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Frameshift mutations at mononucleotide repeats in caspase-5 and other target genes in endometrial and gastrointestinal cancer of the microsatellite mutator phenotype.

The majority of tumors from hereditary nonpolyposis colorectal cancer families and a subset of unselected gastrointestinal and endometrial tumors exhibit a microsatellite mutator phenotype (MMP) that leads to the accumulation of hundreds of thousands of clonal mutations in simple repeat sequences. The mutated genes with positive or negative roles in cell growth or survival in aneuploid gastrointestinal cancer (e.g., APC, K-ras, and p53) are less frequently mutated in near-diploid MMP gastrointestinal tumors. These tumors accumulate mutations in other genes, such as DNA mismatch repair hMSH3 and hMSH6, transforming growth factor-beta type II receptor, and BAX. All these genes carry, within their coding sequences, mononucleotide repeats that are preferred targets for the MMP. Endometrial carcinoma is the most common type of extracolonic neoplasia in the hereditary nonpolyposis colorectal cancer syndrome, but the spectrum of its target cancer genes is not well characterized. Here, we report that endometrial cancer of the MMP also accumulates mutations in genes that are typically mutated in gastrointestinal cancer of the mutator pathway, including BAX (55%), hMSH3 (28%), and hMSH6 (17%). We also report the detection of frameshift mutations in caspase-5, a member of the caspase family of proteases that has an (A)10 repeat within its coding region, in MMP tumors of the endometrium, colon, and stomach (28, 62, and 44%, respectively). We therefore suggest caspase-5 as a new target gene in the microsatellite mutator pathway for cancer.

Caspases↗

CHK1 frameshift mutations in genetically unstable colorectal and endometrial cancers.

The protein encoded by the CHK1 gene plays an important role in the G2 checkpoint in mammalian cells. In its coding region it presents a sequence of nine consecutive adenines that are a potential site of mutations in tumors with microsatellite instability (MSI). We analyzed the presence of frameshift mutations in the CHK1 gene in human colon and endometrial cancer samples. In the same cancer samples genes known to be altered in these tumors (BAX, TGFBRII, and IGFIIR) were also analyzed. CHK1 frameshfit mutations were found in 1 out 10 colon cancers and 2 out of 7 endometrial cancers showing MSI. CHK1 alterations were associated with the presence of a high degree of MSI. No alterations were found in patients with tumors showing low frequency or lacking instability (microsatellite stable). The same was true for the other four genes analyzed. The insertion or deletion of one A in the poly A tract resulted in a truncated protein. Alterations of the CHK1 gene could represent an alternative way of cancer cells to escape from cell cycle control. Genes Chromosomes Cancer 26:176-180, 1999.

Biomarkers, Tumor↗

A novel PAX6 frameshift mutation in a kindred from Atlantic Canada with familial aniridia.

BACKGROUND: Many mutations in PAX6, a member of a family of genes essential for normal development, have been described. We carried out a study to identify the mutation in PAX6 responsible for aniridia, an autosomal dominant disorder, in a kindred from Atlantic Canada. METHODS: Polymerase chain reaction amplification of coding exons, single-strand conformation polymorphism analysis and DNA sequencing. RESULTS: A novel deletion of an adenosine residue at position 1030 (1030delA) was detected. INTERPRETATION: The mutation responsible for aniridia in this kindred is expected to cause a frameshift in the PAX6 coding sequence and truncation of the homeodomain, which is essential for the function of the pax6 protein.

Adult↗

Selection against frameshift mutations limits microsatellite expansion in coding DNA.

Microsatellite enrichment is an excess of repetitive sequences characteristic to all studied eukaryotes. It is thought to result from the accumulated effects of replication slippage mutations. Enrichment is commonly measured as the ratio of the observed frequency of microsatellites to the frequency expected to result from random association of nucleotides. We have compared enrichment of specific types of microsatellites in coding sequences with those in noncoding sequences across seven eukaryotic clades. The results reveal consistent differences between coding and noncoding regions, in terms of both the quantity of repetitive DNA and the types present. In noncoding regions, all types of microsatellite (mono-, di-, tri-, tetra-, penta-, and hexanucleotide repeats) are found in excess, and in all cases, these excesses scale in a similar exponential fashion with the length of the microsatellite. This suggests that all types of noncoding repeats are subject to similar mutational and selective processes. Coding repeats, however, appear to be under much stronger and more specific constraints. Tri- and hexanucleotide repeats are found in consistent and significant excess over a wide range of lengths in both coding and noncoding sequences, but other repeat types are much less frequent in coding regions than in noncoding regions. These findings suggest that the differences between coding and noncoding microsatellite frequencies arise from specific selection against frameshift mutations in coding regions resulting from length changes in nontriplet repeats. Furthermore, the excesses of tri- and hexanucleotide coding repeats appear to be controlled primarily by mutation pressure.

Animals↗

Microsatellite instability and frameshift mutations in genes involved in cell cycle progression or apoptosis in ovarian cancer.

The loss of mismatch repair enzymes increases the mutation rate in microsatellites and coding regions of the genome and appears to be involved in drug resistance. The replication error (RER+) phenotype, associated with microsatellite instability, has been widely described for both familial and sporadic colon cancers and for gastric and endometrial tumors. For ovarian cancer, the incidence of RER+ cases among sporadic tumors is still uncertain. We analyzed epithelial ovarian tumors and ovarian carcinoma cell lines for microsatellite instability and for mutations in the coding regions of different genes, including the recently discovered human CHK-1 gene, which has an important role in controlling cell cycle progression and whose coding region contains a poly(A)9 tract. Microsatellite instability and frameshift mutations in coding regions of BAX, TGFbetaRII, IGFIIR, E2F-4, ICE, and CHK-1 genes were analyzed in ovarian cancer samples and cell lines by polymerase chain reaction (PCR). Approximately 26% of patients showed microsatellite instability in two or more loci. BAT-26 locus showed no alteration in primary tumors. We detected a BAX mutation in one tumor sample and a TGFbetaRII mutation in one cell line. Our findings confirm the presence of the RER+ phenotype in sporadic ovarian cancer. The low rate of mutation in genes previously reported to be altered in colon and gastric cancer suggests that other not yet identified genes might be altered and could play a role in tumor progression and response to treatment in RER+ ovarian tumors.

Adult↗

Triose phosphate isomerase deficiency in 3 French families: two novel null alleles, a frameshift mutation (TPI Alfortville) and an alteration in the initiation codon (TPI Paris).

Three French families with triose phosphate isomerase (TPI) deficiency were studied, and 2 new mutations giving rise to null alleles were observed: a frameshift mutation with deletion of the 86-87 TG dinucleotide in codon 29 (TPI Alfortville) and a T-->A transversion in nucleotide 2 of the initiation codon (TPI Paris). The first mutation occurred in compound heterozygosity with the frequent E105D mutation. The second mutation occurred in association with the 2-nucleotide promoter variant (-43G,-46A). In a third family, the propositus was an E105D homozygote. In the TPI Paris family, the coinheritance of the -43,-46 promoter variant appeared to exert little, if any, effect on TPI enzyme activity, a finding consistent with 2 previous reports that questioned the putative role of the promoter polymorphism as a true deficiency variant. Similarly, the further coinheritance of glucose-6-phosphate dehydrogenase (G6PD) A- (202 G-->A/376 A-->G) appeared to have little effect on the observed phenotype. Compound heterozygosity for the E105D mutation with the null allele TPI Alfortville appeared to lead to a more severe clinical syndrome than did E105D homozygosity, suggesting that compound heterozygosity with null alleles may lead to more profound clinical abnormalities than homozygosity with missense alleles. A simple, rapid polymerase chain reaction and restriction enzyme procedure for the E105D mutation was developed for prenatal diagnosis in one family and subsequently used for screening in the other families.

Adult↗

A case of Japanese cleidocranial dysplasia with a CBFA1 frameshift mutation.

Cleidocranial dysplasia (CCD), which is caused by mutations of the core binding factor alpha 1 (CBFA1)/runt-related gene 2 (Runx2), is an autosomal, dominantly inherited disorder of high penetrance affecting skeletal ossification and tooth development. Recently, we found a novel frameshift mutation 383-T-insertion (S128F) in exon 3 in the CBFA1 gene of a Japanese classic CCD patient. We describe our detailed investigation of the patient with CCD associated with the CBFA1 mutation. The patient showed the characteristic expression of CCD, such as dysplasia of the clavicles, patent fontanelles, short stature, impacted supernumerary teeth, and delayed eruption of the permanent teeth. In addition to these characteristics, orthopantomography delayed ossification of the mandibular symphysis and a three-dimensional computed tomograph (3D-CT) analysis showed hypoplasia of the zygomatic arch. Furthermore, the acellular cementum of an impacted supernumerary tooth was absent in this patient. Thus, the CBFA1 mutation was critical for the pathogenesis of CCD in this patient.

Amino Acid Sequence↗

Instabilotyping: comprehensive identification of frameshift mutations caused by coding region microsatellite instability.

Coding region frameshift mutation caused by microsatellite instability (MSI) is one mechanism contributing to tumorigenesis in cancers with MSI in high frequency. Mutation of TGFBR2 is one example of this process. To identify additional examples, a large-scale genomic screen of coding region microsatellites was conducted. 1115 coding homopolymeric loci with six or more nucleotides were identified in an online genetic database. Mutational screening was performed at 152 of these loci in 46 colorectal tumors with MSI in high frequency. Nine loci were mutated in > or =20% of tumors, 10 loci in 10-20%, 24 loci in 5-10%, 43 loci in <5%, and 66 loci were not mutated in any tumors. The most frequently mutated novel loci were the activin type II receptor gene (58.1%), SEC63 (48.8%), AIM 2 (47.6%), a gene encoding a subunit of the NADH-ubiquinone oxidoreductase complex (27.9%), a homologue of mouse cordon-bleu (23.8%), and EBP1/PA2G4 (20.9%). This genome-wide approach identifies coding region MSI in genes or pathways not implicated previously in colorectal tumorigenesis, which may merit functional study or other additional analysis.

3' Untranslated Regions↗

[Translational frameshift may be occur in p11, an interaction protein of Cx31, in yeast].

Connexin 31 is a member of connexin family. The carboxy-terminal cytosolic domain of connexin 31 contains several potential phosphorylation sites. In this work, a yeast two-hybrid protein interaction screen have been used to identify proteins that bind to the carboxy-terminus of connexin 31, and the p11 protein, an unique member of S100 protein family, and one of the two subunits of the annexin II tetramer was isolated. Interestingly, from yeast two-hybrid AD's coding sequence, three different reading frames of p11 DNA sequence were found,which come from different AD plasmids. By constructing AD plasmids using p11 ORF or 5' UTR, the protein coding by p11 ORF bind to connexin 31, while polypeptides coding by three kinds of 5 UTR did not bind to connexin 31, suggesting a translational frameshift of p11 fusion protein. To construct baits by dividing connexin 31 C-terminus into two domain, the p11 binding domain of connexin 31 was found located between 206-237 codons. The plasmid Cx31CT-pGEX-4T-2 was constructed for expression and purification of GST-Cx31CT; and p11-pQE30 for expression and purification of 6xHis-p11. In vitro binding assay showed that recombinant Cx31 interacted with recombinant p11.

5' Untranslated Regions↗

T-cell factor-4 frameshift mutations occur frequently in human microsatellite instability-high colorectal carcinomas but do not contribute to carcinogenesis.

Colorectal carcinomas with microsatellite instability accumulate errors in short repetitive DNA repeats, especially mono and dinucleotide repeats. One such error-prone A(9) monorepeat is found in exon 17 of the TCF-4 gene. TCF-4 and beta-catenin form a transcription complex, which is important for both maintenance of normal epithelium and development of colorectal tumors. To elucidate the relevance of frameshift mutations in the TCF-4 in colorectal carcinogenesis, a variety of investigations in human tumors and cell lines was performed. It was found that mutations in the TCF-4 A(9) repeat do not contribute to tumorigenesis and seem to be passenger mutations.

Colorectal Neoplasms↗

Genetic analysis of oculocutaneous albinism type 1 (OCA1) in Indian families: two novel frameshift mutations in the TYR Gene.

PURPOSE: Oculocutaneous albinism type 1 (OCA1) patients demonstrate a partial or total lack of melanin in the skin, hair and eye. OCA1 is an autosomal recessive genetic disorder caused by mutations in the TYR gene located at chromosome band 11q14-q25. The purpose of this study was to carry out genetic analysis of OCA1 in Indian families. METHODS: Genomic DNA was isolated from blood leukocytes of all the individuals in this study. Haplotype analysis was performed at the TYR locus using informative microsatellite markers. Eight sets of primers were used to amplify the entire coding region of the TYR gene for bidirectional direct sequencing mutation analysis. RESULTS: Two novel deletions (c.937del8, c.1379del2) and a previously known nonsense mutation (R278X) in the TYR gene were identified from a total of 8 oculocutaneous albinism patients in India. CONCLUSIONS: Our study reports the distribution of two novel frameshift and a previously reported nonsense mutations in four OCA1 families from the Indian population. These findings will contribute to the development of a diagnostic method for OCA1 carrier status and genetic counseling for OCA1 affected families.

Albinism, Oculocutaneous↗

Identification of a novel PROS1 c.1113T-->GG frameshift mutation in a family with mixed type I/type III protein S deficiency.

We report a family with type I and type III protein S (PS) deficiency, which showed to be phenotypic variants of the same genetic disease. Direct sequencing analysis of the PROS1 gene was performed to establish the genotype. The ratio of protein C antigen and total PS antigen levels (protein C/S ratio) was used to classify subjects at risk of venous thromboembolism. All PS deficient subjects had increased protein C/S ratios as well as a novel PROS1 c.1113T-->GG frameshift mutation.

Female↗

A frameshift mutation leading to type 1 antithrombin deficiency and thrombosis.

Type 1 antithrombin III (ATIII) deficiency, which is the commonest form of inherited ATIII defect, is characterized by a quantitative reduction in both immunologically and functionally detectable protein. This condition is associated with a high incidence of thromboembolic disorder. Previous investigations have shown that the ATIII genes in the majority of cases are grossly intact, but the precise underlying molecular defects remain unknown. We have investigated the molecular basis of a type 1 ATIII deficiency in an Italian kindred by enzymatic amplification of the ATIII gene sequences in affected family members and direct sequencing of the amplified genomic DNA. A novel mutation, the deletion of a single T in the second position of codon 119, was identified in each of the affected individuals. The resulting frameshift leads to a premature termination in codon 126, effectively resulting in a null allele.

Adult↗

Two frameshift mutations in the cystic fibrosis gene.

Cystic fibrosis (CF) is a recessive disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene. We have identified in exon 7 two frameshift mutations, one caused by a two-nucleotide insertion and the other caused by a one-nucleotide deletion; these mutations--CF1154insTC and CF1213delT, respectively, are predicted to shift the reading frame of the protein and to introduce UAA(ochre) termination codons at residues 369 and 368.

Adolescent↗

An insertional frameshift mutation of the beta-spectrin gene associated with elliptocytosis in spectrin nice (beta 220/216).

Spectrin Nice (beta 220/216) is a spectrin variant associated with a shortened beta chain found in a patient with elliptocytosis. The shortened beta chain (beta' chain) appeared as an additional band of approximately 216 Kd on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and was defective in its ability to be phosphorylated. There were increased amounts of spectrin dimers in crude spectrin extracts from the propositus and the association constant of spectrin dimer self-association was decreased. There was an associated increase of the alpha I 74-Kd fragment from the alpha chain after partial trypic digestion of spectrin. To identify the underlying molecular defect, we analyzed cDNA for beta spectrin obtained by polymerase chain reaction amplification of reverse-transcribed reticulocyte messenger RNA from peripheral blood of the propositus. DNA sequencing of individual as well as pooled subclones showed that two extra bases (GA) are inserted in codon no. 2046 in one allele of the beta-spectrin gene. The insertion results in a frameshift mutation and generates an aberrant C-terminus truncated by about 4 Kd, consistent with the estimated size of the beta' chain observed. By allele-specific oligonucleotide hybridization, the insertion was shown to be present in the propositus and absent in his parents, confirming a previous proposal that it is a de novo mutation. The determination of the location of the mutation in spectrin Nice points to specific regions of the beta-spectrin chain where phosphorylation may occur. A model is proposed to describe the interaction between the alpha- and beta-spectrin chains and to explain the effects of the mutation found in spectrin Nice on the trypsin digestion pattern of its associated alpha chain.

Adolescent↗

First frameshift mutation in the active protein S gene associated with a quantitative hereditary deficiency.

The authors used a strategy combining the amplification-refractory mutations system (ARMS) and denaturing gradient gel electrophoresis (DGGE) to screen the active protein S (PS) gene in a family with PS deficiency, and found a frameshift mutation in exon V. The protein, if expressed, would have an aberrant amino acid sequence from positions 82 to 90 and a premature stop codon in position 91. The mutation co-segregated with the deficient phenotype and was not found in 120 normal chromosomes. It is proposed that the deletion of a T in the codon corresponding to Pro 82 described here is responsible for the deficient phenotype.

Adult↗

Exon skipping and translation in patients with frameshift deletions in the dystrophin gene.

Although many Duchenne muscular dystrophy patients have a deletion in the dystrophin gene which disrupts the translational reading frame, they express dystrophin in a small proportion of skeletal muscle fibers ("revertant fibers"). Antibody studies have shown, indirectly, that dystrophin synthesis in revertant fibers is facilitated by a frame-restoring mechanism; in the present study, the feasibility of mRNA splicing was investigated. Dystrophin transcripts were analyzed in skeletal muscle from individuals possessing revertant fibers and a frameshift deletion in the dystrophin gene. In each case a minor in-frame transcript was detected, in which exons adjacent to those deleted from the genome had been skipped. There appeared to be some correlation between the levels of in-frame transcripts and the predicted translation products. Low levels of alternatively spliced transcripts were also present in normal muscle. The results provide further evidence of exon skipping in the dystrophin gene and indicate that this may be involved in the synthesis of dystrophin by revertant fibers.

Base Sequence↗

[Effect of structural features of nitro-derivatives of fluorenone and biphenyl on frameshift mutagenesis in tester strains of Salmonella typhimurium].

Comparative mutagenic activity of 7 derivatives of biphenyl and fluorenone, 4,4'-dinitrobiphenyl-2,2'-dicarboxylic acid; 4,4',6,6'-tetranitrobiphenyl-2,2'-dicarboxylamide; 2-nitrofluorenone-5-carboxylic acid; 2,7-dinitrofluorenone-5-carboxylic acid; 2,7-dinitrofluorenone-5-carboxylamide; 2-nitrofluorenone-5,7-dicarboxylic acid; 2,4-dinitrofluorenone-5,7-dicarboxylic acid was studied. The highest activity was demonstrated for 2,7-DNF-5-KA and 2,7-DNF-5,7-DK which induced frameshift mutations in the tester strains Salmonella typhimurium TA1537, TA97, TA1538, TA98. High mutagenicity of these compounds is correlated with the position of nitro-groups and the effects of carboxylic and carboxyamide groups.

Amides↗