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Biomedical subjects

L Messiaen

Publications and source records attributed to L Messiaen.

At least 19 recordsLinked to original sources
PubMed2006

An absence of cutaneous neurofibromas associated with a 3-bp inframe deletion in exon 17 of the NF1 gene (c.2970-2972 delAAT): evidence of a clinically significant NF1 genotype-phenotype correlation.

Neurofibromatosis type 1 (NF1) is characterized by cafe-au-lait spots, skinfold freckling, and cutaneous neurofibromas. No obvious relationships between small mutations (<20 bp) of the NF1 gene and a specific phenotype have previously been demonstrated, which suggests that interaction with either unlinked modifying genes and/or the normal NF1 allele may be involved in the development of the particular clinical features associated with NF1. We identified 21 unrelated probands with NF1 (14 familial and 7 sporadic cases) who were all found to have the same c.2970-2972 delAAT (p.990delM) mutation but no cutaneous neurofibromas or clinically obvious plexiform neurofibromas. Molecular analysis identified the same 3-bp inframe deletion (c.2970-2972 delAAT) in exon 17 of the NF1 gene in all affected subjects. The Delta AAT mutation is predicted to result in the loss of one of two adjacent methionines (codon 991 or 992) ( Delta Met991), in conjunction with silent ACA-->ACG change of codon 990. These two methionine residues are located in a highly conserved region of neurofibromin and are expected, therefore, to have a functional role in the protein. Our data represent results from the first study to correlate a specific small mutation of the NF1 gene to the expression of a particular clinical phenotype. The biological mechanism that relates this specific mutation to the suppression of cutaneous neurofibroma development is unknown.

Adolescent↗
PubMed2006

Spectrum of single- and multiexon NF1 copy number changes in a cohort of 1,100 unselected NF1 patients.

Neurofibromatosis type 1 (NF1), the most common tumor-predisposing disorder in humans, is caused by defects in the NF1 tumor-suppressor gene. Comprehensive mutation analysis applying RNA-based techniques complemented with FISH analysis achieves mutation detection rates of approximately 95% in NF1 patients. The majority of mutations are minor lesions, and approximately 5% are total gene deletions. We found 13 single- and/or multiexon deletions/duplications out of 1,050 detected mutations using our RNA-based approach in a cohort of 1,100 NF1 patients and confirmed these changes using multiplex ligation-dependent probe amplification (MLPA). With MLPA, we found another 12 novel multiexon deletion/duplications in 55 NF1 patients for whom analysis with multiple assays had not revealed a NF1 mutation, including 50 previously analyzed comprehensively. The extent of the 22 deletions and 3 duplications varied greatly, and there was no clustering of breakpoints. We also evaluated the sensitivity of MLPA in identifying deletions in a mosaic state. Furthermore, we tested whether the MLPA P122 NF1 area assay could distinguish between type I deletions, with breakpoints in low-copy repeats (NF1-LCRs), and type II deletions, caused by aberrant recombination between the JJAZ gene and its pseudogene. Our study showed that intragenic deletions and/or duplications represent only approximately 2% of all NF1 mutations. Although MLPA did not substantially increase the mutation detection rate in NF1 patients, it was a useful first step in a comprehensive mutation analysis scheme to quickly pinpoint patients with single- or multiexon deletions/duplications as well as patients with a total gene deletion who will not need full sequencing of the complete coding region.

Exons↗
PubMed2005

Identification of novel deletion breakpoints bordered by segmental duplications in the NF1 locus using high resolution array-CGH.

BACKGROUND: Segmental duplications flanking the neurofibromatosis type 1 (NF1) gene locus on 17q11 mediate most gene deletions in NF1 patients. However, the large size of the gene and the complexity of the locus architecture pose difficulties in deletion analysis. We report the construction and application of the first NF1 locus specific microarray, covering 2.24 Mb of 17q11, using a non-redundant approach for array design. The average resolution of analysis for the array is approximately 12 kb per measurement point with an increased average resolution of 6.4 kb for the NF1 gene. METHODS: We performed a comprehensive array-CGH analysis of 161 NF1 derived samples and identified heterozygous deletions of various sizes in 39 cases. The typical deletion was identified in 26 cases, whereas 13 samples showed atypical deletion profiles. RESULTS: The size of the atypical deletions, contained within the segment covered by the array, ranged from 6 kb to 1.6 Mb and their breakpoints could be accurately determined. Moreover, 10 atypical deletions were observed to share a common breakpoint either on the proximal or distal end of the deletion. The deletions identified by array-CGH were independently confirmed using multiplex ligation-dependent probe amplification. Bioinformatic analysis of the entire locus identified 33 segmental duplications. CONCLUSIONS: We show that at least one of these segmental duplications, which borders the proximal breakpoint located within the NF1 intron 1 in five atypical deletions, might represent a novel hot spot for deletions. Our array constitutes a novel and reliable tool offering significantly improved diagnostics for this common disorder.

Chromosome Breakage↗
PubMed2004

BRCA1 and BRCA2 germline mutation spectrum and frequencies in Belgian breast/ovarian cancer families.

Worldwide variation in the distribution of BRCA1 and BRCA2 mutations is well recognised, and for the Belgian population no comprehensive studies about BRCA1/2 mutation spectra or frequencies have been published. We screened the complete coding region of both genes in 451 individuals from 349 Belgian families referred to a family cancer clinic and identified 49 families with a BRCA1 and 26 families with a BRCA2 mutation. Six major recurrent mutations (BRCA1 IVS5+3A>G, 2478-2479insG, E1221X and BRCA2 IVS6+1G>A, 6503-6504delTT, 9132delC) accounted for nearly 60% of all mutations identified. Besides 75 true pathogenic mutations, we identified several variants of unknown clinical significance. In combination with a family history, an early average age of female breast cancer diagnosis (P<0.001), and the presence of a relative with ovarian cancer (P<0.0001) or multiple primary breast cancers (P=0.002), increased the chance for finding a mutation. Male breast cancer was indicative of a BRCA2 mutation segregating in the family (P=0.002). Mutations in the 5'-end of BRCA1 and BRCA2 were associated with a significantly increased risk for ovarian cancer relative to the central portion of the gene. Our study suggests a role for additional breast cancer susceptibility genes in the Belgian population, since mutation detection ratios were low in high-risk breast cancer-only families as compared to breast-ovarian cancer families. Given the large proportion of recurring mutations, molecular testing can now be organised in a more cost-effective way. Our data allow optimisation of genetic counselling and disease prevention in Belgian breast/ovarian cancer families.

Adult↗
PubMed2004

A new type of autosomal recessive spondyloepiphyseal dysplasia tarda.

Repeated occurrence of a hitherto unrecognized form of spondyloepiphyseal dysplasia tarda (SED tarda) has been studied in two independent families. Because parental consanguinity was also present in one family, autosomal recessive inheritance is proposed. The onset was in late childhood. The slowly evolving disorder shared several features of the already known types of SED tarda. The radiographic abnormalities were limited to the spine and proximal femora. The patients' hands were normal. The entity described is set apart not only from the X-linked and autosomal-dominant forms of SED tarda but also from the already delineated autosomal recessive types by significant clinical and radiographic differences. Final genotypic characterization must await the results of genetic linkage studies and of appropriate molecular genetics investigations.

Adolescent↗
PubMed2002

Chromosomal radiosensitivity in breast cancer patients with a known or putative genetic predisposition.

The chromosomal radiosensitivity of breast cancer patients with a known or putative genetic predisposition was investigated and compared to a group of healthy women. The chromosomal radiosensitivity was assessed with the G2 and the G0-micronucleus assay. For the G2 assay lymphocytes were irradiated in vitro with a dose of 0.4 Gy (60)Co gamma-rays after 71 h incubation, and chromatid breaks were scored in 50 metaphases. For the micronucleus assay lymphocytes were exposed in vitro to 3.5 Gy (60)Co gamma-rays at a high dose rate or low dose rate. 70 h post-irradiation cultures were arrested and micronuclei were scored in 1000 binucleate cells. The results demonstrated that the group of breast cancer patients with a known or putative genetic predisposition was on the average more radiosensitive than a population of healthy women, and this with the G2 as well as with the high dose rate and low dose rate micronucleus assay. With the G2 assay 43% of the patients were found to be radiosensitive. A higher proportion of the patients were radiosensitive with the micronucleus assay (45% with high dose rate and 61% with low dose rate). No correlation was found between the G2 and the G0-micronucleus chromosomal radiosensitivity. Out of the different subgroups considered, the group of the young breast cancer patients without family history showed the highest percentage of radiosensitive cases in the G2 (50%) as well as in the micronucleus assay (75-78%).

Adult↗
PubMed2002

Does monosymptomatic enuresis exist? A molecular genetic exploration of 32 families with enuresis/incontinence.

OBJECTIVE: s To confirm linkage to microsatellite markers on chromosome 8q, 12q, 13q and 22q in families with nocturnal enuresis/incontinence segregating with an autosomal dominant pattern, and to determine if there is an association between the clinical subtype and these linked loci. PATIENTS AND METHODS: Families with at least three members with nocturnal enuresis in two generations were included in the study. The index patient was > or = 7 years old and had evidence of bladder dysfunction; all other family members were > or = 5 years old. Bladder dysfunction in the index patients was documented by video-urodynamics when indicated. A nycthemeral rhythm of diuresis was documented in all index patients. The clinical diagnosis of all family members was based on a questionnaire on voiding problems and micturition habits, uroflowmetry, measurement of functional bladder capacity and nocturnal diuresis. Linkage was analysed using an autosomal dominant model with a gene frequency equal to 0.05 and a penetrance of 0.9. RESULTS: Thirty-two families with nocturnal enuresis/incontinence (one with four, 25 with three and six with two generations) were included. The mean number of persons included per family was 10 and on average five members were symptomatic. Linkage of nocturnal enuresis to a region on chromosome 22q11 was found in nine families, to 13q13-14 in six and to 12q in four. There was no convincing evidence for linkage to chromosome 8q. Clinical findings in the proband and their family members with possible linkage to a given locus were heterogeneous, and hence no clear genotype/phenotype correlation could be postulated. CONCLUSION: These findings support the hypothesis of the genetic and phenotypic heterogeneity of nocturnal enuresis/incontinence. Putative linkage was confirmed to the same chromosomal loci as in previous studies of 'monosymptomatic' enuresis and different phenotypes were linked to the same loci.

Adolescent↗
PubMed2002

Strategies for prenatal and preimplantation genetic diagnosis in Marfan syndrome (MFS).

Marfan syndrome (MFS) is an autosomal dominant disorder with a prevalence of 2-3 per 10 000 individuals. Symptoms range from skeletal overgrowth, cutaneous striae to ectopia lentis and aortic dilatation leading to dissection. Prenatal diagnosis was until recently mainly performed in familial cases by linkage analysis. However, mutation detection has become available with thorough screening methods. The phenotypic variability observed in MFS makes reproductive options difficult, as molecular diagnosis cannot predict clinical severity of the disease. Data are presented on 15 prenatal and/or preimplantation genetic diagnoses (PGD) in nine families, originating from Belgium, the Netherlands, Spain and France. In four families data from linkage analysis were used, whereas in five other families the causative FBN1 mutation was characterised. Four PGD cycles in two couples led to one ongoing pregnancy. In addition, two amniocenteses and nine chorionic villus (CV) samplings were performed. In five pregnancies an affected fetus was diagnosed. In one of them, the couple chose to continue the pregnancy and an affected child was born, whereas the other four couples decided to terminate the pregnancy. It is expected that the greater availability of mutation testing of the FBN1 gene will increase requests for prenatal diagnosis. PGD appears to be an acceptable alternative for couples facing ethical reproductive dilemmas.

Adult↗
PubMed2001

Spectrum of FOXL2 gene mutations in blepharophimosis-ptosis-epicanthus inversus (BPES) families demonstrates a genotype--phenotype correlation.

Mutations in FOXL2, a forkhead transcription factor gene, have recently been shown to cause blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) types I and II, a rare genetic disorder. In BPES type I a complex eyelid malformation is associated with premature ovarian failure (POF), whereas in BPES type II the eyelid defect occurs as an isolated entity. In this study, we describe the identification of novel mutations in the FOXL2 gene in BPES types I and II families, in sporadic BPES patients, and in BPES families where the type could not be established. In 67% of the patients studied, we identified a mutation in the FOXL2 gene. In total, 21 mutations (17 of which are novel) and one microdeletion were identified. Thirteen of these FOXL2 mutations are unique. In this study, we demonstrate that there is a genotype--phenotype correlation for either types of BPES by the finding that mutations predicted to result in a truncated protein either lacking or containing the forkhead domain lead to BPES type I. In contrast, duplications within or downstream of the forkhead domain, and a frameshift downstream of them, all predicted to result in an extended protein, cause BPES type II. In addition, in 30 unrelated patients with isolated POF no causal mutations were identified in FOXL2. Our study provides further evidence that FOXL2 haploinsufficiency may cause BPES types I and II by the effect of a null allele and a hypomorphic allele, respectively. Furthermore, we propose that in a fraction of the BPES patients the genetic defect does not reside within the coding region of the FOXL2 gene and may be caused by a position effect.

Alleles↗
PubMed2001

Quantification of splice variants using real-time PCR.

A reliable and robust method for measuring the expression of alternatively spliced transcripts is an important step in investigating the significance of each variant. So far, accurate quantification of splice variants has been laborious and difficult due to the intrinsic limitations of conventional methods. The many advantages of real-time PCR have made this technique attractive to study its application in quantification of splice isoforms. We use skipping of exon 37 in the NF1 gene as a model to compare and evaluate the different strategies for quantitating splice variants using real-time PCR. An overview of three different possibilities for detecting alternative transcripts is given. We propose the use of a boundary-spanning primer to quantify isoforms that differ greatly in abundance. We describe here a novel method for creating a reliable standard curve using one plasmid containing both alternative transcripts. In addition, we validate the use of an absolute standard curve based on a dilution series of fluorometrically quantified PCR products.

Alternative Splicing↗
PubMed2001

Diverse prevalence of large deletions within the OA1 gene in ocular albinism type 1 patients from Europe and North America.

Ocular albinism type 1 (OA1) is an X-linked disorder mainly characterized by congenital nystagmus and photodysphoria, moderate to severe reduction of visual acuity, hypopigmentation of the retina, and the presence of macromelanosomes in the skin and eyes. We have previously isolated the gene for OA1 and characterized its protein product as melanosomal membrane glycoprotein displaying structural and functional features of G protein-coupled receptors. We and others have identified mutations of various types within the OA1 gene in patients with this disorder, including deletions and splice site, frameshift, nonsense, and missense mutations. However, different prevalences of large intragenic deletions have been reported, ranging from 10% to 50% in independent studies. To determine whether these differences might be related to the geographic origin of the OA1 families tested, we performed a further extensive mutation analysis study leading to the identification of pathogenic mutations in 30 unrelated OA1 patients mainly from Europe and North America. These results, together with our earlier mutation reports on OA1, allow us to resolve the apparent discrepancies between previous studies and point to a substantial difference in the frequency of large intragenic deletions in European (<10%) compared with North American (>50%) OA1 families. These observations and our overall refinement of point mutation distribution within the OA1 gene have important implications for the molecular diagnosis of OA1 and for the establishment of any mutation detection program for this disorder.

Albinism, Ocular↗
PubMed2001

Cloning and characterization of human WDR10, a novel gene located at 3q21 encoding a WD-repeat protein that is highly expressed in pituitary and testis.

Members of the steroid-thyroid-retinoid receptor superfamily regulate a spectrum of cellular functions, including metabolism and growth and differentiation. We sought to isolate novel members of this family by using degenerate oligonucleotide primers directed to sequences encoding the AF-2 domain of these molecules in a PCR-based approach. The AF-2 domain serves a critical function in recruiting coregulatory molecules and in transcriptional activation. We report the cloning and initial characterization of a novel gene, WDR10, which encodes a 140-kD protein that is highly expressed in pituitary and testis. This protein, WDR10p, contains an AF-2 domain as well as seven N-terminal WD repeats and is highly conserved through evolution. Chromosomal localization studies placed WDR10 at 3q21, near a locus for the Moebius syndrome, Hailey-Hailey disease, and rhodopsin, which is involved in several forms of retinitis pigmentosa. The expression pattern of WDR10 and its chromosomal location makes this novel gene a candidate gene for the hypogonadism associated with some forms of retinitis pigmentosa and the Moebius syndrome.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Carrier screening for cystic fibrosis in a prenatal setting.

Maternal prenatal cystic fibrosis (CF) screening was offered from September, 1997, to April, 1999, at the Ghent University Hospital, to couples undergoing prenatal diagnosis (amniocentesis) for reasons not related to CF. Fifteen minutes were devoted to explaining CF, CF screening, and the study protocol. The purpose was to assess the short- and long-term knowledge of CF, the attitude towards carrier screening, and carriership. A total of 314 couples entered the pilot study; 13 female CF carriers were identified. None of their partners carried an identifiable mutation. Our survey results show that information about CF and CF screening can be given effectively as part of antenatal care because most couples recalled important medical and genetic issues, valued the genetic test for CF, and seemed to cope well with the results. Risk estimates and actual numbers were more difficult to process and recall. From the small number of couples in which the woman alone was found to be a carrier, there was little or no evidence of marked distress.

Adolescent↗
PubMed2001

Association between Cys282Tyr missense mutation and haptoglobin phenotype polymorphism in patients with chronic hepatitis C.

INTRODUCTION: In patients with chronic hepatitis C infection, the haptoglobin (Hp) 1-1 phenotype is overrepresented. Data regarding the occurrence of the Cys282Tyr missense mutation in these patients are less clear. We studied the prevalence of both variables in a cohort of patients with chronic hepatitis C and looked for interaction between the two variables. MATERIALS AND METHODS: The study group consisted of 142 patients chronically infected with the hepatitis C virus. All patients were examined for the occurrence of the Cys282Tyr missense mutation, and in 132 of them the Hp phenotype was determined. The Cys282Tyr missense mutation was detected by restriction fragment length polymorphism (RFLP) using a standard polymerase chain reaction (PCR) technique and RsaI digestion. Hp phenotypes were determined using starch gel electrophoresis of haemoglobin-supplemented serum followed by peroxidase staining. RESULTS: A significant overrepresentation of the Hp 1-1 phenotype was found (36/132, 27%, P < 0.01 v. control population). This overrepresentation was observed only in the patients homozygous for the wild-type allele of the HFE gene. The Cys282Tyr allele was significantly overrepresented in hepatitis C patients (0.12 v. 0.07, P < 0.05) and principally in patients with the Hp 2-1 and 2-2 phenotypes. CONCLUSION: In patients with chronic hepatitis C infection, both the Hp 1-1 and the Cys282Tyr allele occur more frequently than in a control population. Remarkably, these genes seem to determine each other's occurrence, such that the overrepresentation of the Hp 1-1 phenotype is seen only in Cys282Tyr-negative subjects, while the overrepresentation of the Cys282Tyr allele is observed in Hp 1-1-negative subjects. Differences in immunomodulating and in oxidative stress-inducing capacities between the two genes may explain this finding.

Adult↗
PubMed2000

A high occurrence of BRCA1 and BRCA2 mutations among Czech hereditary breast and breast-ovarian cancer families.

BACKGROUND: About 5-10% of breast and ovarian cancer can be of hereditary origin. Germline mutations in BRCA1 or BRCA2 and probably other yet unknown genes may cause predisposition to these cancers. METHODS AND RESULTS: Molecular genetic testing of BRCA1 and BRCA2 genes in 21 high-risk breast and breast/ovarian cancer families was performed in order to find the types and the frequency of mutations in the South Moravian region of the Czech Republic. A germline mutation was found in 12 of 21 tested families (57%), 9 mutations in BRCA1 gene and 3 mutations in BRCA2 gene. In 4 unrelated families the same germline mutation in the BRCA1 gene (5382insC) was identified. In 12 families diagnosed with breast cancer only syndrome 3 families harbouring BRCA1 mutations and 3 families harbouring BRCA2 mutations were found. In 9 families with breast-ovarian cancer syndrome 6 families carrying BRCA1 mutations were detected. CONCLUSION: Molecular genetic testing of BRCA1 and BRCA2 genes in high-risk women with breast/ovarian cancer is effective in determining genetic predisposition to cancer. Spectrum of mutations found in both genes is variable and further investigation is needed for estimation of more frequent or "founder" mutations. The genetic counselling and preventive clinical follow-up of gene carriers has to be part of the genetic program.

Adult↗