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At least 649 records · Page 36Linked to original sources
PubMed1998

[Update on a diagnostic test for choroideremia: the protein truncation test (PTT)].

PURPOSE: The aim of this study was to define the RT-PCR-PTT parameters for CHM gene analysis and to evaluate its interest as a method for CHM mutation screening. METHODS: The entire CHM coding region was reversed-transcribed in three overlapping cDNA segments (RT-PCR) which were amplified and further analyzed by PTT after in vitro transcription/translation. RESULTS: This strategy enabled us to detect a truncated peptide in each of the 6 unrelated patients from southern France who were investigated. The mutation was further characterized by direct sequencing of the RT-PCR product. CONCLUSION: In CHM gene, all conditions are present to make the RT-PCR-PTT strategy the method of choice for mutation screening. As a result of the simplified protocol described in this study, the families of the patients could benefit from accurate carrier-status assessment.

Adaptor Proteins, Signal Transducing↗
PubMed2001

MODY in Iceland is associated with mutations in HNF-1alpha and a novel mutation in NeuroD1.

AIMS/HYPOTHESIS: Five different types of maturity-onset diabetes of the young (MODY) have been identified until now but mutation screening suggests that more MODY genes exist. Mutations in genes encoding transcription factors essential for normal development and function of pancreatic beta cells has recently become important in studying the genetics of Type II (non-insulin-dependent) diabetes mellitus. Patients with MODY and their families in Iceland were screened for mutations in the transcription factor genes. METHODS: Clinical and biochemical information on individuals with MODY was collected and their family trees constructed. Linkage analysis was carried out on chromosomal regions known to harbour genes previously shown to be associated with MODY. Mutations were identified by direct sequencing. RESULTS: Three families were identified. Two of these showed linkage to chromosome 12 and carried mutations in exon 4 of the HNF-1alpha gene (290fsdelC and R272C). However, the third family showed no linkage to the previously described MODY genes but shared a novel mutation in the NeuroD1 gene on chromosome 2q32. This mutation, a glutamate to lysine substitution at codon 110, resides in the basic domain of the protein. CONCLUSION/INTERPRETATION: Mutations in MODY subjects have been identified in the Icelandic population. In addition this study identified the NeuroD1 gene as the gene responsible for the sixth type of MODY.

Age of Onset↗
PubMed2000

Linkage and association studies between the proopiomelanocortin (POMC) gene and obesity in caucasian families.

AIMS/HYPOTHESIS: The region 2p21-23, containing the proopiomelanocortin gene (POMC), was reported to be linked to leptin concentrations in Mexican-American, French and African-American cohorts. A polyhormone peptide, POMC is expressed in brain, gut, placenta and pancreas. The POMC mutations are responsible for rare cases of early-onset obesity. Thus we examined the contribution of the POMC locus to obesity in French families. METHODS: Single and multipoint linkage studies were done between obesity, obesity associated-phenotypes (leptin values and z-score of the body mass index) and three newly mapped markers surrounding POMC in 264 affected sib-pairs from French obese families. Mutation screening of the exons and intron/exon junctions of the POMC gene was realised by direct sequencing. Association studies were done in 379 unrelated obese patients and 370 non-obese non-diabetic subjects. RESULTS: Linkage analysis confirmed the trend towards linkage between polymorphic markers around POMC and variations of leptin concentrations and z-score (maximum lod score at D2S2337 = 2.03). Mutation screening of the POMC gene in the French Caucasian cohort identified two previously reported polymorphisms. None of these variants was associated with obesity, diabetes or serum leptin and lipid concentrations. CONCLUSION/INTERPRETATION: Our results indicate that mutations in the POMC gene do not contribute to the variance of obesity associated phenotypes, at least in French Caucasians. Given the replicated evidence of linkage between leptin values and the chromosome 2p21-23 region in different populations, it is likely that functional variant(s) in the POMC regulating sequences or in an unknown gene in this region explains this linkage.

Body Mass Index↗
PubMed2006

Evidence of genetic heterogeneity in MRCS (microcornea, rod-cone dystrophy, cataract, and posterior staphyloma) syndrome.

PURPOSE: To present the detailed phenotype of a subject with MRCS (microcornea, retinal dystrophy, cataract, and posterior staphyloma) syndrome and to investigate the underlying molecular genetic basis. DESIGN: Interventional case report. METHODS: Clinical examination, electrophysiologic assessment, B-scan ultrasonography, and mutation screening of the gene VMD2. The protocol of the study was approved by the local ethics committee and informed consent was obtained. RESULTS: A 12-year-old boy was identified with bilateral microcornea, rod-cone dystrophy, congenital cataracts, and posterior staphylomata associated with high myopia (MRCS). Mutation screening failed to identify disease-causing sequence variants in VMD2, the gene associated with MRCS syndrome. All previous subjects have had pathogenic VMD2 sequence alterations. CONCLUSIONS: We present a further report of the MRCS syndrome and provide evidence in support of genetic heterogeneity in this phenotype.

Bestrophins↗
PubMedDate not supplied

Porphyrias.

Seven different porphyrias form a group of inherited metabolic disorders, each resulting from a partial deficiency of a specific enzyme in the haem biosynthesis pathway. Clinically, the three most important entities are an acute porphyric attack and acute and chronic skin symptoms. Porphyrias are rare and sometimes misdiagnosed, because various symptoms and signs mimic other diseases. Once porphyria is suspected, biochemical analyses easily detect porphyrins and their precursors from blood, urine, or faeces. Mutation screening can be done at the quiescent phase of the disease. Pathogenetic mechanisms and clinical manifestations differ in individual porphyrias and most of them require a specific treatment. Early diagnosis and information about precipitating factors can diminish mortality and prevent subsequent attacks among patients with acute porphyrias, so mutation screening is recommended for family members.

Humans↗
PubMed2006

A novel mutation of POU3F4 causes congenital profound sensorineural hearing loss in a large Chinese family.

OBJECTIVES/HYPOTHESIS: It is known that approximately 5% of congenital profound hearing impaired cases are inherited in X-linked inheritance. This study aimed at identifying its underlying molecular determinant(s) using a large, five-generation Chinese family with multiple familial cases. STUDY DESIGN: Model-based linkage analysis and positional cloning. METHODS: Model-based genetic linkage analyses were performed with the use of microsatellite polymorphisms to determine disease locus. Mutation screening was performed within the family and unrelated population-based controls to establish molecular evidence as to what caused the specific X-linked inheritance pattern in the family. RESULTS: Clinical investigations of the pedigree demonstrated the extremely high penetrance in the male members but no penetrance in the female members. Linkage analyses mapped the disease to the chromosomal region Xq13.I-Xq23 (maximum X-linkage logarithm of odds score = 3.27). Mutation screening of the candidate genes in the linkage region by direct sequencing revealed a de novo missense substitution (925T>C) in the well-known deaf gene. POU3F4. Direct sequencing on 240 unrelated controls did not detect any mutation. CONCLUSIONS: Multiple analysis approaches demonstrated that these disorders in the family were caused by a founder mutation in the POU3F4 gene. Our findings provided confirmatory molecular evidence to support that development of congenital profound sensorineural hearing loss in the Chinese population results from a novel mutation in the same gene.

Adolescent↗
PubMed1999

No evidence of linkage or diabetes-associated mutations in the transcription factors BETA2/NEUROD1 and PAX4 in Type II diabetes in France.

AIMS/HYPOTHESIS: The identification of mutations in hepatocyte nuclear factors-1alpha, -4alpha, -1beta and insulin promoter factor-1 in maturity onset diabetes of the young (MODY) has highlighted the role that transcription factors may have in the development of diabetes. This result has focused molecular genetic studies of diabetes on other transcription factors expressed in the pancreatic beta cell. The basic helix-loop-helix transcription factor BETA2/NEUROD1 (gene symbol, NEUROD1) and the paired box homeodomain transcription factor PAX4 (PAX4) have an important role in islet and beta-cell development. We have examined the contribution of these transcription factors to the development of MODY and late-onset Type II (non-insulin-dependent) diabetes mellitus. METHODS: Linkage studies have been done in MODY families reported to have no mutations in the five known MODY genes and in affected sibling pairs from families with late-onset Type II diabetes. Mutation screening of the coding regions of both genes was also realised by SSCP followed by sequencing in MODY patients and in probands with late-onset Type II diabetes. RESULTS: There was no evidence of linkage with the markers for NEUROD1 and PAX4 either with MODY or late-onset Type II diabetes. Mutation screening showed single nucleotide polymorphisms, several of which resulted in amino acid substitutions: NEUROD1, Ala45Thr; PAX4, Pro321His and Pro334Ala. These amino acid sequence variants were not associated with Type II diabetes. CONCLUSION/INTERPRETATION: Our results indicate that NEUROD1 and PAX4 are not a common cause of either MODY or late-onset Type II diabetes in the French Caucasian population.

Basic Helix-Loop-Helix Proteins↗
PubMed2006

The alpha-chain of high-affinity receptor for IgE (FcepsilonRIalpha) gene polymorphisms and serum IgE levels.

BACKGROUND: The high-affinity receptor for immunoglobulin-E (IgE) (FcepsilonRI) plays a major role in the pathogenesis of allergy, but there are only two published studies on its alpha subunit (FcepsilonRIalpha) genetic variability in allergic diseases. AIMS OF THE STUDY: Mutational screening in the region of the FcepsilonRIalpha gene promoter and the first exon with subsequent genetic variability assessment in allergic patients and a random population sample. METHODS: Allergic subjects were individuals with asthma or urticaria. Age- and sex-matched controls were randomly selected from a large population sample. Mutational screening was performed using a single-stranded conformational polymorphism and subsequent sequencing. Detected polymorphisms were genotyped by restriction fragment length polymorphism. Total serum IgE was measured in allergic subjects and controls. Skin prick tests, blood eosinophil count and aspirin challenge test were performed only in the subjects. A subgroup of the subjects was further characterized by autologous serum skin test, histamine release test, Phadiatop and IgE antibodies against staphylococcal enterotoxins. RESULTS: Two linked polymorphisms -344 C>T and -95 T>C were found within the FcepsilonRIalpha gene. The allele -344 T frequency was 0.45 vs 0.37 (P = 0.33), and the allele -95 C frequency was 0.26 in subjects vs 0.30 in controls (P = 0.62). Serum IgE was significantly higher in subjects homozygous for the -344T allele (TT genotype) than in those carrying the -344 C allele (CT or CC genotype; P = 0.003), but this association was not detectable in controls. CONCLUSIONS: Our findings of genotype-related differences in IgE levels in allergic patients suggest an impact of -344 C>T but not -95 T>C gene polymorphism of FcepsilonRIalpha on total levels of IgE. The genetic variability in FcepsilonRIalpha at the -344 nucleotide of its regulatory sequence, though not related to atopy, predicts higher levels of the immunoglobulin.

Adult↗
PubMed1995

Acute intermittent porphyria in Finland: 19 mutations in the porphobilinogen deaminase gene.

The sensitivity of single-strand conformation polymorphism (SSCP) analysis for the detection of mutations in the porphobilinogen deaminase (PBGD) gene among Finnish patients with acute intermittent porphyria (AIP) was studied. 13 novel mutations including one de novo event, and six previously characterized mutations were identified among AIP patients. The 19 mutations reported here for 28 families cover 72% of all the AIP families in the Finnish population of five million. When compared to direct sequencing, SSCP-analysis detected 17 (89%) of the 19 mutations when a combination of various electrophoretic conditions were used. The most informative electrophoretic condition was a gel run without glycerol in the coldroom (11/18 mutations). 86% of mutations were identified from amplified fragments greater than 300 bp and detection was dependent on both the amount of glycerol in the gel and the running temperature, but seemed to be independent of the size of the analyzed fragment or the type of mutation. The diagnostic efficiency of biochemical assays versus mutation screening in the PBGD gene was studied in three large AIP families, each representing different CRIM subtypes of AIP. The results demonstrated that using assays of erythrocyte PBGD activity, the majority (82%) of family members (n = 51) were diagnosed correctly. Of a total of 81 family members, 30 of whom had deficiency of PBGD confined to non-erythroid tissues, diagnosis at the asymptomatic stage of disease in 11 individuals (14%) required the application of mutation screening.

Alleles↗
PubMed2001

Screening for mutations of the androgen receptor gene in patients with isolated cryptorchidism.

OBJECTIVE: To evaluate the occurrence of mutations of androgen receptor (AR) gene in patients with isolated cryptorchidism. DESIGN: Controlled clinical study. SETTING: Yamagata University Hospital, Yamagata and Tokyo Electric Power Company Hospital, Tokyo, Japan. PATIENT(S): Patients with isolated cryptorchidism (n = 48) and a control group of men with normal phenotype (n = 20). INTERVENTION(S): Blood (lymphocyte DNA). MAIN OUTCOME MEASURE(S): Screening of the AR gene in exons 1-8 using single-strand conformational polymorphism analysis. RESULT(S): No abnormal band patterns were detected in patients with cryptorchidism or in control subjects within the eight exons of the AR gene. CONCLUSION(S): AR gene alterations appear to be an unlikely cause of isolated cryptorchidism.

Adolescent↗
PubMed2000

Phenotypic screening of mutations in Pmr1, the yeast secretory pathway Ca2+/Mn2+-ATPase, reveals residues critical for ion selectivity and transport.

Thirty-five mutations were generated in the yeast secretory pathway/Golgi ion pump, Pmr1, targeting oxygen-containing side chains within the predicted transmembrane segments M4, M5, M6, M7, and M8, likely to be involved in coordination of Ca(2+) and Mn(2+) ions. Mutants were expressed in low copy number in a yeast strain devoid of endogenous Ca(2+) pumps and screened for loss of Ca(2+) and Mn(2+) transport on the basis of hypersensitivity to 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and Mn(2+) toxicity, respectively. Three classes of mutants were found: mutants indistinguishable from wild type (Class 1), mutants indistinguishable from the pmr1 null strain (Class 2), and mutants with differential sensitivity to BAPTA and Mn(2+) toxicity (Class 3). We show that Class 1 mutants retain normal/near normal properties, including (45)Ca transport, Golgi localization, and polypeptide conformation. In contrast, Class 2 mutants lacked any detectable (45)Ca transport; of these, a subset also showed defects in trafficking and protein folding, indicative of structural problems. Two residues identified as Class 2 mutants in this screen, Asn(774) and Asp(778) in M6, also play critical roles in related ion pumps and are therefore likely to be common architectural components of the cation-binding site. Class 3 mutants appear to have altered selectivity for Ca(2+) and Mn(2+) ions, as exemplified by mutant Q783A in M6. These results demonstrate the utility of phenotypic screening in the identification of residues critical for ion transport and selectivity in cation pumps.

ATP-Binding Cassette Transporters↗
PubMed2006

A novel mutation in GJA8 associated with autosomal dominant congenital cataract in a family of Indian origin.

PURPOSE: To identify the genetic defect in an autosomal dominant congenital cataract family, having 15 members in three generations, affected with bilateral cataract that gave the appearance of "full moon" with Y-sutural opacities. METHODS: A detailed family history and clinical data were recorded. A genome-wide scan by two point linkage analysis using nearly 400 microsatellite markers in combination with multipoint lod score and haplotype analysis was carried out. Mutation screening was performed in the candidate gene by bidirectional sequencing of amplified products. RESULTS: A maximum two point lod score of 5.45 at theta=0.00 was obtained with marker D1S534. Haplotype analysis placed the cataract locus to a 14.1 cM region between D1S221 and D1S498, in close proximity to the gene for the gap junction channel protein connexin 50 (GJA8) at 1q21. Mutation screening in GJA8 identified a novel G>C transversion at nucleotide position c.235. This nucleotide change resulted in the substitution of highly conserved valine by leucine at codon 79 (V79L). This nucleotide substitution was neither seen in any unaffected member of the family nor in 180 unrelated control subjects (360 chromosomes) from same ethnic background tested by sequence analysis of GJA8. CONCLUSIONS: The present study describes the mapping of a locus for congenital cataract that appeared like "full moon" with Y-sutural opacities at 1q21 and identifies a previously unreported mutation in GJA8. These findings thus expand the mutation spectrum of GJA8.

Asian People↗
PubMed2006

A screen for mutations in zebrafish that affect myelin gene expression in Schwann cells and oligodendrocytes.

Myelin is the multi-layered glial sheath around axons in the vertebrate nervous system. Myelinating glia develop and function in intimate association with neurons and neuron-glial interactions control much of the life history of these cells. However, many of the factors that regulate key aspects of myelin development and maintenance remain unknown. To discover new molecules that are important for glial development and myelination, we undertook a screen of zebrafish mutants with previously characterized neural defects. We screened for myelin basic protein (mbp) mRNA by in situ hybridization and identified four mutants (neckless, motionless, iguana and doc) that lacked mbp expression in parts of the peripheral and central nervous systems (PNS or CNS), despite the presence of axons. In all four mutants electron microscopy revealed that myelin-forming glia were present and had formed loose wraps around axons but did not form compact myelin. We found that addition of exogenous retinoic acid (RA) rescued mbp expression in neckless mutant embryos, which lack endogenous RA synthesis. Timed application of the RA synthesis inhibitor DEAB to wild type embryos showed that RA signalling is required at least 48 h before the onset of myelin protein synthesis in both CNS and PNS.

Animals↗
PubMed2003

Characterization of the human RAB38 and RAB7 genes: exclusion of new major pathological loci for Japanese OCA.

BACKGROUND: Oculocutaneous albinisms (OCAs) are due to various gene mutations that cause a disruption of melanogenesis in the melanocyte. Four different genes associated with human OCA have been reported, however, not all of OCA patients can be classified according to these four genes. We have sought to find a new major locus for Japanese OCA. Recently two genes, RAB38 and RAB7, were reported to play an important role in melanogenesis in the melanocyte, suggesting that these two genes could be good candidates for new OCA loci. OBJECTIVE: To determine the structures of the human RAB38 and RAB7 genes, and examine if the two genes are new major loci for Japanese OCA. METHODS: We screened mutations in these genes of 25 Japanese OCA patients who lacked mutations in the OCA1 and OCA2 genes with SSCP/heteroduplexes method. RESULTS: We determined the both genes, and their genomic organizations to design the primers for SSCP/heteroduplexes method. And then we screened mutations, but no mutation was detected. CONCLUSION: Neither of the genes is a new major locus for Japanese OCA.

Adolescent↗
PubMed1996

Systematic screening for mutations in the human serotonin-2A (5-HT2A) receptor gene: identification of two naturally occurring receptor variants and association analysis in schizophrenia.

A statistically significant association between a silent mutation (102T/C) in the serotonin-2A (5-HT2A) receptor gene and schizophrenia has recently been reported in a sample of Japanese patients and healthy controls. This finding suggests that genetic predisposition to schizophrenia may be affected by a functional 5-HT2A receptor variant that is in linkage disequilibrium with 102T/C. In the present study, we have sought to identify genetic variation in the 5-HT2A receptor gene by screening genomic DNA samples from 91 unrelated subjects comprising 45 patients with schizophrenia and 46 healthy controls by using single-strand conformation analysis. We have identified four nucleotide sequence variants. Two sequence changes would result in protein alterations: a substitution of threonine by asparagine at position 25 (Thr25Asn), and a substitution of histidine by tyrosine at position 452 (His452Tyr). In order to test for a possible contribution to the development of schizophrenia, we have determined allele frequencies in extended samples of unrelated patients and healthy controls. The two amino acid substitutions are found with similar frequencies in patients and controls, indicating that the presence of these variants is not causally related to the development of schizophrenia. However, the reported association of the non-coding polymorphism 102T/C with the disease has also been detected in our sample (P=0.041, odds ratio=1.28, 95% confidence interval 1.012-1.623).

Alleles↗
PubMed2006

Sutural cataract associated with a mutation in the ferritin light chain gene (FTL) in a family of Indian origin.

PURPOSE: The molecular characterization of 27 members of an Indian family, with 13 members in four generations, affected with Y-sutural congenital cataract. METHODS: Detailed family history and clinical data were collected. A genome-wide scan by two-point linkage analysis using more than 400 microsatellite markers in combination with multipoint lod score and haplotype analysis was performed. Mutation screening was carried out in the candidate gene by bi-directional sequencing of amplified products. RESULTS: A maximum two-point lod score of 6.37 at theta=0.00 was obtained with marker D19S879. Haplotype analysis placed the cataract locus to a 5.0 cM region between D19S902 and D19S867, in close proximity to the L-ferritin light chain gene (FTL) on chromosome 19q13.3. Hematological tests in two affected individuals showed very high levels of serum ferritin without iron overload leading to the diagnosis of hyperferritinemia-cataract syndrome. Mutation screening in FTL identified a G>A change at position 32 (c.-168G>A) in a highly conserved 3 nucleotide motif that forms a loop structure in the iron responsive element (IRE) in the 5'-untranslated region (5'-UTR). This nucleotide alteration was neither seen in any unaffected member of the family nor found in 50 unrelated control subjects. CONCLUSIONS: The present study is the first report of a Y-sutural congenital cataract mapping to 19q13.3. The mutation observed in FTL in this family highlights the phenotypic heterogeneity of the disorder in relation to the genotype as the identical mutation (32 G>A) has previously been reported in two Italian families with entirely different phenotypes. It is also the first report of hereditary hyperferritinemia-cataract syndrome in a family of Indian origin.

5' Untranslated Regions↗
PubMed2004

Refining the Amsterdam Criteria and Bethesda Guidelines: testing algorithms for the prediction of mismatch repair mutation status in the familial cancer clinic.

PURPOSE: Hereditary nonpolyposis colon cancer (HNPCC) is a Mendelian dominant syndrome of bowel, endometrial, and other cancers and results from germline mutations in mismatch repair (MMR) genes. HNPCC is now best diagnosed on molecular grounds using MMR mutation screening, aided by microsatellite instability (MSI) and immunohistochemistry in tumors. Selection of families for molecular investigation of HNPCC is usually based on suboptimal methods (Amsterdam Criteria or Bethesda Guidelines), but these can be improved using additional clinical data (mean ages of affected persons and presence of endometrial cancer) in a quantitative model. METHODS: We have verified the performance of the Wijnen model and have shown that it remains valid when HNPCC is diagnosed using mutation screening, MSI, and immunohistochemistry. We have also set up and verified our own models (Amsterdam-plus and Alternative), which perform at least as well as the Wijnen model. RESULTS: The Amsterdam-plus model improves on the Amsterdam Criteria by using five extra variables (numbers of colorectal and endometrial cancers in the family, number of patients with five or more adenomas, number with more than one primary cancer of the colorectum or endometrium, and mean age of presentation) and performs better than the Wijnen model. The Alternative model avoids the need to evaluate the Amsterdam Criteria and performs nearly as well as the other models. CONCLUSION: We believe that a quantitative model, such as the Amsterdam-plus model, should be the first choice for selecting families or patients for evaluation of HNPCC using molecular tests. We present an algorithm for this process.

Adult↗