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PubMed2001

Acetylcholine receptor delta subunit mutations underlie a fast-channel myasthenic syndrome and arthrogryposis multiplex congenita.

Limitation of movement during fetal development may lead to multiple joint contractures in the neonate, termed arthrogryposis multiplex congenita. Neuromuscular disorders are among the many different causes of reduced fetal movement. Many congenital myasthenic syndromes (CMSs) are due to mutations of the adult-specific epsilon subunit of the acetylcholine receptor (AChR), and, thus, functional deficits do not arise until late in gestation. However, an earlier effect on the fetus might be predicted with some defects of other AChR subunits. We studied a child who presented at birth with joint contractures and was subsequently found to have a CMS. Mutational screening revealed heteroallelic mutation within the AChR delta subunit gene, delta 756ins2 and delta E59K. Expression studies demonstrate that delta 756ins2 is a null mutation. By contrast, both fetal and adult AChR containing delta E59K have shorter than normal channel activations that predict fast decay of endplate currents. Thus, delta E59K causes dysfunction of fetal as well as the adult AChR and would explain the presence of joint contractures on the basis of reduced fetal movement. This is the first report of the association of AChR gene mutations with arthrogryposis multiplex congenita. It is probable that mutations that severely disrupt function of fetal AChR will underlie additional cases.

Action Potentials↗
PubMed2000

Evidence for a new locus for X-linked retinitis pigmentosa (RP23).

PURPOSE: X-linked retinitis pigmentosa (XLRP) is a degenerative disease of the retina characterized in the early stages of disease by night blindness as a result of rod photoreceptor loss, progressing to severe disease with loss of central vision by the third decade in affected males. XLRP displays exceptional genetic heterogeneity, with five reported loci on the human X-chromosome. To investigate the level of heterogeneity for XLRP in the patient pool in the current study, extensive haplotype analysis, linkage analysis, and mutation screening were performed. METHODS: Haplotype analysis of a family with diagnosed XLRP was scored with more than 34 polymorphic markers spanning the entire X-chromosome, including regions already identified as harboring XLRP genes and retina-specific genes. Two-point and multipoint lod scores were calculated. Affected male DNA was amplified with primers specific for the retinoschisis gene (XLRS1), and the products were screened for nucleic acid alterations by direct automated sequencing. RESULTS: In this article haplotype and linkage data are presented identifying a new locus for XLRP on the short arm of the X-chromosome, distinct from previously reported gene localizations for XLRP. The phenotype is atypical, in that the onset of vision loss in the male members of this family is unusually early, and female obligate carriers have normal fundi and waveforms. Informative recombination events in this family define a locus for XLRP (RP23) on Xp22 between the markers DXS1223 and DXS7161, spanning approximately 15 cM. A maximum lod score of 2.1 was calculated for the locus order DXS7103-8 cM-(RP23/DXS1224)-4 cM-DXS999. This new locus (RP23) encompasses the retinoschisis disease gene; therefore, XLRS1 was screened for a mutation. No sequence alteration was identified indicating that mutations in the coding region of the gene responsible for retinoschisis do not cause RP23. CONCLUSIONS: The results describe evidence for a new locus for XLRP (RP23), adding to the established genetic heterogeneity for this disease and the number of genes expressed in ocular tissue residing on the X-chromosome.

Adult↗
PubMed2002

High-throughput screening for GJB2 mutations--its clinical application to genetic testing in prelingual deafness screening for GJB2 mutations.

OBJECTIVES: Mutations in connexin26 (GJB2) are one of the most frequent causes of prelingual hearing impairment. Several different types of one-base deletions in exon2 were the most common type of GJB2 mutation regardless of ethnicity, including 35delG in American-European populations, 235delC in Japanese population and 167delT in Ashkenazi Jewish population. Various types of one-base substitutions were also considered to be causative mutations of GJB2 associated hearing impairment. This article describes a rapid and high-throughput screening procedure for the detection of one-base deletion/substitution in GJB2 with less invasive sampling procedure in the implication for the clinical application. METHODS: 53 hearing-impaired children and 50 healthy controls were admitted to take part in this study program. DNA samples obtained from buccal swab were used to amplify the exon2 of GJB2, and single run with an automated sequencer was used to identify the one-base deletion. Single-base substitutions were also screened by primer-extension procedure with dye terminators. The presence of both types of mutations was confirmed by direct sequence of the GJB2 exon2. RESULTS: Two of 50 controls (4%) included one-base deletion in GJB2 as heterozygote. 14 of 53 hearing impaired cases (26.4%) contained deletion in GJB2 either as homozygote (five cases) or heterozygote (nine cases) form. Sequencing analysis of whole exon2 of GJB2 identified all these deletions as 235delC. Primer-extension analysis revealed additional mutations with single base substitutions in three cases with compound heterozygote with 235delC. CONCLUSIONS: Rapid screening procedure of GJB2 can be potentially useful for the identification of prelingual deafness.

Chromosome Deletion↗
PubMed2003

Simultaneous use of DGGE and DHPLC to screen TP53 mutations in cancers of the esophagus and cardia from a European high incidence area (Lower Normandy, France).

We investigated TP53 mutation patterns in cancers of the esophagus and cardia of patients coming from Lower Normandy, a region situated in the highest incidence area in Europe. To screen tumor samples, we first used denaturing gradient gel electrophoresis (DGGE), a well-characterized technique which constituted our reference method. Then the results were compared with those obtained by denaturing high performance liquid chromatography (DHPLC), a recent and automatic screening technology. Analysis of the TP53 mutations profile showed that the detected alterations were mainly point mutations. Ninety-seven percent (33/34) of esophageal squamous cell carcinoma samples presented at least one mutation or polymorphism. The proportion of somatic, non-silent and sequence-confirmed mutations was 76% (26/34). The most common substitutions were G-->A transitions, which could be related to nitrosamines, acetaldehyde or factors prone to producing mucosal irritation, like hot beverages. G-->T transversions, which were also frequently detected, could originate from benzo[a]pyrene in tobacco smoke. A-->T transversions were not revealed in our series, which constitutes a discordance with mutational spectra already performed in north-western France. Concerning adenocarcinoma of the esophagus and cardia, the alteration frequency was 69% (11/16), with a majority of G-->A transitions at CpG dinucleotides. They are probably related to endogenous process mediated by inflammatory diseases like gastro-esophageal reflux and Barrett's esophagus. The main advantage provided by DHPLC was its ease of application. However, the optimization steps turned out to be quite critical, especially for sequences with high melting temperatures embedded in lower melting temperature fragments. Considering only the common sequences analyzed by the two techniques, four of the 46 positive samples detected by DGGE were not revealed by DHPLC. This result stresses the limited sensitivity of DHPLC compared with DGGE under the conditions described in this study.

Cardia↗
PubMed1996

Screen for mutations affecting development of Zebrafish neural crest.

The neural crest provides a useful model to learn how cell fate diversification is regulated during vertebrate development. Our approach is to isolate zebrafish mutations in which the development of neural crest derivatives is disrupted, in order to learn about the underlying genetic mechanisms. We describe a screen in which parthenogenetic diploid embryos are examined both for visible phenotypes and for cellular defects in neural crest-derived sensory neurons recognized immunohistochemically. We present preliminary results from this screen and briefly describe a few representative mutations. We also discuss the general utility of our strategy and comment on the future directions of this approach.

Animals↗
PubMed1998

Mutations in the liver glycogen synthase gene in children with hypoglycemia due to glycogen storage disease type 0.

Glycogen storage disease type 0 (GSD-0) is a rare form of fasting hypoglycemia presenting in infancy or early childhood and accompanied by high blood ketones and low alanine and lactate concentrations. Although feeding relieves symptoms, it often results in postprandial hyperglycemia and hyperlactatemia. The glycogen synthase (GS) activity has been low or immeasurable in liver biopsies, whereas the liver glycogen content has been only moderately decreased. To investigate whether mutations in the liver GS gene (GYS2) on chromosome 12p12.2 were involved in GSD-0, we determined the exon-intron structure of the GYS2 gene and examined nine affected children from five families for linkage of GSD-0 to the GYS2 gene. Mutation screening of the 16 GYS2 exons was done by single-strand conformational polymorphism (SSCP) and direct sequencing. Liver GS deficiency was diagnosed from liver biopsies (GS activity and glycogen content). GS activity in the liver of the affected children was extremely low or nil, resulting in subnormal glycogen content. After suggestive linkage to the GYS2 gene had been established (LOD score = 2.9; P < 0.01), mutation screening revealed several different mutations in these families, including a premature stop codon in exon 5 (Arg246X), a 5'-donor splice site mutation in intron 6 (G+1T--> CT), and missense mutations Asn39Ser, Ala339Pro, His446Asp, Pro479Gln, Ser483Pro, and Met491Arg. Seven of the affected children carried mutations on both alleles. The mutations could not be found in 200 healthy persons. Expression of the mutated enzymes in COS7 cells indicated severely impaired GS activity. In conclusion, the results demonstrate that GSD-0 is caused by different mutations in the GYS2 gene.

Animals↗
PubMed2003

Screening for mutations in BMP4 and FOXC1 genes in congenital anomalies of the kidney and urinary tract in humans.

Recent studies have demonstrated in mice that bone morphogenetic protein 4 (BMP4) and forkhead transcription factor 1 (FOXC1) are involved in the organogenesis of the kidney and urinary tract and that derangement of either gene, BMP4 or FOXC1, leads to development of congenital anomalies of the kidney and urinary tract (CAKUT). In order to determine whether human CAKUT is associated with abnormalities in BMP4 or FOXC1, we established a PCR-based methodology for the DNA sequence analysis of BMP4 and FOXC1 in humans. Our initial screening identified an insertion mutation in FOXC1 with a triplet GGC in three of the seven patients with CAKUT. In the present study, no mutation was detected in the coding sequence of BMP4.

Animals↗
PubMed2000

Evaluation of enzymatic mutation detectiontrade mark in hereditary nonpolyposis colorectal cancer.

In hereditary nonpolyposis colorectal cancer (HNPCC), the majority of reported mutations are dispersed throughout the 35 exons of the two principal susceptibility genes, MLH1 and MSH2, and because of this complexity, rapid mutation screening methods are required. The aim of this study was to evaluate the sensitivity of the Enzymatic Mutation Detection (EMD) assay in HNPCC using genomic DNA samples with known gene alterations in MLH1 and MSH2. The EMD assay relies upon the enzyme T4 Endonuclease VII recognizing and cleaving DNA mismatches, created when a PCR product containing a sequence alteration is hybridized with a wild type probe. A total of 68 different sequence variants from 30 exons were analyzed. The EMD assay was able to detect 62 of the 68 sequence variants (91%) with the majority showing strong cleavage products. One of the advantages of the EMD assay over other mutation screening techniques is that larger fragments can be analyzed in a single assay. No specialized equipment is required and one set of primers is sufficient for radioactive detection of the cleavage products. This method can be adapted to use fluorescent dye-labelled primers and may be automated to detect mutations accurately and rapidly in a large number of samples. One new MLH1 mutation (418delA) and two novel MSH2 mutations (1A>C; 227-228delAG) were also detected in HNPCC patients screened using this method.

Adaptor Proteins, Signal Transducing↗
PubMed1998

A screen for mutations that prevent lethality caused by expression of activated sevenless and Ras1 in the Drosophila embryo.

Ras1 plays a critical role in receptor tyrosine kinase (RTK) signal transduction pathways that function during Drosophila development. We demonstrate that mis-expression of constitutively active forms of Ras1 (Ras1V12) and the Sevenless (Sev) RTK (SevS11) during embryogenesis causes lethality due to inappropriate activation of RTK/Ras1 signaling pathways. Genetic and molecular data indicate that the rate of SevS11/sev-Ras1V12 lethality is sensitive to the expression level of both transgenes. To identify genes that encode components of RTK/Ras1 signaling pathways or modulators of RNA polymerase II transcription, we took advantage of the dose-sensitivity of the system and screened for second site mutations that would dominantly suppress the lethality. The collection of identified suppressors includes the PR55 subunit of Protein Phosphatase 2A indicating that downstream of Sev and Ras1 this subunit acts as a negative regulator of phosphatase activity. The isolation of mutations in the histone deacetylase RPD3 suggests that it functions as positive regulator of sev enhancer-driven transcription. Finally, the isolation of mutations in the Trithorax group gene devenir and the characterized allelism with the Breathless RTK encoding gene provides evidence for Ras1-mediated regulation of homeotic genes.

Animals↗
PubMed2003

A P-element insertion screen identified mutations in 455 novel essential genes in Drosophila.

With the completion of the nucleotide sequences of several complex eukaryotic genomes, tens of thousands of genes have been predicted. However, this information has to be correlated with the functions of those genes to enhance our understanding of biology and to improve human health care. The Drosophila transposon P-element-induced mutations are very useful for directly connecting gene products to their biological function. We designed an efficient transposon P-element-mediated gene disruption procedure and performed genetic screening for single P-element insertion mutations, enabling us to recover 2500 lethal mutations. Among these, 2355 are second chromosome mutations. Sequences flanking >2300 insertions that identify 850 different genes or ESTs (783 genes on the second chromosome and 67 genes on the third chromosome) have been determined. Among these, 455 correspond to genes for which no lethal mutation has yet been reported. The Drosophila genome is thought to contain approximately 3600 vital genes; 1400 are localized on the second chromosome. Our mutation collection represents approximately 56% of the second chromosome vital genes and approximately 24% of the total vital Drosophila genes.

Animals↗
PubMed2003

Simultaneous (AC)n microsatellite polymorphism analysis and single-stranded conformation polymorphism screening is an efficient strategy for detecting ankyrin-1 mutations in dominant hereditary spherocytosis.

Nonsense/stop mutations in the ankyrin-1 gene (ANK1) are a major cause of dominant HS (dHS) (frequency of 23% in German dHS patients). To date, no common mutation has been found and therefore a simple mutation screening is not feasible. The reduced expression of one cDNA allele in the (AC)n microsatellite polymorphism of the ankyrin-1 gene, as seen in about 20% of Czech patients with dHS, may identify candidates with a possible frameshift/nonsense mutation. In order to verify the efficiency of this screening we screened the ankyrin-1 gene of 22 Czech dHS patients for both the reduced cDNA allele expression in the frequent (AC)n and the common exonic 26/39 polymorphisms, as well as for polymerase chain reaction (PCR) single-stranded conformation polymorphisms in any one of the 42 exons of ANK1. Anomalous PCR products were sequenced. We found seven new ANK1 frameshift/nonsense mutations in nine patients with, but in none of six patients without, a reduced cDNA allele expression (efficiency of 78%). We conclude that screening of dHS patients for such a reduced allele expression in common ANK1 polymorphisms is an efficient procedure for the identification of candidates for frameshift/nonsense mutations in the ankyrin-1 gene.

Ankyrins↗
PubMed1995

Allele-specific associated polymorphism analysis: novel modification of SSCP for mutation detection in heterozygous alleles using the paradigm of resistance to thyroid hormone.

Allele-specific polymorphism (ASAP) analysis is a modification of single-strand conformation polymorphism (SSCP) mutation screening under optimized temperature conditions in a minigel format with ethidium bromide detection. ASAP analysis was used to screen for and identify mutations within the human thyroid hormone receptor-beta (hTR-beta) gene. These mutations are the underlying cause of resistance to thyroid hormone (RTH). Eleven dissimilar known hTR-beta mutations and six previously uncharacterized mutations were accurately identified. ASAP screening extends to unique ASAP-DNA fingerprinting as an identifying signature for each novel hTR-beta mutation detected thus far. Gel-plugs from the SSCP gels containing polymorphic single-stranded DNA alleles were used without elution to prepare solid-phase sequencing templates for mutant allele PCR and sequencing (MAPS). The coupling of ASAP analysis with MAPS has eliminated many of the interpretative and technical problems associated with the sequencing of heterozygous alleles. Together, this convenient screening and sequencing methodology offers accuracy, reproducibility, speed, and the potential elimination of all radioactivity, providing a general strategy for future automated detection and characterization of genetic mutations.

Adolescent↗
PubMed1995

Screening for mutations at codon 717 of the amyloid precursor protein gene in Alzheimer's disease.

Three kinds of missense mutation at codon 717 of amyloid precursor protein (APP) gene (Val --> Ile; Val --> Gly; Val --> Phe) were screened in 114 patients with familial and sporadic Alzheimer's disease (AD), using a rapid testing method for each Val --> Gly and Val --> Phe mutation and Goate's method for Val --> Ile mutation based on the polymerase chain reaction. Mutations were not found in the subjects, confirming earlier suggestions that these three mutations at codon 717 of APP gene account for only a small proportion of cases of not only familial AD but also sporadic AD.

Aged↗
PubMed2007

Paget's disease of bone in the French population: novel SQSTM1 mutations, functional analysis, and genotype-phenotype correlations.

UNLABELLED: Mutation screening of the SQSTM1 gene in 94 French patients with PDB revealed two novel point-mutations (A381V and L413F) and two new compound heterozygous genotypes (P392L/A381V and P392L/A390X). Functional analysis showed an increased level of SQSTM1/p62 protein in PDB patients and truncated forms of the protein encoded by the A390X allele. Clinical data indicate that PDB patients with SQSTM1 mutation are younger at PDB diagnosis and have more extensive bone lesions. INTRODUCTION: Paget's disease of bone (PDB) is a common chronic disease of the skeleton, with a strong genetic component. A recurrent mutation (P392L) was first identified on chromosome 5, in the Sequestosome 1 (SQSTM1) gene. Several other mutations of the SQSTM1 gene have been described in PDB patients, affecting the ubiquitin-associated domain (UBA) of the SQSTM1/p62 protein. The objectives of this study were to evaluate the frequency of the SQSTM1 mutations in French PBD patients, to study the expression of the SQSTM1/p62 protein, and to search for genotype-phenotype correlations. MATERIALS AND METHODS: Blood was obtained from 94 unrelated French PDB patients and 100 controls for mutation screening of exons 7 and 8, encoding for the UBA domain of SQSTM1. Epstein-Barr virus (EBV)-immortalized B-cell lymphocytes were established from 13 patients, giving access to functional analysis of the gene and the SQSTM1/p62 expressions using real-time PCR and Western blot. RESULTS: Mutations of the SQSTM1 gene were identified in 12 of the 94 PDB patients (13%). Eight patients carried P392L. Two novel missense mutations were identified: L413F and A381V. This A381V mutation and A390X were found in distinct patients already carriers of P392L. The SQSTM1/p62 protein expression in PDB patients increased when zero, one, or two mutations were present, and SQSTM1 truncated forms were associated with the A390X mutation. The mean age of PDB diagnosis was younger in patients with the SQSTM1 mutation. PDB was more extensive in patients who carried a SQSTM1 mutation. CONCLUSIONS: Mutations of SQSTM1 are present in the French population. PDB patients with and without the SQSTM1 mutation have an increased level of SQSTM1/p62, caused by overproduction of the protein, probably involved in the pathophysiology of PDB. The presence of the SQSTM1 mutation may be a worsening factor for PDB.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Systematic screening for mutations in the human serotonin 1F receptor gene in patients with bipolar affective disorder and schizophrenia.

Using single strand conformational analysis we screened the complete coding sequence of the serotonin 1F (5-HT1F) receptor gene for the presence of DNA sequence variation in a sample of 137 unrelated individuals including 45 schizophrenic patients, 46 bipolar patients, as well as 46 healthy controls. We detected only three rare sequence variants which are characterized by single base pair substitutions, namely a silent T-->A transversion in the third position of codon 261 (encoding isoleucine), a silent C-->T transition in the third position of codon 176 (encoding histidine), and an C-->T transition in position -78 upstream from the start codon. The lack of significant mutations in patients suffering from schizophrenia and bipolar affective disorder indicates that the 5-HT1F receptor is not commonly involved in the etiology of these diseases.

Base Sequence↗
PubMed2006

MutScreener: primer design tool for PCR-direct sequencing.

In searching for susceptibility genes, both positional cloning and candidate gene strategies have been helpful. Mutation screening is one of the many technologies that have been implemented in order to identify mutations or polymorphisms in candidate genes or genomic regions. Since human genome sequence is available, PCR-direct sequencing is one of the major methods for mutation screening or resequencing. Unfortunately, assay design can be laborious if multiple genes or large regions need to be investigated. To solve this conundrum a web-based application, MutScreener, has been developed. MutScreener assists in the analysis of human gene structure and design of PCR/sequencing primer. This application supports batch assay design based on either existing public gene annotation or custom gene annotation. The optional universal tagged primers can support high throughput resequencing processes. MutScreener is available for public use at http://bioinfo.bsd.uchicago.edu/MutScreener.html.

DNA Primers↗
PubMed2006

Genetic analysis of a family with 46,XY "female" associated with infertility.

Genetic analysis of a family with 46,XY "female" associated with infertility was performed using the conventional G-banding and gene mutation screening. The karyotypes of the two female patients were 46,XY and those of their parents were normal. The mutation screenings in sex-determining region Y (SRY) gene and androgen receptor (AR) gene were carried out. No mutation has been found in the whole coding sequence of SRY gene. The mutation of codon 840 CGT (arginine) to CAT (histidine) of AR gene led to the infertility in the patients. The patients showed androgen insensitivity. The clinical phenotype of theirs presented more deleteriously than and different from the one reported before, though they had the same mutation of codon 840 CGT (arginine) to CAT (histidine) of AR gene, which was very different from the mutation of 840 CGT (arginine) to TGT (cysteine) at the same codon.

Adolescent↗