SEARCH · PubMed Health

Results for “Exons”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

PubMed1999

Detection of two novel mutations (nt2762, exon 2, CAG to TAG, and nt2483 or 2484, exon 2, +A) in individuals with congenital type I antithrombin deficiencies.

Genetic analyses were performed on two Japanese kindreds with congenital type I antithrombin deficiency causing recurrent thrombosis. The seven exons and flanking intron regions of the antithrombin gene were amplified by polymerase chain reaction followed by direct nucleotide sequencing. In case 1, one novel nonsense mutation, CAG to TAG at codon 100, nucleotide 2762, in exon 2, was detected. In case 2, one novel minor insertion, AT to AAT at codon 7, nucleotide 2483 or 2484, in exon 2, was detected, leading to a frameshift which resulted in a stop codon TGA at codon 32.

Adolescent↗

PubMed1998

HLA-C high resolution typing: analysis of exons 2 and 3 by sequence based typing and detection of polymorphisms in exons 1-5 by sequence specific primers.

HLA-C high resolution sequence based typing developed in this study involves a unique DNA amplification encompassing exon 1 to intron 3 and four fluorescent sequencing reactions covering exon 2 and 3. Both dye primer and dye terminator sequencing techniques were performed and results compared. This approach allowed the identification of all of the 50 HLA-C allelic variants so far described, except for two allele pairs that are distinguished by non-coding nucleotide changes (Cw*12021 = 12022, Cw*15051 = 15052) and three allele pairs (Cw*0701 = 706, Cw*1701 = 1702 and Cw*1801 = 1802) that share the same nucleotide sequence in exon 2 and 3. For complete subtyping of these allelic variants, an amplification based on sequence specific primers (PCR-SSP) was used. No ambiguous heterozygous combinations of alleles were detected in our panel so far. HLA-C typing data obtained by this method were compared with data from serological and low resolution PCR-SSP typing, which had been performed previously on the samples sequenced.

Base Sequence↗

PubMed1999

Mutations in the exons and exon-intron junction regions of human cytochrome P-4502E1 gene and alcoholism.

Cytochrome P-4502E1 (CYP2E1) is a major component of the microsomal ethanol-oxidizing system (MEOS) and is also involved in the metabolism of a variety of foreign compounds, including carcinogens. It has been shown that there are interindividual variations in the expression of human CYP2E1. Gene-environmental interactions have been suggested to account for the difference. In this study, we screened nine exons and exon-intron junctions of the human CYP2E1 gene for detecting allelic variants in genomic DNA samples obtained from 115 Japanese controls, 96 alcoholics, and 44 patients with alcoholic liver diseases. A novel missense mutation in exon 2 (V72L) was found in Japanese controls, but the frequency was low (2.6%). In addition, two novel silent mutations (T303T and F420F), together with one mutation in intron 2, were found. However, no association of these mutations with alcoholism and alcoholic liver diseases was found. Our data indicate that nucleotide replacement in the open reading frame of CYP2E1 gene is not a major factor for interindividual differences in expression of CYP2E1 and susceptibility to alcohol-related disorders.

Alcoholism↗

PubMed1996

Selection of the bovine papillomavirus type 1 nucleotide 3225 3' splice site is regulated through an exonic splicing enhancer and its juxtaposed exonic splicing suppressor.

Alternative splicing is an important mechanism for the regulation of bovine papillomavirus type 1 (BPV-1) gene expression during the virus life cycle. However, one 3' splice site, located at nucleotide (nt) 3225, is used for the processing of most BPV-1 pre-mRNAs in BPV-1-transformed C127 cells and at early to intermediate times in productively infected warts. At late stages of the viral life cycle, an alternative 3' splice site at nt 3605 is used for the processing of the late pre-mRNA. In this study, we used in vitro splicing in HeLa cell nuclear extracts to identify cis elements which regulate BPV-1 3' splice site selection. Two purine-rich exonic splicing enhancers were identified downstream of nt 3225. These sequences, designated SE1 (nt 3256 to 3305) and SE2 (nt 3477 to 3526), were shown to strongly stimulate the splicing of a chimeric Drosophila doublesex pre-mRNA, which contains a weak 3' splice site. A BPV-1 late pre-mRNA containing the nt 3225 3' splice site but lacking both SE1 and SE2 was spliced poorly, indicating that this 3' splice site is inherently weak. Analysis of the 3' splice site suggested that this feature is due to both a nonconsensus branch point sequence and a suboptimal polypyrimidine tract. Addition of SE1 to the late pre-mRNA dramatically stimulated splicing, indicating that SE1 also functions as an exonic splicing enhancer in its normal context. However, a late pre-mRNA containing both SE1 and SE2 as well as the sequence in between was spliced inefficiently. Further mapping studies demonstrated that a 48-nt pyrimidine-rich region immediately downstream of SE1 was responsible for this suppression of splicing. Thus, these data suggest that selection of the BPV-1 nt 3225 3' splice site is regulated by both positive and negative exonic sequences.

Animals↗

PubMed1999

Alternative splicing of exon 17 and a missense mutation in exon 20 of the insulin receptor gene in two brothers with a novel syndrome of insulin resistance (congenital fiber-type disproportion myopathy).

The insulin receptor (IR) in two brothers with a rare syndrome of congenital muscle fiber type disproportion myopathy (CFTDM) associated with diabetes and severe insulin resistance was studied. By direct sequencing of Epstein-Barr virus-transformed lymphocytes both patients were found to be compound heterozygotes for mutations in the IR gene. The maternal allele was alternatively spliced in exon 17 due to a point mutation in the -1 donor splice site of the exon. The abnormal skipping of exon 17 shifts the amino acid reading frame and leads to a truncated IR, missing the entire tyrosine kinase domain. In the correct spliced variant, the point mutation is silent and results in a normally translated IR. The paternal allele carries a missense mutation in the tyrosine kinase domain. All three cDNA variants were present in the lymphocytes of the patients. Purified IR from 293 cells overexpressing either of the two mutated receptors lacked basal or stimulated IR beta-subunit autophosphorylation. A third brother who inherited both normal alleles has an normal muscle phenotype and insulin sensitivity, suggesting a direct linkage of these IR mutations with the CFTDM phenotype.

Adolescent↗

PubMed2002

Severe coagulation factor V deficiency caused by 2 novel frameshift mutations: 2952delT in exon 13 and 5493insG in exon 16 of factor 5 gene.

A male infant with severe bleeding tendency had undetectable factor V activity. Sequence analysis of the proband's DNA revealed one base deletion in exon 13 (2952delT) and one base insertion in exon 16 (5493insG) in heterozygous form. Both mutations introduced a frameshift and a premature stop at codons 930 and 1776, respectively. The proband's father and mother were heterozygous for 2952delT and for 5493insG, respectively. Both mutations would result in the synthesis of truncated proteins lacking complete light chain or its C-terminal part. In the patient's plasma, no factor V light chain was detected by enzyme-linked immunosorbent assay. The N-terminal portion of factor V containing the heavy chain, and the connecting B domain was severely reduced but detectable (1.7%). A small amount of truncated factor V-specific protein with a molecular weight ratio of 236 kd could be immunoprecipitated from the plasma and detected by Western blotting. This protein, factor V(Debrecen), corresponds to the translated product of exon 16 mutant allele.

Codon, Nonsense↗

PubMed2000

A compound heterozygote for a novel missense mutation (G105R) in exon 3 and a missense mutation (D204E) in exon 5 of the lipoprotein lipase gene in a Japanese infant with hyperchylomicronaemia.

We systematically investigated the molecular defects resulting in primary lipoprotein lipase (LPL) deficiency in a Japanese male infant (hereafter called 'the patient') with severe fasting hypertriglyceridaemia (type I hyperlipoproteinaemia). The primary LPL deficiency was diagnosed on the basis of the findings that no LPL activity was detected in post-heparin plasma (PHP) and that the immunoreactive LPL mass in PHP was less than 2% of the control level. The patient was a compound heterozygote for a novel missense mutation (G(568)GA-->AGA/Gly(105)-->Arg; G105R) in exon 3 and a missense mutation (GAC(867)-->GAG/Asp(204)-->Glu; D204E) in exon 5 of the LPL gene. The biological significance of both missense mutations was examined by an in vitro study of the expression of the mutant G105R LPL cDNA and D204E LPL cDNA in COS-1 cells. Both mutant LPLs were catalytically inactive and were barely released by heparin from the expressing COS-1 cells. These findings explain the failure to detect LPL activity and immunoreactive LPL mass in the patient's PHP. The G105R allele could be detected by digestion with the BsmAI restriction enzyme, and the D204E allele by digestion with HincII. The patient inherited the G105R allele from his mother and the D204E allele from his father. His parents were heterozygotes for the corresponding mutant allele, but normolipidaemic. The novel G105R missense mutation could not be detected by conventional analysis of single-strand conformation polymorphism, but it was identified by extensive sequencing of the entire exons and their flanking regions in the LPL gene.

Alleles↗

PubMed2004

ASA E382K disrupts a potential exonic splicing enhancer and causes exon skipping, but missense mutations in ASA are not associated with ESEs.

Metachromatic leukodystrophy (MLD) is an autosomal recessive disorder caused by mutations in the arylsulfatase A (ASA) gene. We identified a Thai boy with typical late-infantile MLD and found that he was a compound heterozygote for a novel mutation, g.IVS3-2A>G causing c.679-696del inherited from his father, and a previously reported missense mutation, g.1144G>A causing c.1102-1204del inherited from his mother. The g.1144G>A mutation was located in the middle of exon 7 and previously assumed to be deleterious by causing an amino acid change, E382K. We, herein, found that its actual pathogenic effect was splicing-related by disrupting a potential exonic splicing enhancer (ESE) and causing a complete exon 7 skipping. This is the first missense mutation in the ASA gene that is deleterious from disrupting a potential ESE. The results prompted us to investigate pathogenic effects of other reported missense mutations in the ASA gene. Unlike pathogenic missense mutations in some other genes, those in the ASA gene do not colocalize with ESE sites suggesting that pathogenic effects of majority of them are not splicing-related.

Alternative Splicing↗

PubMed2005

Exon skipping partially restores factor VIII coagulant activity in patients with mild hemophilia A with exon 13 duplication.

Ectopic mRNA was analyzed by reverse transcriptase polymerase chain reaction (RT-PCR) in patients with duplication of F8 gene exon 13, a mutation which has been demonstrated to be a cause of mild hemophilia A in 32% of Northern Italian subjects. Two different transcripts originate from mutated genomic DNA, due to alternative splice processes. The larger-sized transcript contains both duplicated exons 13, the smaller one contains only one exon 13. The residual FVIII:C activity which accounts for the mild hemophilia A phenotype derives from the latter transcript.

Alternative Splicing↗

PubMed1988

A 19-base pair deletion in the pro-alpha 2(I) gene of type I procollagen that causes in-frame RNA splicing from exon 10 to exon 12 in a proband with atypical osteogenesis imperfecta and in his asymptomatic mother.

Previous observations established that fibroblasts from a proband with atypical osteogenesis imperfecta synthesized about equal amounts of normal pro-alpha 2(I) chains and shortened pro-alpha 2(I) chains of type I procollagen. The pro-alpha 2(I) chains were shortened because of an in-frame deletion of most or all of the 18 amino acids encoded by exon 11 of the pro-alpha 2(I) gene. Here it was demonstrated that one of the proband's alleles for the pro-alpha 2(I) gene contained a 19-base pair deletion at the junction of intervening sequence 10 and exon 11 that produced an RNA splicing defect. Probe protection experiments did not reveal any evidence for use of cryptic splice sites, and they suggested that the major species of abnormally spliced pro-alpha 2(I) mRNA in the proband's fibroblasts was completely spliced from exon 10 to 12. The defect in RNA splicing is unusual among RNA-splicing mutations in producing an abnormal polypeptide chain that is used for protomer assembly. Since the probe protection experiments showed the same defect in the mRNA from the fibroblasts of the asymptomatic mother, the mutation was inherited in an autosomal dominant manner but showed variable phenotypic expression in the proband's family.

Base Sequence↗

PubMed1995

Exon redefinition by a point mutation within exon 5 of the glucose-6-phosphatase gene is the major cause of glycogen storage disease type 1a in Japan.

Glycogen storage disease (GSD) type 1a (von Gierke disease) is an autosomal recessive disorder caused by a deficiency in microsomal glucose-6-phosphatase (G6Pase). We have identified a novel mutation in the G6Pase gene of a individual with GSD type 1a. The cDNA from the patient's liver revealed a 91-nt deletion in exon 5. The genomic DNA from the patient's white blood cells revealed no deletion or mutation at the splicing junction of intron 4 and exon 5. The 3' splicing occurred 91 bp from the 5' site of exon 5 (at position 732 in the coding region), causing a substitution of a single nucleotide (G to T) at position 727 in the coding region. Further confirmation of the missplicing was obtained by transient expression of allelic minigene constructs into animal cells. Another eight unrelated families of nine Japanese patients were all found to have this mutation. This mutation is a new type of splicing mutation in the G6Pase gene, and 91% of patients and carriers suffering from GSD1a in Japan are detectable with this splicing mutation.

Adult↗

PubMed1994

The hybrid rat cytochrome P450 containing the first 5 exons of the CYP11B1 and last 4 exons from the CYP11B2 enzyme retains 11 beta-hydroxylase activity, but the alternative hybrid is inactive.

Human, mouse and rats have 2 different cytochrome P-450 11 beta-hydroxylases in the adrenal cortex. The classical rat 11 beta-hydroxylase or CYP11B1 enzyme hydroxylates deoxycorticosterone to corticosterone and 18-hydroxydeoxycorticosterone and is located throughout the adrenal. The second aldosterone synthase or CYP11B2 enzyme is located in the zona glomerulosa and converts deoxycorticosterone to corticosterone, 18-hydroxycorticosterone and aldosterone. In rat the coding nucleotide sequence and the deduced amino acid sequences of the CYP11B1 and CYP11B2 genes are homologous by 88% and 83%, respectively. We have constructed two different hybrid cDNAs by exchanging two fragments of the rat CYP11B1 and CYP11B2 at the junction of the 5/6 exon and expressed them in COS 7 cells. The hybrid CYPH11B1 construct containing the first 5 exons of the CYP11B1 when expressed, retains 11 beta-hydroxylase activity, but cannot process corticosterone to 18-hydroxycorticosterone or aldosterone. The hybrid CYPH11B2 construct containing the first 5 exons of the CYP11B2 enzyme when expressed is inactive.

Animals↗

PubMed1982

Exon cloning: immunoenzymatic identification of exons of the chicken lysozyme gene.

A 10-kilobase DNA fragment containing exons 1 and 2 of the chicken lysozyme gene has been randomly cleaved with DNase I. After tailing and cloning into the plasmid pUK230, Lac+ colonies were selected. Colonies harboring expressed fragments of the exons could be detected by an immunoenzymatic assay using antibodies against lysozyme. The smallest fragment coded for 10 amino acids and the largest coded for almost all residues of exon 2. These results suggest that any gene of any genome cloned in this way can be detected if antibodies against the gene product are available.

Animals↗

PubMed1997

Exon-by-exon screening for RB germline mutations using Heteroduplex-SSCP analysis.

OBJECTIVE: To disclose the nature of RB1 germline mutations in Chinese and to develop a practical and effective way for mutational screening. METHODS: Leukocyte DNA was prepared from 8 Chinese patients with hereditary retinoblastoma. PCR combined with nonisotopic heteroduplex-SSCP analysis was used to screen leukocyte DNA for RB1 germline mutations, exon-by-exon, without the use of restriction endonuclease digestion. The mutations were finally identified by sequencing. In order to testify the effectiveness of this method, the same method was used to detect other 17 samples which have been previously analyzed by other methods. RESULTS: Heterozygous germline mutations were detected in the leukocyte DNA of 6 out of 8 Chinese patients: G del/codon 46, T del/codon 131, CAGAA del/codon 257-258, GCAgta-->GCAgca/donor of exon 16, C-->T/codon 661, and C-->T/codon 787. Heteroduplex-SSCP analysis may detect RB1 germline mutations in 68% (17/25) unselected patients, which is more effective than SSCP(56%) or heteroduplex analysis(64%) alone. The corrected RB1 mutation detection rate may be 80% if the samples were previously analyzed by Southern blotting, which is much higher than those reported on literature. CONCLUSION: Mutations involving a few base pairs in RB1 gene are common in Chinese. Heteroduplex-SSCP analysis is more useful and effective than SSCP or heteroduplex analysis alone for the rapid screening for unknown mutations.

Female↗

PubMed1994

Absence of hereditary mutations in exons 5 through 9 of the p53 gene and exon 24 of the neurofibromin gene in families with glioma.

Inherited mutations of the p53 and neurofibromin genes are thought to cause two distinct neoplastic disorders in which gliomas occur, the Li-Fraumeni syndrome and neurofibromatosis type 1. We investigated the possibility that inherited mutations in specific regions of these genes also contributed to the clustering of gliomas in otherwise normal families. Twenty-six members of 16 families with glioma were screened for germline mutations of exons 5 through 9 of the p53 gene and exon 24 of the neurofibromin gene using a polymerase chain reaction-single-strand conformation polymorphism method. No germline mutations were found, suggesting that the genetic basis of familial glioma is distinct from that of gliomas occurring in the Li-Fraumeni syndrome, and that inherited mutations of the catalytic domain of neurofibromin do not predispose affected glioma families to these tumors.

Adult↗

PubMed2004

PTCH polymorphism is associated with the rate of increase in basal cell carcinoma numbers during follow-up: preliminary data on the influence of an exon 12-exon 23 haplotype.

After first presentation with a basal cell carcinoma (BCC), patients demonstrate interindividual diversity in the rate of development of further BCCs (number/year of follow-up). The mechanism for this variation is unknown. In this study, we evaluated whether PTCH variants mediate this phenomenon. We used negative binomial regression analysis to identify associations between BCC numbers/year and host characteristics, parameters of exposure to ultraviolet radiation (UVR), and PTCH exon 12(1686) C/T, intron 15(2560+9) G/C, and exon 23(3944) C/T genotypes and haplotypes in 279 BCC cases who presented with an initial tumor on the head/neck. PTCH genotypes were not significantly associated with BCCs/year, although cases with two copies of the C1686-C3944 haplotype developed significantly fewer BCCs/year than those without this haplotype (rate ratio = 0.44; 95% CI = 0.27-0.71). Cases with one copy of T1686-T3944 developed more BCCs/year (rate ratio = 2.46; 95% CI = 1.27-3.97) than those without the haplotype. We found no significant associations between BCCs/year and the other PTCH haplotypes studied. We reexamined the association of C1686-C3944 with BCCs/year in a model that included UVR exposure parameters (sunburning in childhood, sunbathing score, intermittency of exposure between 40 and 60 years of age, exposure in hours/year) and skin type, gender, and age at first presentation. The association between C1686-C3944 and BCCs/year remained significant (rate ratio = 0.44; 95% CI = 0.26-0.73 for two copies of the haplotype). The data show that allelic variation in PTCH contributes to the rate of development of BCC.

Adult↗

PubMed2006

ALys amyloidosis caused by compound heterozygosity in exon 2 (Thr70Asn) and exon 4 (Trp112Arg) of the lysozyme gene.

Hereditary amyloidoses are caused by germline mutations, which increase the propensity of a protein to form cross-beta aggregates and deposit as amyloid. Hereditary amyloidoses are particularly interesting as they help to understand how changes in the primary structure of an otherwise non-amyloidogenic protein contribute to amyloidogenesis. Here we report on a novel form of systemic ALys amyloidosis, caused by compound heterozygosity in exon 2 (p.T70N) and exon 4 (p.W112R) of the lysozyme gene (LYZ), with both mutations being present on the same allele. This type of hereditary ALys amyloidosis is characterized by extended amyloid deposits in the upper gastrointestinal tract, entire colon, and kidney, leading to gastrointestinal bleeding. Both mutations are probably effective in disease manifestation. The novel mutation at position 112 in the mature protein is located within the alpha-helical domain of the protein and therefore outside the cluster of residues that has so far been implicated in ALys amyloidosis. Taken together with the p.T70N mutation, this results in a lysozyme species where the correct folding of various protein domains is probably impaired and increases the propensity of amyloid fibril formation. Interestingly, this form of ALys amyloidosis is also characterized by the occurrence of proteolytic fragments of lysozyme in the amyloid deposits.

Adult↗

PubMed1992

Human beta-globin mRNAs that harbor a nonsense codon are degraded in murine erythroid tissues to intermediates lacking regions of exon I or exons I and II that have a cap-like structure at the 5' termini.

Previous studies have demonstrated that nonsense codons within beta zero-thalassemic or in vitro-mutagenized human beta-globin transgenes result in the production of mRNAs that are degraded abnormally rapidly in the cytoplasm of murine erythroid cells. As a consequence, three RNA degradative intermediates are formed that lack sequences from either exon I or exons I and II. We show here that the intermediates, like the full-length mRNA from which they derive and the endogenous murine beta maj-globin mRNA, bind to the anticap monoclonal antibody H-20 in a way that is competed by the cap analogue m7G and eliminated by prior exposure to tobacco acid pyrophosphatase. Furthermore, the intermediates, like the two full-length mRNAs, are resistant to a 5'----3' exonuclease activity isolated from HeLa cell nuclei that degrades uncapped but not capped ribopolymers. Based on these observations, the intermediates appear to possess a structure that is indistinguishable from the cap at the 5' end of mRNA, i.e. a methylated nucleoside that is linked to the RNA by a 5'-5' phosphodiester bond. Detection of the intermediates during murine development was concomitant with detection of full-length thalassemic mRNA. Intermediate production appears to be influenced by RNA structure as indicated by the products that derive from a beta zero-thalassemic beta-globin transgene harboring a structural alteration (a 4 bp deletion) that was larger than any of those previously studied.

Animals↗