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P Guicheney

Publications and source records attributed to P Guicheney.

At least 55 records · Page 3Linked to original sources
PubMed2000

Multi-minicore disease--searching for boundaries: phenotype analysis of 38 cases.

Multi-minicore disease (MmD) is a congenital myopathy morphologically defined by the presence of multiple small zones of sarcomeric disorganization and lack of oxidative activity ("minicores") in muscle fibers. The dinical expression of MmD is considered to be greatly variable, and the morphological lesions are nonspecific; therefore, its boundaries are poorly defined, and its molecular bases are not known. To better define the phenotypic characteristics of MmD, we analyzed a large series of 38 patients with multiple minicores in muscle fibers in the absence of any other potential cause. According to clinical features, 4 subgroups were identified. Most patients (30 cases) shared a common highly consistent phenotype marked by the axial predominance of muscle weakness and a high occurrence of severe respiratory insufficiency and scoliosis ("classical" form). Other forms were characterized by pharyngolaryngeal involvement and total lack of head control (2 cases), antenatal onset with arthrogryposis (3 cases), and slowly progressive weakness with marked hand amyotrophy (3 cases). Type 1 fiber predominance and hypotrophy as well as centrally located nuclei were found in every subgroup. MmD is thus phenotypically heterogeneous, but a typical recognizable phenotype does exist. This phenotype classification should be helpful when undertaking research into the molecular defects that cause MmD.

Biopsy↗
PubMed1999

Splicing mutations in KCNQ1: a mutation hot spot at codon 344 that produces in frame transcripts.

BACKGROUND: Long-QT syndrome is a monogenic disorder that produces cardiac arrhythmias and can lead to sudden death. At least 5 loci and 4 known genes exist in which mutations have been shown to be responsible for the disease. The potassium channel gene KCNQ1, previously named KVLQT1, on chromosome 11p15.5 is one of these. METHODS AND RESULTS: We initially analyzed one family using microsatellite markers and found linkage to KCNQ1. Mutation detection showed a G to C change in the last base of exon 6 (1032 G-->C) that does not alter the coded alanine. Restriction digest analysis in the family showed that only affected individuals carried the mutation. A previous report suggested that a G to A substitution at the same position may act as a splice mutation in KCNQ1, but no data was given to support this hypothesis nor was the transcription product identified. We have shown by reverse-transcription polymerase chain reaction that 2 smaller bands were produced for the KCNQ1 gene transcripts in addition to the normal-sized transcripts when lymphocytes of affected individuals were analyzed. Sequencing these transcripts showed a loss of exon 7 in one and exons 6 and 7 in the other, but an in-frame transcript was left in each instance. We examined other families in whom long-QT syndrome was diagnosed and found another unreported splice-site mutation, 922-1 G-->C, in the acceptor site of intron 5, and 2 of the previously reported 1032 G-->A mutations. All these showed a loss of exons 6 and 7 in the mutant transcripts, validating the proposal that a consensus sequence is affected in the exonic mutations and that the integrity of the base at position 1032 is essential for correct processing of the transcript. CONCLUSIONS: The 6 cases already reported in the literature with the 1032 G-->A transition, the novel 1032 G-->C transversion, and a recent G-->T transversion at the same base show that codon 344 is the second most frequently mutated after codon 341, suggesting at least two hotspots for mutations in KCNQ1.

Child, Preschool↗
PubMed1999

Structure, genetic localization, and identification of the cardiac and skeletal muscle transcripts of the human integrin alpha7 gene (ITGA7).

We have determined the structure and the exon size pattern of the human integrin alpha7 subunit gene (ITGA7), which has been shown to be affected in a form of congenital myopathy. The gene is composed of at least 27 exons spanning a region of about 22.5 kb. The sequence of all exon/intron boundaries was determined and conforms to the GT/AG splicing consensus. We investigated the different splicing forms previously described in human and rodents. The major cytoplasmic variants alpha7A and alpha7B, which are developmentally regulated and tissue specific, were identified in human tissues, as well as the extracellular isoforms X1 and X2. The recently described D variant was detected in adult tissues by RT-PCR but not the C variant. We localized ITGA7 on chromosome 12q13 by high-resolution radiation hybrid mapping between D12S312 and D12S90 and identified a new CA-repeat microsatellite in intron 1.

Amino Acid Sequence↗
PubMed1999

C-terminal HERG mutations: the role of hypokalemia and a KCNQ1-associated mutation in cardiac event occurrence.

BACKGROUND: The long-QT syndrome (LQTS) is a genetically heterogeneous disease in which 4 genes encoding ion-channel subunits have been identified. Most of the mutations have been determined in the transmembrane domains of the cardiac potassium channel genes KCNQ1 and HERG. In this study, we investigated the 3' part of HERG for mutations. METHODS AND RESULTS: New specific primers allowed the amplification of the 3' part of HERG, the identification of 2 missense mutations, S818L and V822 M, in the putative cyclic nucleotide binding domain, and a 1-bp insertion, 3108+1G. Hypokalemia was a triggering factor for torsade de pointes in 2 of the probands of these families. Lastly, in a large family, a maternally inherited G to A transition was found in the splicing donor consensus site of HERG, 2592+1G-A, and a paternally inherited mutation, A341E, was identified in KCNQ1. The 2 more severely affected sisters bore both mutations. CONCLUSIONS: The discovery of mutations in the C-terminal part of HERG emphasizes that this region plays a significant role in cardiac repolarization. Clinical data suggests that these mutations may be less malignant than mutations occurring in the pore region, but they can become clinically significant in cases of hypokalemia. The first description of 2 patients with double heterozygosity associated with a dramatic malignant phenotype implies that genetic analysis of severely affected young patients should include an investigation for >1 mutation in the LQT genes.

Adolescent↗
PubMed1999

Genomic organization of the KCNQ1 K+ channel gene and identification of C-terminal mutations in the long-QT syndrome.

The voltage-gated K+ channel KVLQT1 is essential for the repolarization phase of the cardiac action potential and for K+ homeostasis in the inner ear. Mutations in the human KCNQ1 gene encoding the alpha subunit of the KVLQT1 channel cause the long-QT syndrome (LQTS). The autosomal dominant form of this cardiac disease, the Romano-Ward syndrome, is characterized by a prolongation of the QT interval, ventricular arrhythmias, and sudden death. The autosomal recessive form, the Jervell and Lange-Nielsen syndrome, also includes bilateral deafness. In the present study, we report the entire genomic structure of KCNQ1, which consists of 19 exons spanning 400 kb on chromosome 11p15.5. We describe the sequences of exon-intron boundaries and oligonucleotide primers that allow polymerase chain reaction (PCR) amplification of exons from genomic DNA. Two new (CA)n repeat microsatellites were found in introns 10 and 14. The present study provides helpful tools for the linkage analysis and mutation screening of the complete KCNQ1 gene. By use of these tools, five novel mutations were identified in LQTS patients by PCR-single-strand conformational polymorphism (SSCP) analysis in the C-terminal part of KCNQ1: two missense mutations, a 20-bp and 1-bp deletions, and a 1-bp insertion. Such mutations in the C-terminal domain of the gene may be more frequent than previously expected, because this region has not been analyzed so far. This could explain the low percentage of mutations found in large LQTS cohorts.

Base Sequence↗
PubMed1999

Genetic heterogeneity of congenital muscular dystrophy with rigid spine syndrome.

Rigid spine syndrome is a neuromuscular disorder characterised by early rigidity of the spine due to axial muscle contractures, generally associated with muscle weakness, limb-joint contractures, and often respiratory failure. This phenotype may be associated with several muscular diseases. In cases of merosin-positive congenital muscular dystrophies (CMD) with rigid spine syndrome, we have recently identified a new locus (RSMD1) on chromosome 1p35-36. In the present study, we report the clinical, morphological and genetic analysis of other patients affected by a CMD with rigid spine syndrome from nine consanguineous families. Homozygosity mapping showed that the disease was linked to RSMD1 in one of the nine families. The other families were excluded from RSMD1, and the patients presented highly variable phenotypes suggesting the involvement of more than one gene defect in rigid spine syndrome. Nevertheless, a subgroup of patients who never walked, and had very early rigidity of the spine and scoliosis, may be considered for further genetic analysis.

Adult↗
PubMed1999

Mutations in a dominant-negative isoform correlate with phenotype in inherited cardiac arrhythmias.

The long QT syndrome is characterized by prolonged cardiac repolarization and a high risk of sudden death. Mutations in the KCNQ1 gene, which encodes the cardiac KvLQT1 potassium ion (K+) channel, cause both the autosomal dominant Romano-Ward (RW) syndrome and the recessive Jervell and Lange-Nielsen (JLN) syndrome. JLN presents with cardiac arrhythmias and congenital deafness, and heterozygous carriers of JLN mutations exhibit a very mild cardiac phenotype. Despite the phenotypic differences between heterozygotes with RW and those with JLN mutations, both classes of variant protein fail to produce K+ currents in cultured cells. We have shown that an N-terminus-truncated KvLQT1 isoform endogenously expressed in the human heart exerts strong dominant-negative effects on the full-length KvLQT1 protein. Because RW and JLN mutations concern both truncated and full-length KvLQT1 isoforms, we investigated whether RW or JLN mutations would have different impacts on the dominant-negative properties of the truncated KvLQT1 splice variant. In a mammalian expression system, we found that JLN, but not RW, mutations suppress the dominant-negative effects of the truncated KvLQT1. Thus, in JLN heterozygous carriers, the full-length KvLQT1 protein encoded by the unaffected allele should not be subject to the negative influence of the mutated truncated isoform, leaving some cardiac K+ current available for repolarization. This is the first report of a genetic disease in which the impact of a mutation on a dominant-negative isoform correlates with the phenotype.

Adult↗
PubMed1999

[Congenital long QT syndrome. The value of genetics in prognostic evaluation].

The congenital long QT syndrome (QTL) is a heterogenic clinical and genetic entity characterised by prolongation of the QT interval which may be complicated by syncope and sudden death. Four genes have been identified for the cardiac potassium (KCNQ1, HERG and KCNE1) and sodium (SCN5A). The aim of this study was to assess the prognosis of the disease by the site of mutation identified on the morbid gene. Thirty-two genotyped families participated to this study. Each subject gave a clinical history, an ECG and a search for genetic mutation. Eighteen mutations in the transmembrane domains of KCNQ1 were identified in 25 families and 2 mutations in the C-terminal part were found in 4 families. The phenotype was less severe in C-terminal part mutations: less syncopes and sudden deaths (22 vs 55%, p < 0.001) and a shorter QTc (458 +/- 31 ms vs 479 +/- 31 ms, p = 0.0003). Three mutations were detected in the C-terminal part of HERG in 3 different families. Their phenotype was less severe with syncoped related to hypokalemia. The authors also report the case of a family in which two subjects who were the most severely affected had two mutations, one in HERG and the other in KCNQ1. This study confirms the value of a genetic research in assessing the severity of the congenital long QT syndrome.

Adolescent↗
PubMed1998

[Congenital long QT syndrome].

SEVERAL FORMS: Congenital long QT syndrome is a clinically (with and without deafness) and genetically (recessive or dominant autosomal inheritance) heterogeneous entity characterized by a long QT interval on the ECG associated with the risk of severe ventricular arrhythmia (torsade de pointes, ventricular fibrillation) and subsequent syncope or sudden death. GENETIC DATA: This rare familial syndrome is transmitted by different modes of inheritance and occurs in subjects with a morphologically normal heart. The severity of the prognosis justifies screening tests. The genetic origin of the disease has been confirmed and at least 5 loci and 4 genes have been identified, giving a perfect illustration of adrenergic ventricular rhythm disorders. Beta-blockers are used as first line treatment in symptomatic patients. PREVENTION: All drugs favoring QT interval lengthening are contraindicated in all subjects with a genetic anomaly. All members of the direct family must have a Holter recording and genotype in order to identify mutation carriers or asymptomatic patients.

Adrenergic beta-Antagonists↗
PubMed1998

Genotype-phenotype analysis in four families with mutations in beta-myosin heavy chain gene responsible for familial hypertrophic cardiomyopathy.

Familial hypertrophic cardiomyopathy is a genetically heterogeneous disease in which one of the most frequently implicated gene is the gene encoding the beta-myosin heavy chain. To date, more than 40 distinct mutations have been found within this gene. In order to progress on the determination of genotype-phenotype relationship, we have screened the beta-myosin heavy chain gene for mutations in 18 probands from unrelated families. We identified the mutation implicated in the disease in four families. Two of them, the Glu930 codon deletion and the Ile263Thr mutation, are reported here for the first time. The two other mutations are the Arg723Cys mutation, that was previously described in a proband as a de novo mutation, and the Arg719Trp mutation. A poor prognosis was associated with the Glu930codon deletion (mean maximal wall thickness (MWT) = 19.5 mm +/- 5) and the Arg719Trp mutation (mean MWT = 15.3 mm +/- 7), whereas a good prognosis was associated with the Arg723Cys mutation (mean MWT = 20.1 mm +/- 7). The combination of clinical and genetic characteristics of each family member suggests that prognosis is related neither to the degree of left ventricular wall thickness nor to a change in the net electrical charge of the protein. Additional family studies are needed to confirm these findings and to contribute to stratify the prognosis according to the mutation involved.

Adolescent↗
PubMed1998

Merosin-deficient congenital muscular dystrophy with severe mental retardation and normal cranial MRI: a report of two siblings.

The evidence of severe structural brain abnormalities in association with severe mental retardation is characteristic in congenital muscular dystrophy (CMD) forms other than the 'classical' form. However, it seems that the nosology of CMD is not complete yet, as we have clinical, immunohistochemical and genetic data suggesting that there are other unclassified forms. Here we report two CMD siblings from a consanguineous family with partial merosin-deficiency in muscle biopsies, severe mental retardation and normal MRI of the brain. The disease was not linked to the LAMA2 gene (6q22-23) or to Fukuyama congenital muscular dystrophy (FCMD) (9q31-33). To our knowledge, such an association may constitute a new entity within the broad clinical spectrum of CMD.

Brain↗
PubMed1998

A missense mutation in the alphaB-crystallin chaperone gene causes a desmin-related myopathy.

Desmin-related myopathies (DRM) are inherited neuromuscular disorders characterized by adult onset and delayed accumulation of aggregates of desmin, a protein belonging to the type III intermediate filament family, in the sarcoplasma of skeletal and cardiac muscles. In this paper, we have mapped the locus for DRM in a large French pedigree to a 26-cM interval in chromosome 11q21-23. This region contains the alphaB-crystallin gene (CRYAB), a candidate gene encoding a 20-kD protein that is abundant in lens and is also present in a number of non-ocular tissues, including cardiac and skeletal muscle. AlphaB-crystallin is a member of the small heat shock protein (shsp) family and possesses molecular chaperone activity. We identified an R120G missense mutation in CRYAB that co-segregates with the disease phenotype in this family. Muscle cell lines transfected with the mutant CRYAB cDNA showed intracellular aggregates that contain both desmin and alphaB-crystallin as observed in muscle fibers from DRM patients. These results are the first to identify a defect in a molecular chaperone as a cause for an inherited human muscle disorder.

Animals↗
PubMed1998

Diagnostic performance of QT interval variables from 24-h electrocardiography in the long QT syndrome.

AIMS: The long QT syndrome is mainly defined by QT interval prolongation (QTc > 0.44s). However, data obtained in genotyped patients showed that resting QTc measurement alone may be inaccurate for ascertaining the phenotype. The aim of this study was to evaluate the diagnostic performance of QT interval rate-dependence in untreated chromosome 11-linked patients. METHODS: The study population consisted of 25 untreated long QT patients linked to chromosome 11 and 25 age- and gender-matched controls. QTc intervals were measured on 12-lead resting ECG recordings. From 24-h Holter recordings, the slope of the relationship between ventricular repolarization and heart rate was studied separately day and night to assess neural modulation. Mean heart rates and rate-dependences of QT and Q-maximum of T (QTm) intervals were compared between long QT patients and controls for both time periods. RESULTS: In both groups, the rate-dependences were modulated by day-night influences. When compared to controls, long QT patients showed a significant increase at night in QT/RR slopes (0.158 +/- 0.05 vs 0.117 +/- 0.03, P = 0.002) and QTm/RR slopes (0.163 +/- 0.05 vs 0.116 +/- 0.04, P = 0.0006). Multivariate analysis, adjusting QTc interval on age and gender, discriminated between long QT patients and controls with a 76% sensitivity and a 84% specificity. A 96% sensitivity and a 96% specificity were reached by taking into account the QTm/RR slope at night, the QTc interval and the mean heart rate during the day. CONCLUSION: QT interval variables obtained from 24-h ECG recordings improve long QT syndrome diagnosis by showing an increased nocturnal ventricular repolarization rate-dependence in genotyped chromosome 11-linked patients.

Adolescent↗
PubMed1998

Familial hypertrophic cardiomyopathy. Cardiac ultrasonic abnormalities in genetically affected subjects without echocardiographic evidence of left ventricular hypertrophy.

AIMS: It is not known whether the apparent normality of echocardiographic examination results, in subjects bearing a mutation for hypertrophic cardiomyopathy but without ultrasonic left ventricular hypertrophy, is due to incomplete phenotypic expression, or inaccurate echocardiographic criteria. The aim of this study was to search for echocardiographic abnormalities in these patients. METHODS AND RESULTS: Echocardiography was performed in 100 subjects from two families with a mutation in the beta-MHC (720) or My-BPC (714) genes. We compared genetically affected subjects with an apparently normal left ventricle (thickness < 13 mm) (20 patients), and nonaffected first-degree relatives (61 normal subjects). (1) Patients had a thicker left ventricular wall (9.7 +/- 1.4 vs 8.9 +/- 1.4 mm, P = 0.03), a greater indexed mass (107 +/- 18 vs 97 +/- 17 g. m-2, P = 0.03), a larger left atrium (27 +/- 9 vs 23 +/- 10 mm3, P = 0.09) and lower wall stress (78 +/- 11 vs 89 +/- 15 10(3) dynes. cm-2, P = 0.002); these differences were highly significant after adjustment for height, age and systolic blood pressure either for wall thickness (P = 0.000003), mass (P = 0.005) or atrial volume (P = 0.001), and the ventricular systolic dimension appeared smaller (P = 0.01); (2) results remained significant (P < 0.01) when a lower cut-off value (< or = 11 mm) or only adults (> or = 18 years) were considered; (3) a subanalysis of Family 714 (13 patients, 25 normals matched for sex, age and height) showed the same trends. CONCLUSION: In familial hypertrophic cardiomyopathy, genetically affected subjects with an apparently normal heart by echocardiography show slight ultrasonic structural and functional left ventricular modifications, suggesting that the phenotype of the disease is a continuous spectrum from normal structure to typical hypertrophy.

Adolescent↗
PubMed1998

Identification of a new locus for a peculiar form of congenital muscular dystrophy with early rigidity of the spine, on chromosome 1p35-36.

Classical congenital muscular dystrophies (CMDs) are autosomal recessive neuromuscular disorders characterized by early onset of hypotonia and weakness, atrophy of limbs and trunk muscles, contractures, and dystrophic changes in the muscle biopsy. So far, only one gene, LAMA2 (6q2), which encodes the laminin alpha2 chain (or merosin), has been identified in these disorders. Mutations in LAMA2 cause CMD with complete or partial merosin deficiency, detectable by immunocytochemistry on muscle biopsies, and account for approximately 50% of CMD cases. In a large consanguineous family (11 siblings) comprising three children affected by CMD without merosin deficiency, we undertook a genomewide search by homozygosity mapping and analyzed 380 microsatellite markers. The affected children were homozygous for several markers on chromosome 1p35-36. We identified two additional consanguineous families with affected children who also showed linkage to this locus. A maximum cumulative LOD score of 4.48, at a recombination fraction of .00, was obtained with D1S2885. A consistent feature in these three families was the presence of early rigidity of the spine, scoliosis, and reduced vital capacity, as found in rigid-spine syndrome (RSS). This study is the first description of a locus for a merosin-positive CMD and will help to better define the nosology of RSS.

Adolescent↗
PubMed1998

Mutation in the human acetylcholinesterase-associated collagen gene, COLQ, is responsible for congenital myasthenic syndrome with end-plate acetylcholinesterase deficiency (Type Ic).

Congenital myasthenic syndrome (CMS) with end-plate acetylcholinesterase (AChE) deficiency is a rare autosomal recessive disease, recently classified as CMS type Ic (CMS-Ic). It is characterized by onset in childhood, generalized weakness increased by exertion, refractoriness to anticholinesterase drugs, and morphological abnormalities of the neuromuscular junctions (NMJs). The collagen-tailed form of AChE, which is normally concentrated at NMJs, is composed of catalytic tetramers associated with a specific collagen, COLQ. In CMS-Ic patients, these collagen-tailed forms are often absent. We studied a large family comprising 11 siblings, 6 of whom are affected by a mild form of CMS-Ic. The muscles of the patients contained collagen-tailed AChE. We first excluded the ACHE gene (7q22) as potential culprit, by linkage analysis; then we mapped COLQ to chromosome 3p24.2. By analyzing 3p24.2 markers located close to the gene, we found that the six affected patients were homozygous for an interval of 14 cM between D3S1597 and D3S2338. We determined the COLQ coding sequence and found that the patients present a homozygous missense mutation, Y431S, in the conserved C-terminal domain of COLQ. This mutation is thought to disturb the attachment of collagen-tailed AChE to the NMJ, thus constituting the first genetic defect causing CMS-Ic.

Acetylcholinesterase↗
PubMed1998

PCR based mutation screening of the laminin alpha2 chain gene (LAMA2): application to prenatal diagnosis and search for founder effects in congenital muscular dystrophy.

Classical congenital muscular dystrophy with merosin deficiency is caused by mutations in the laminin alpha2 chain gene (LAMA2). Extended sequencing of the introns flanking the 64 LAMA2 exons was carried out and, based on these sequences, oligonucleotide primers were designed to amplify the coding region of each exon separately. By PCR-SSCP analysis, we identified eight new mutations in nine families originating from various countries. All induced a premature truncation of the protein, either in the short arm or in the globular C-terminal domain. A 2 bp deletion in exon 13, 2098delAG, was found in three French non-consanguineous families and a nonsense mutation of exon 20, Cys967stop, in two other non-consanguineous families originating from Italy. Determination of rare intragenic polymorphisms permitted us to show evidence of founder effects for these two mutations suggesting a remote degree of consanguinity between the families. Other, more frequent polymorphisms, G to A 1905 (exon 12), A to G 2848 (exon 19), A to G 5551 (exon 37), and G to A 6286 (exon 42), were used as intragenic markers for prenatal diagnosis. This study provides valuable methods for determining the molecular defects in LAMA2 causing merosin deficient congenital muscular dystrophy.

Child↗