Recurrent insertional polydactyly and situs inversus in a Bardet-Biedl syndrome family.
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Bardet-Biedl Syndrome↗
Biomedical subjects
Michel Goossens
Publications and source records attributed to Michel Goossens.
ZFHX1B mutations in patients with Mowat-Wilson syndrome.
Mowat-Wilson syndrome (MWS) is a recently delineated mental retardation (MR)-multiple congenital anomaly syndrome, characterized by typical facies, severe MR, epilepsy, and variable congenital malformations, including Hirschsprung disease (HSCR), genital anomalies, congenital heart disease (CHD), and agenesis of the corpus callosum (ACC). It is caused by de novo heterozygous mutations or deletions of the ZFHX1B gene located at 2q22. ZFHX1B encodes Smad-interacting protein-1 (SMADIP1 or SIP1), a transcriptional corepressor involved in the transforming growth factor-beta signaling pathway. It is a highly evolutionarily conserved gene, widely expressed in embryological development. Over 100 mutations have been described in patients with clinically typical MWS, who almost always have whole gene deletions or truncating mutations (nonsense or frameshift) of ZFHX1B, suggesting that haploinsufficiency is the basis of MWS pathology. No obvious genotype-phenotype correlation could be identified so far, but atypical phenotypes have been reported with missense or splice mutations in the ZFHX1B gene. In this work we describe 40 novel mutations and we summarize the various mutational reports published since the identification of the causative gene.
Abnormalities, Multiple↗
DNA immobilisation procedures for surface plasmon resonance imaging (SPRI) based microarray systems.
Two different surface chemistries have been studied for the development of surface plasmon resonance imaging (SPRI) based DNA microarray affinity sensors: (1) 11-mercaptoundecanoic acid-poly(ethylenimine) (MUA-PEI) and (2) dextran procedures. The MUA-PEI method consists of assembling a multilayer on the basis of electrostatic interactions formed with: 11-mercaptoundecanoic acid (MUA), poly(ethylenimine) (PEI) and extravidin layers. The dextran procedure involves assembling a multilayer formed with 11-mercaptoundecanol, dextran and streptavidin layers, which are linked by covalent bonds. The oligonucleotide probes are immobilised onto the sensor surface as spots forming a matrix 14x14, which is spotted by a robot, while the target sequences are free in solution. The system allows the interaction (hybridisation) monitoring, in real-time and in parallel, of unlabeled oligonucleotide solution targets to oligonucleotide probes immobilised on a 196 spots matrix. Using oligonucleotides as probes and targets, both functionalised surfaces have been evaluated in view of their application to the diagnosis of gene mutations involved in human diseases. In particular, we demonstrate the ability to detect, in parallel, several mutations causing human cystic fibrosis (CF), which lie within exon 10 of the human cystic fibrosis transmembrane conductance regulator (CFTR) gene. The immobilised probes were complementary to sequences corresponding the mutant or wild type alleles. Two deletions of three bases (DeltaF508 and DeltaI507) and four single nucleotide polymorphisms (M470V, Q493X, V520F and 1716 G>A) were investigated. In both functionalised surfaces, the system showed the capacity to discriminate normal and mutant sequences differing by a single base.
Adsorption↗
Interactions between Sox10, Edn3 and Ednrb during enteric nervous system and melanocyte development.
The requirement for SOX10 and endothelin-3/EDNRB signalling pathway during enteric nervous system (ENS) and melanocyte development, as well as their alterations in Waardenburg-Hirschsprung disease (hypopigmentation, deafness and absence of enteric ganglia) are well established. Here, we analysed the genetic interactions between these genes during ENS and melanocyte development. Through phenotype analysis of Sox10;Ednrb and Sox10;Edn3 double mutants, we show that a coordinate and balanced interaction between these molecules is required for normal ENS and melanocyte development. Indeed, double mutants present with a severe increase in white spotting, absence of melanocytes within the inner ear, and in the stria vascularis in particular, and more severe ENS defects. Moreover, we show that partial loss of Ednrb in Sox10 heterozygous mice impairs colonisation of the gut by enteric crest cells at all stages observed. However, compared to single mutants, we detected no apoptosis, cell proliferation or overall neuronal or glial differentiation defects in neural crest cells within the stomach of double mutants, but apoptosis was increased in vagal neural crest cells outside of the gut. These data will contribute to the understanding of the molecular basis of ENS, pigmentation and hearing defects observed in mouse mutants and patients carrying SOX10, EDN3 and EDNRB mutations.
Animals↗
Sumoylation of the SOX10 transcription factor regulates its transcriptional activity.
SRY-related HMG box-containing factor 10 (SOX10) is a transcription factor essential for neural crest development and differentiation, and involved in Waardenburg syndrome type IV and PCWH syndrome. Here we show that the SOX10 protein is modified by sumoylation, a highly dynamic post-translational modification that affects stability, activity and localisation of some specific transcription factors. Three sumoylation consensus sites were found in the SOX10 protein, all of them are functional and modulate SOX10 activity. Sumoylation does not affect SOX10 sub-cellular localisation, but represses its transcriptional activity on two of its target genes, GJB1 and MITF, and modulates its synergy with its cofactors EGR2 and PAX3 on these promoters.
Amino Acid Sequence↗
Pure direct duplication (12)(q24.1-->q24.2) in a child with Marcus Gunn phenomenon and multiple congenital anomalies.
Partial trisomy of the region 12q24.1-->q24.2 is rare and usually associated with other rearrangements. We report on the clinical and cytogenetic findings in a girl with a pure de novo direct duplication dup(12)(q24.1-->q24.2). She had developmental and growth retardation, facial dysmorphism with upslanting palpebral fissures, wide downturned mouth, short neck, and Marcus Gunn phenomenon. She also had single transverse creases, hypoplasia of the corpus callosum, and cardiac malformations consisting of a bicuspid aortic valve, multiple ventricular septal defects, and kinking of the aorta. The size of the duplication was characterized by molecular cytogenetics and comparative genomic hybridization (CGH) to be 11.5 Mb in size and extended from the BAC probe RP11-256L11 loci (108.2 Mb) +/- 1 Mb to the BAC probe RP11-665J20 loci (119.7 Mb) +/- 1 Mb. No such pure 12q24 duplication was detected out of the 23 patients reported in the literature with duplications in 12q region. Comparison with these reported 12q trisomies suggests the duplication dup(12)(q24.1-->q24.2) is associated with a recognizable phenotype consisting of characteristic facial dysmorphism, growth retardation, and cardiac malformation.
Abnormalities, Multiple↗
Pyruvate kinase deficiency in France: a 3-year study reveals 27 new mutations.
Pyruvate kinase (PK) deficiency is the most common enzyme defect affecting the glycolytic pathway of the erythrocyte. Usually, it is clinically silent in heterozygotes but serious disorders are described at birth in homozygotes or compound heterozygotes. Including the mutants herein reported, more than 180 mutations of the PK-LR gene have now been identified. This 3-year study was carried out to detect mutations associated with disease-affecting families. Haematological indices, erythrocyte PK and glucose-6-phosphate dehydrogenase activities were measured. Molecular characterisation of the PK gene mutations included restriction enzyme analysis, mutation scanning and gene sequencing. Among the 56 families studied, nine homozygous cases and 41 different mutations were found. Eight mutations involved a splice site, 31 missense mutations were located in crucial domains of the molecule (catalytic site, cleft between the A and C domains, A/A' interface) and two cases of insertion-deletion were found. In total, 20 new mutations modifying the structure of the enzyme and seven affecting a splice site are reported. PK deficiency is an under diagnosed disease. However, deficiency could be life threatening in perinatal period and we report two lethal cases. These results support the characterisation of PK mutations, and show that prenatal diagnosis can identify affected infants and prepare safer conditions for the birth.
Anemia, Hemolytic, Congenital↗
Simultaneous molecular haplotyping of both IVS8 (TG)m and (T)n tracts in the CFTR gene: still a challenge.
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Cystic Fibrosis↗
Recurrence of Mowat-Wilson syndrome in siblings with the same proven mutation.
Mowat-Wilson syndrome (MWS) is a mental retardation syndrome associated with distinctive facial features, microcephaly, epilepsy, and a variable spectrum of congenital anomalies, including Hirschsprung disease (HSCR), agenesis of the corpus callosum, genitourinary abnormalities, and congenital heart disease. Heterozygous mutations or deletions involving the gene ZFHX1B (previously SIP1) [OMIM 605802] have recently been found to cause MWS. There have previously been no reports of a sibling recurrence of this syndrome. A brother and sister are described with clinical features of MWS, where both have the same truncating mutation in exon 8 of ZFHX1B. As their parents are phenotypically normal and do not have the mutation in lymphocyte-derived DNA, the most likely explanation is germ-line mosaicism.
Abnormalities, Multiple↗
A neutral variant involved in a complex CFTR allele contributes to a severe cystic fibrosis phenotype.
In order to further elucidate the contribution of complex alleles to the wide phenotypic variability of cystic fibrosis (CF), we investigated the structure-function relationships of a severe CF-associated complex allele [p.S912L;p.G1244V]. To evaluate the contribution of each mutation to the phenotype, cystic fibrosis transmembrane conductance regulator (CFTR) mutants were expressed in HeLa cells and analysed for protein processing and Cl- channel activity. Both p.G1244V and [p.S912L;p.G1244V] mutants had normal protein processing but markedly decreased Cl- channel activity compared with wild-type. Notably, the double mutant displayed a dramatic decrease in Cl- channel activity compared with p.G1244V (P<0.001). p.S912L had normal protein processing and no detectable impact on CFTR function. In other respects, the p.S912L variation was identified in compound heterozygosity with p.R709X in a healthy fertile man. Together, these data strongly support the view that p.S912L in isolation should be considered as a neutral variant but one that might significantly impair CFTR function when inherited in cis with another CFTR mutation. Our data also further document the contribution of complex alleles to the wide phenotypic variability of CF. The results of functional studies of such complex alleles in other genetic diseases are discussed.
Alleles↗
Misprocessing of the CFTR protein leads to mild cystic fibrosis phenotype.
Cystic fibrosis (CF) is mainly caused by mutations that interfere with the biosynthetic folding of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. The aim of this study was to determine the mechanism of dysfunction of a disease-causing mutation associated with variable phenotypes. In order to attain these objectives, we studied the effect of the p.L206W mutation on CFTR protein production and function, and we examined the genotype-phenotype correlation of [p.L206W]+[p.F508del] patients. We showed that p.L206W is a processing (class II) mutation since the CFTR biosynthetic pathway was severely impaired, whereas single-channel measurements indicated ion conductance similar to the wild-type protein. These data raise the larger question of the phenotypic variability of class II mutants, including p.F508del. Since multiple potential partners could modify the processing of the CFTR protein during its course to the cell surface, environmental and other genetic factors might contribute to this variability.
Adolescent↗
Trisomy 7 mosaicism, maternal uniparental heterodisomy 7 and Hirschsprung's disease in a child with Silver-Russell syndrome.
Prenatal trisomy 7 is usually a cell culture artifact in amniocytes with normal diploid karyotype at birth and normal fetal outcome. In the same way, true prenatal trisomy 7 mosaicism usually results in a normal child except when trisomic cells persist after birth or when trisomy rescue leads to maternal uniparental disomy, which is responsible for 5.5-7% of patients with Silver-Russell syndrome (SRS). We report here on the unusual association of SRS and Hirschsprung's disease (HSCR) in a patient with maternal uniparental heterodisomy 7 and trisomy 7 mosaicism in intestine and skin fibroblasts. HSCR may be fortuitous given its frequency, multifactorial inheritance and genetic heterogeneity. However, the presence of the trisomy 7 mosaicism in intestine as well as in skin fibroblasts suggests that SRS and HSCR might possibly be related. Such an association might result from either an increased dosage of a nonimprinted gene due to trisomy 7 mosaicism in skin fibroblasts (leading to SRS) and in intestine (leading to HSCR), or from an overexpression, through genomic imprinting, of maternally expressed imprinted allele(s) in skin fibroblasts and intestine or from a combination of trisomy 7 mosaicism and genomic imprinting. This report suggests that the SRS phenotype observed in maternal uniparental disomy 7 (mUPD(7)) patients might also result from an undetected low level of trisomy 7 mosaicism. In order to validate this hypothesis, we propose to perform a conventional and molecular cytogenetic analysis in different tissues every time mUPD7 is displayed.
Adult↗
Severe hemolytic anemia in a Vietnamese family, associated with novel mutations in the gene encoding for pyruvate kinase.
BACKGROUND AND OBJECTIVES: Chronic hemolytic anemias are very frequent diseases in intertropical countries mainly caused by hemoglobin disorders. We studied a Vietnamese family in which a first child suffered from a severe transfusion-dependent anemia. The family requested an antenatal diagnosis during a second pregnancy. To characterize the molecular defect, we studied the family over three generations. DESIGN AND METHODS: Blood from family members was sampled for a full hematologic evaluation, including enzymatic dosage, and DNA analysis was performed for patients displaying pyruvate kinase deficiency (PK-R). Mutation research on the 11 exons of the PKLR gene was done using a scanning method and sequencing. Deletion was evidenced by a Sybergreen based quantitative real time polymerase chain reaction (PCR) and mapped using quantitative multiplex PCR of short fluorescent fragments spread along the whole sequence of the PKLR gene. RESULTS: Hematologic and molecular studies of this severe chronic anemia demonstrated the existence of two defects in the PKLR gene, a new mutation located on exon 7: c.948C->G (N316K) and a large deletion extending from exon 4 to exon 10. INTERPRETATION AND CONCLUSIONS: We describe a family in a south-east Asian country; the proband had severe transfusion-dependent chronic anemia caused by the association between two PKLR gene mutations, PK Saigon (N316K) and PK Viet del 4-10. Severe chronic anemia could be induced by various molecular defects mainly affecting the globin genes. However, even in populations in which hemoglobin diseases are frequent, enzymatic diseases should be considered.
Adult↗
Connexin 32 promoter P2 mutations: a mechanism of peripheral nerve dysfunction.
We identified a large Charcot-Marie-Tooth disease family with a novel mutation in the Connexin 32 (Cx32) P2 promoter region at position -526bp. This mutation was in a highly conserved SOX10 binding site. Functional studies were conducted on the Cx32 promoter that showed that this mutation reduced the activity of the Cx32 promoter and the affinity for SOX10 binding. These data suggest that interaction between the Cx32 P2 promoter, SOX10, and EGR2 highlight a mechanism of peripheral nerve dysfunction.
Animals↗
An improved electronic microarray-based diagnostic assay for identification of MEFV mutations.
Recent technological advances, such as DNA chip devices that allow automated, high-throughput genotyping, promise to considerably improve the detection capability of single-nucleotide polymorphisms (SNPs) in clinically relevant genes. We used the NanoChip(R) Molecular Biology Workstation (Nanogen, www.nanogen.com) and recently introduced microelectronic array technology to develop a detection method for the more frequent mutations involved in familial Mediterranean fever (FMF), an autosomal recessive disease that affects several ethnic groups in the Mediterranean population, whose early diagnosis is crucial if severe complications are to be prevented. We adapted the previously described Nanogen procedures to FMF mutation analysis, introducing modifications that notably improve the technique. First, as the original procedure makes use of costly dye-tagged reporter sequences, we devised a universal reporter strategy, which was first evaluated and validated on the robust, previously established factor V Leiden and factor II (prothrombin) NanoChip diagnostic assays. FMF (MEFV), factor V (F5), and factor II (F2) genotypes identified using this improved system were totally concordant with results of other genotyping methods (denaturing gradient gel electrophoresis [DGGE], SSCP, and RFLP analysis). Second, we showed that the target sequences loaded on the NanoChip cartridges can be rehybridized several times in a highly reproducible manner, allowing sequential analysis of mutations. Thus, we devised a strategy that allows us to monitor the possible interference of additional mutations or SNPs at probe or stabilizer sequences. Finally, a comparative cost per sample analysis demonstrates that the accurate and reproducible FMF mutation detection assay we developed can be readily implemented in the clinical laboratory setting at reasonable expense.
Base Sequence↗
Pleiotropic and diverse expression of ZFHX1B gene transcripts during mouse and human development supports the various clinical manifestations of the "Mowat-Wilson" syndrome.
ZFHX1B encodes Smad-interacting protein 1, a transcriptional corepressor involved in the transforming growth factors beta (TGFbeta) signaling pathway. ZFHX1B mutations cause a complex developmental phenotype characterized by severe mental retardation (MR) and multiple congenital defects. We compared the distribution of ZFHX1B transcripts during mouse and human embryogenesis as well as in adult mice and humans. This showed that this gene is strongly transcribed at an early stage in the developing peripheral and central nervous systems of both mice and humans, in all neuronal regions of the brains of 25-week human fetuses and adult mice, and at varying levels in numerous nonneural tissues. Northern blot analysis suggested that ZFHX1B undergoes tissue-specific alternative splicing in both species. These results strongly suggest that ZFHX1B determines the transcriptional levels of target genes in various tissues through the combinatorial interactions of its isoforms with different Smad proteins. Thus, as well as causing neural defects, ZFHX1B mutations may also cause other malformations.
Alternative Splicing↗
Compound heterozygosity for two new mutations in the beta-globin gene [codon 9 (+TA) and polyadenylation site (AATAAA-->AAAAAA)] leads to thalassemia intermedia in a Tunisian patient.
More than 200 mutations that are associated with beta-thalassemia (thal) have been found. In most cases, studies to detect a mutation in a patient is made easier because of the existence of geographical sets of mutations that allow the use of a dedicated mutation detection kit. We describe here a patient who originated from Tunisia, in whom we found two as yet unreported mutations, showing that even in a well-studied population a full gene study might be needed to characterize mutation(s).
Adult↗
Quantitative real-time PCR assay for rapid identification of deletion carriers in hemophilia.
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Female↗