrosis.

Adult↗
PubMed2003

DHPLC-based method for DNA methylation analysis of differential methylated regions from imprinted genes.

The bisulfite genomic sequencing method is one of the most widely used techniques for methylation analysis in heterogeneous unbiased PCR, amplifying for both methylated and unmethylated alleles simultaneously. However, it requires labor-intensive and time-consuming cloning and sequencing steps. In the current study, we used a denaturing high-performance liquid chromatography (DHPLC) procedure in a complementary way with the bisulfite genomic sequencing to analyze the methylation of differentially methylated regions (DMRs) of imprinted genes. We showed reliable and reproducible results in distinguishing overall methylation profiles of DMRs regions of human SNRPN, H19, MEST/PEG1, LIT1, IGF2, TSSC5, WT1 antisense, and mouse H19, Mest/Peg1, Igf2R imprinted genes. These DHPLC profiles were in accordance with bisulfite genomic sequencing data and may serve as a type of "fingerprint," revealing the overall methylation status of DMRs associated with sample heterogeneity. We conclude that DHPLC analysis could be used to increase the throughput efficiency of methylation pattern analysis of imprinted genes after the bisulfite conversion of genomic DNA and unbiased PCR amplification.

Animals↗
PubMed2001

MECP2 is highly mutated in X-linked mental retardation.

Following the recent discovery that the methyl-CpG binding protein 2 (MECP2) gene located on Xq28 is involved in Rett syndrome (RTT), a wild spectrum of phenotypes, including mental handicap, has been shown to be associated with mutations in MECP2. These findings, with the compelling genetic evidence suggesting the presence in Xq28 of additional genes besides RabGDI1 and FMR2 involved in non-specific X-linked mental retardation (MRX), prompted us to investigate MECP2 in MRX families. Two novel mutations, not found in RTT, were identified. The first mutation, an E137G, was identified in the MRX16 family, and the second, R167W, was identified in a new mental retardation (MR) family shown to be linked to Xq28. In view of these data, we screened MECP2 in a cohort of 185 patients found negative for the expansions across the FRAXA CGG repeat and reported the identification of mutations in four sporadic cases of MR. One of the mutations, A140V, which we found in two patients, has been described previously, whereas the two others, P399L and R453Q, are novel mutations. In addition to the results demonstrating the involvement of MECP2 in MRX, this study shows that the frequency of mutations in MECP2 in the mentally retarded population screened for the fragile X syndrome is comparable to the frequency of the CGG expansions in FMR1. Therefore, implementation of systematic screening of MECP2 in MR patients should result in significant progress in the field of molecular diagnosis and genetic counseling of mental handicap.

Adult↗
PubMed2001

Five novel frameshift mutations in exon 3 and 4 of the MECP2 gene identified in Rett patients: Consequences for the molecular diagnosis strategy.

Rett syndrome (RTT) is a severe progressive neurological disorder that affects almost exclusively females. The gene responsible for this disorder, MECP2, was recently identified by candidate gene strategy. Mutations were detected in 70-85% of RTT cases. We report here five novel frameshift mutations (named 345delC, 895del202, 989ins18del8, 996insAG and 1124del53) in exon 3 and 4 of the MECP2 gene. To avoid the missing of few small deletions in RTT patients using classical mutation screening approaches, we suggest that screening of the mutations in the MECP2 gene in RTT girls should include at least a large PCR to amplify exon 4 entirely.

Chromosomal Proteins, Non-Histone↗