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PubMed2001

Familial Mediterranean fever in Lebanon: mutation spectrum, evidence for cases in Maronites, Greek orthodoxes, Greek catholics, Syriacs and Chiites and for an association between amyloidosis and M694V and M694I mutations.

Seventy-nine unrelated Lebanese patients were tested for 15 mutations in the MEFV gene: A761H, A744S, V726A, K695R, M694V, M694I, M694del, M6801 (G --> C), M680I (G --> A) in exon 10, F479L in exon 5, P369S in exon 3, T267I, E167D and E148Q in exon 2, using PCR digestion, ARMS, DGGE and/or sequencing. Mutations were detected in patients belonging to all communities, most interestingly the Maronite, Greek orthodox, Greek catholic, Syriac and Chiite communities. The most frequent mutations are M694V and V726A (27% and 20% of the total alleles respectively). M694I, E148Q and M680I mutations account respectively for 9%, 8% and 5%. Each of the K695R, E167D and F479L mutations was observed once and all the remaining mutations were not encountered. Of the alleles 33% do not carry any of the studied mutations. The mutation spectra, clinical features and severity of the disease differed among the Lebanese communities. The genotype-phenotype analysis showed a significant association (P < 0.001) between amyloidosis and the presence of mutations at codon 694 in exon 10 (both M694V and M694I). None of the patients carrying other mutations developed amyloidosis.

Amyloidosis↗
PubMed1998

Comprehensive mutational analysis of the TSC1 gene: observations on frequency of mutation, associated features, and nonpenetrance.

We performed a comprehensive analysis for mutations in the TSC1 gene using Southern blot analysis, and SSCP and heteroduplex analysis of amplified exons in 13 families with genetic linkage to the TSC1 region, 22 small families without linkage information, and 126 sporadic patients. 17 unique mutations were identified in 21 patients. Mutations were found in 7/13 (54%) TSC1-linked families, 1/22 (5%) small families without linkage, and 13 of 126 (10%) sporadic cases. The mutations were all chain-terminating, with 14 small deletions, 1 small insertion, and 6 nonsense mutations. In families with mutations, all individuals carrying a mutation met formal diagnostic criteria for TSC, apart from a 3-year-old girl who had inherited a deletion mutation, and who had no seizures, normal intelligence, normal abdominal ultrasound, and hypomelanotic macules only on physical exam. We assessed the incidence and severity of mental retardation in the 13 sporadic patients with TSC1 mutations versus the entire sporadic cohort, and found no significant difference. The observations indicate that TSC1 mutations are all inactivating, suggest that TSC1 disease occurs in only 15-20% of the sporadic TSC population, and demonstrate that presymptomatic TSC does occur.

Adolescent↗
PubMed2001

CDKN2A and CDK4 mutation analysis in Italian melanoma-prone families: functional characterization of a novel CDKN2A germ line mutation.

Physical interaction between CDKN2A/p16 and CDK4 proteins regulates the cell cycle progression through the G1 phase and dysfunction of these proteins by gene mutation is implicated in genetic predisposition to melanoma. We analysed 15 Italian melanoma families for germ line mutations in the coding region of the CDKN2A gene and exon 2 of the CDK4 gene. One novel disease-associated mutation (P48T), 3 known pathological mutations (R24P, G101W and N71S) and 2 common polymorphisms (A148T and Nt500 G>C) were identified in the CDKN2A gene. In a family harbouring the R24P mutation, an intronic variant (IVS1, +37 G>C) of uncertain significance was detected in a non-carrier melanoma case. The overall incidence of CDKN2A mutations was 33.3%, but this percentage was higher in families with 3 or more melanoma cases (50%) than in those with only 2 affected relatives (25%). Noteworthy, functional analysis established that the novel mutated protein, while being impaired in cell growth and inhibition assays, retains some in vitro binding to CDK4/6. No variant in the p16-binding region of CDK4 was identified in our families. Our results, obtained in a heterogeneous group of families, support the view that inactivating mutations of CDKN2A contribute to melanoma susceptibility more than activating mutations of CDK4 and that other genetic factors must be responsible for melanoma clustering in a high proportion of families. In addition, they indicate the need for a combination of functional assays to determine the pathogenetic nature of new CDKN2A mutations.

Adult↗
PubMed2004

Occurrence of del(GIB6-D13S1830) mutation in Italian non-syndromic hearing loss patients carrying a single GJB2 mutated allele.

Molecular screening for GJB2 (connexin 26) mutations represents the standard diagnostic approach for the genotype definition of non-syndromic deafness. Nevertheless, a single GJB2 pathogenic mutation is detectable in a relevant number of cases, therefore failing to explain the phenotype. We aimed at assessing the occurrence of the recently described del(GIB6-D13S1830) mutation, occurring in the connexin 30 gene, in a group of Italian hearing-impaired patients carrying a single GJB2 mutated allele. A total of 59 non-syndromic hearing loss (NSHL) patients were screened for GJB2 mutations. Among these, nine NSHL patients were found to be heterozygous for a single GJB2 mutation. These patients, heterozygotes for different GJB2 mutated alleles (35delG, L90P, M34T, V153I), together with 11 additional 35delG/neg cases previously described, were studied for the presence of the del(GIB6-D13S1830) mutation. Two double heterozygotes del(GIB6-D13S1830)/35delG were identified. In both cases the degree of hearing loss was profound. Furthermore, GJB2 molecular screening led to the identification of a novel change (T55G) occurring in compound heterozygosity with the V37I mutation. In conclusion, our data suggest a significant frequency of del(GIB6-D13S1830) mutation in Italian hearing-impaired subjects (10% of unexplained GJB2 heterozygotes) similar to that reported in other European countries.

Connexin 26↗
PubMed2001

Medium-chain acyl-CoA dehydrogenase (MCAD) mutations identified by MS/MS-based prospective screening of newborns differ from those observed in patients with clinical symptoms: identification and characterization of a new, prevalent mutation that results in mild MCAD deficiency.

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most frequently diagnosed mitochondrial beta-oxidation defect, and it is potentially fatal. Eighty percent of patients are homozygous for a common mutation, 985A-->G, and a further 18% have this mutation in only one disease allele. In addition, a large number of rare disease-causing mutations have been identified and characterized. There is no clear genotype-phenotype correlation. High 985A-->G carrier frequencies in populations of European descent and the usual avoidance of recurrent disease episodes by patients diagnosed with MCAD deficiency who comply with a simple dietary treatment suggest that MCAD deficiency is a candidate in prospective screening of newborns. Therefore, several such screening programs employing analysis of acylcarnitines in blood spots by tandem mass spectrometry (MS/MS) are currently used worldwide. No validation of this method by mutation analysis has yet been reported. We investigated for MCAD mutations in newborns from US populations who had been identified by prospective MS/MS-based screening of 930,078 blood spots. An MCAD-deficiency frequency of 1/15,001 was observed. Our mutation analysis shows that the MS/MS-based method is excellent for detection of MCAD deficiency but that the frequency of the 985A-->G mutant allele in newborns with a positive acylcarnitine profile is much lower than that observed in clinically affected patients. Our identification of a new mutation, 199T-->C, which has never been observed in patients with clinically manifested disease but was present in a large proportion of the acylcarnitine-positive samples, may explain this skewed ratio. Overexpression experiments showed that this is a mild folding mutation that exhibits decreased levels of enzyme activity only under stringent conditions. A carrier frequency of 1/500 in the general population makes the 199T-->C mutation one of the three most prevalent mutations in the enzymes of fatty-acid oxidation.

Acyl-CoA Dehydrogenase↗
PubMed1993

The mutational specificity of two Escherichia coli dnaE antimutator alleles as determined from lacI mutation spectra.

In a companion study we have described the isolation of a series of mutants of Escherichia coli that replicate their DNA with increased fidelity. These mutants carry a mutation in the dnaE gene, encoding the alpha (polymerase) subunit of DNA polymerase III holoenzyme, which is responsible for the faithful replication of the bacterial chromosome. The mutants were detected as suppressors of the high mutability of a mutL strain (defective in postreplicative mismatch correction), in which mutations may be considered to arise predominantly from errors of DNA replication. To investigate the specificity of these antimutator effects, we have analyzed spectra of forward mutations in the N-terminal part of the lacI gene (i-d mutations) for two of the mutL dnaE derivatives (dnaE911 and dnaE915), as well as the control mutL strain. DNA sequencing of over 600 mutants revealed that in the mutL background both antimutator alleles reduce specifically transition mutations (A.T-->G.C and G.C-->A.T). However, the two alleles behave differently in this respect. dnaE911 reduces A.T-->G.C more strongly than it does G.C-->A.T, whereas the reverse is true for dnaE915. Second, dnaE911 does not appear to affect either transversion or frameshift mutations, whereas dnaE915 displays a distinct mutator effect for both. This mutator effect of dnaE915 for frameshift mutations was confirmed by the frequency of reversion of the trpE9777 frameshift mutation. The discovery that dnaE antimutator alleles possess distinct specificities supports the notion that DNA polymerases discriminate against errors along multiple pathways and that these pathways can be influenced independently.

Alleles↗
PubMed1995

Positive R plasmid mutator effect on chromosomal mutation to nalidixic acid resistance in nalidixic acid-exposed cultures of Escherichia coli.

Mutation frequencies to nalidixic acid resistance (15 mg/L in nutrient agar) were determined for derivatives of Escherichia coli AB1157 carrying the mutator plasmids R46, R391 or pYD1, or the non-mutator plasmid RP4. Frequencies of mutation remained constant in cultures of AB1157(R46) growing exponentially in drug-free broth, at a level about 12-fold higher than in the strain without plasmid. Mutation frequencies in cultures of strains AB1157(R391) and AB1157(pYD1) were about three times greater than in the control, whereas plasmid RP4 had no effect on spontaneous mutation frequency to nalidixic acid resistance. Exposure of strain AB1157 to 6 mg/L nalidixic acid in nutrient broth killed 80% of cells after 4 h. This enriched the proportion of nalidixic acid-resistant cells present in the surviving cell population giving enhanced "apparent" mutation frequencies. These were further increased by cell division of resistant mutants in the nalidixic acid-containing medium. "Apparent" resistance mutation frequencies in nalidixic acid-exposed cultures of the R46-, R391- or pYD1-carrying derivatives were, at their peak, 447-, 53- and 38-fold higher than in the control, the strain without plasmid, or the RP4-containing strain, respectively. These data illustrate how mutator plasmids like R391 and pYD1, which mediate only small increases in spontaneous mutation, can contribute to the development of clinically-significant levels of quinolone resistance.

Conjugation, Genetic↗
PubMed2002

Ligation of a primer at a mutation: a method to detect low level mutations in DNA.

Detection of low frequency mutations following exposure to mutagens or during the early stages of cancer development is instrumental for risk assessment and molecular diagnosis. We present a sensitive new method to detect trace levels of DNA mutations induced within a large excess of wild-type sequences. The method is based on mutation-induced generation of new restriction enzyme recognition sites. A DNA sequence is amplified from genomic DNA or cDNA using a high fidelity polymerase. The purified PCR product is digested with a restriction enzyme that recognizes the newly generated restriction site, partially dephosphorylated and ligated with an oligonucleotide at the position of the mutation. The ligated oligonucleotide is then utilized in two rounds of PCR to amplify the mutated DNA but not the wild-type allele that contains no restriction site. An A-->T polymorphism in mRNA (tenascin gene, A(2366)-->T, Asn-->Ile) and a G-->A polymorphism in genomic DNA (Ku gene, G(74582)-->A, Val-->Ile), both of which generate a restriction site for the enzyme SAU3A1, demonstrate the application. Eleven patient samples pre-characterized for the G(74582)-->A polymorphism in the repair gene Ku are used to demonstrate the reliability of this approach. This technique quantitatively detects the Ku G-->A polymorphism at a mutant frequency of 1.6x10(-6) relative to the wild-type allele. Mutations in p53 that are frequently induced by mutagens can readily be detected using the present method. As an example, using a second enzyme BbvI, a mutation frequently encountered in human cancers (G(14154)-->A mutation, p53 codon 245, Arg-->Gln) was detected in patient samples. The process does not require radioactivity, utilizes established procedures and overcomes several factors known to produce false positives in RFLP-based assays. The present amplification via primer ligation at the mutation (APRIL-ATM) has potential applications in the detection of mutagen-generated genetic alterations, early detection of tumor marker mutations in bodily discharges and the diagnosis of minimal residual disease.

Adenocarcinoma↗
PubMed1999

Mutation analysis of the BRCA1 and BRCA2 genes in the Belgian patient population and identification of a Belgian founder mutation BRCA1 IVS5 + 3A > G.

Since the identification of the BRCA1 and BRCA2 genes, several hundred different germline mutations in both genes have been reported. Recurrent mutations are rare and mainly due to founder effects. As the mutational spectrum of the BRCA1 and BRCA2 genes in the Belgian patient population is largely unknown, we initiated mutation analysis for the complete coding sequence of both genes in Belgian families with multiple breast and/or ovarian cancer patients and in "sporadic" patients with early onset disease. We completed the analysis in 49 families and in 19 "sporadic" female patients with early onset breast and/or ovarian cancer. In 15 families we identified a mutation (12 mutations in BRCA1 and 3 mutations in BRCA2). In 5 apparently unrelated families the same splice site mutation was identified (BRCA1 IVS5 + 3A > G). Haplotype analysis revealed a common haplotype immediately flanking the mutation in all families suggesting that disease alleles are identical by descent. In none of the 19 sporadic patients was a mutation found.

Adult↗
PubMed2005

BRAF mutation in endometrial carcinoma and hyperplasia: correlation with KRAS and p53 mutations and mismatch repair protein expression.

PURPOSE: Although several gene abnormalities have been reported in endometrial carcinoma, the genetic alterations have not fully been elucidated. Recent studies have revealed frequent activating mutations of the gene for BRAF, an effector of Ras protein in the mitogen-activated protein kinase pathway, in several malignancies. However, the prevalence and significance of BRAF mutations in endometrial carcinoma remain unclear. EXPERIMENTAL DESIGN: We examined BRAF mutations in exons 11 and 15 in 97 cases of endometrial carcinoma (endometrioid type, 78; nonendometrioid type, 19), 9 cases of atypical endometrial hyperplasia, and 20 cases of normal endometrium by direct sequencing. In addition, mutations of KRAS and p53 and the immunohistochemical expression of hMLH1 and hMSH2 were also examined. RESULTS: Of the 97 carcinomas and 9 hyperplasias, 20 (21%) and 1 (11%) had BRAF mutations, most of them at previously unreported sites. Twenty samples of normal endometrium and 21 samples of normal endometrium obtained from sites adjacent to neoplastic lesions had no BRAF mutations. There was no apparent difference in the prevalence of BRAF mutation among stages, histologic subtypes, or grades. Mutations of KRAS and p53 were found in 18 (19%) and 22 (23%) cases, and 65 (67%) and 92 (95%) cases showed positive immunostaining for hMLH1 and hMSH2, respectively. BRAF mutation was more frequently found in hMLH1-negative cases (12 of 32, 41%) than in hMLH1-positive cases (7 of 65, 11%; P = 0.008), suggesting that it is associated with an abnormal mismatch repair function. CONCLUSIONS: These findings suggest that mutations of the BRAF gene are partly involved in the malignant transformation of the endometrium.

Adaptor Proteins, Signal Transducing↗
PubMed2003

X-linked retinitis pigmentosa: RPGR mutations in most families with definite X linkage and clustering of mutations in a short sequence stretch of exon ORF15.

PURPOSE: A comprehensive screening was conducted for RP2 and retinitis pigmentosa GTPase regulator (RPGR) gene mutations including RPGR exon ORF15 in 58 index patients. The frequency of RPGR mutations was assessed in families with definite X-linked recessive disease (xlRP), and a strategy for analyzing the highly repetitive mutational hot spot in exon ORF15 is provided. METHODS: Fifty-eight apparently unrelated index-patients were screened for mutations in all coding exons of the RP2 and the RPGR genes, including splice-sites, by single-strand conformation polymorphism (SSCP) analysis, except for RPGR exon ORF15. A strategy for directly sequencing the large repetitive stretch of exon ORF15 from a 1.6-kb PCR-product was developed. According to pedigree size and evidence for X linkage, families were subdivided into three categories. RESULTS: Screening of 58 xlRP families revealed RP2 mutations in 8% and RPGR mutations in 71% of families with definite X-linked inheritance. Mutations clustered within a approximately 500-bp stretch in exon ORF15. In-frame sequence alterations in exon ORF15 ranged from the deletion of 36 bp to the insertion of 75 bp. CONCLUSIONS: Mutations in the RPGR gene are estimated to cause 15% to 20% of all cases of RP, higher than any other single RP locus. This report provides a detailed strategy to analyze the mutational hot spot in RPGR exon ORF15, which cannot be screened by standard procedures. The discrepancy of the proportion of families linked to the RP3 locus and those having RPGR mutations is resolved in a subset of families with definite X linkage.

Carrier Proteins↗
PubMed2014

Single cell mutational analysis of PIK3CA in circulating tumor cells and metastases in breast cancer reveals heterogeneity, discordance, and mutation persistence in cultured disseminated tumor cells from bone marrow.

BACKGROUND: Therapeutic decisions in cancer are generally guided by molecular biomarkers or, for some newer therapeutics, primary tumor genotype. However, because biomarkers or genotypes may change as new metastases emerge, circulating tumor cells (CTCs) from blood are being investigated for a role in guiding real-time drug selection during disease progression, expecting that CTCs will comprehensively represent the full spectrum of genomic changes in metastases. However, information is limited regarding mutational heterogeneity among CTCs and metastases in breast cancer as discerned by single cell analysis. The presence of disseminated tumor cells (DTCs) in bone marrow also carry prognostic significance in breast cancer, but with variability between CTC and DTC detection. Here we analyze a series of single tumor cells, CTCs, and DTCs for PIK3CA mutations and report CTC and corresponding metastatic genotypes. METHODS: We used the MagSweeper, an immunomagnetic separation device, to capture live single tumor cells from breast cancer patients' primary and metastatic tissues, blood, and bone marrow. Single cells were screened for mutations in exons 9 and 20 of the PIK3CA gene. Captured DTCs grown in cell culture were also sequenced for PIK3CA mutations. RESULTS: Among 242 individual tumor cells isolated from 17 patients and tested for mutations, 48 mutated tumor cells were identified in three patients. Single cell analyses revealed mutational heterogeneity among CTCs and tumor cells in tissues. In a patient followed serially, there was mutational discordance between CTCs, DTCs, and metastases, and among CTCs isolated at different time points. DTCs from this patient propagated in vitro contained a PIK3CA mutation, which was maintained despite morphological changes during 21 days of cell culture. CONCLUSIONS: Single cell analysis of CTCs can demonstrate genotypic heterogeneity, changes over time, and discordance from DTCs and distant metastases. We present a cautionary case showing that CTCs from any single blood draw do not always reflect metastatic genotype, and that CTC and DTC analyses may provide independent clinical information. Isolated DTCs remain viable and can be propagated in culture while maintaining their original mutational status, potentially serving as a future resource for investigating new drug therapies.

Bone Marrow↗
PubMed1997

Three novel mutations and a de novo deletion mutation of the DAX-1 gene in patients with X-linked adrenal hypoplasia congenita.

The DAX-1 [DSS (dosage sensitive sex)-AHC critical region on the X, gene 1] gene is responsible for X-linked adrenal hypoplasia congenita (AHC). However, DAX-1 protein structure-function relationships are not well understood. Identification of missense mutations may help to reveal these relationships. We analyzed the DAX-1 gene from seven patients in six kindreds with X-linked AHC and identified one frameshift mutation, two missense mutations, and three deletion mutations. Case 1 had a 388delAG frameshift mutation, inducing a premature stop codon at position 70. Case 2 had a missense mutation, Lys382Asn, which encodes an asparagine (Asn) for lysine (Lys) at position 382. Sibling cases of 3-1 and 3-2 had a missense mutation of Trp291 Cys, which encodes a substitution of cysteine (Cys) for tryptophan (Try) at position 291. The tryptophan (Trp) at position 291 and lysine (Lys) at position 382 in human DAX-1 protein are highly conserved among other related orphan nuclear receptor superfamily members. Cases 4, 5, and 6 showed deletion mutation. In case 6, a de novo deletion mutation was revealed by both southern hybridization and polymerase chain reaction (PCR) of a GGAA tetranucleotide tandem repeat. These findings suggest that: 1) Trp at position 291 and Lys at position 382, located in the C-terminal presumptive ligand binding domain, are important to the functional role of the DAX-1 protein in adrenal embryogenesis and/or in hypothalamic-pituitary activity; and 2) molecular analysis of the DAX-1 gene may help genetic counseling, even in cases with deletion mutation, because a detection of de novo deletion may exclude another affected or carrier child.

Adrenal Insufficiency↗
PubMed1998

Mutation screening of the BTK gene in 56 families with X-linked agammaglobulinemia (XLA): 47 unique mutations without correlation to clinical course.

OBJECTIVES: To determine the utility of single-stranded conformation polymorphism (SSCP) analysis for mutation screening in the BTK (Bruton's tyrosine kinase) gene, we investigated 56 X-linked agammaglobulinemia (XLA) families. To obtain genotype/ phenotype correlations, predicted protein aberrations were correlated with the clinical course of the disease. PATIENTS: This study included 56 patients with XLA, with or without a positive family history, who were diagnosed on the basis of their clinical features, low peripheral B-cell count, and low immunoglobulin levels. Ten patients with isolated hypogammaglobulinemia and 50 healthy males served as controls. METHODS: SSCP analysis was performed for the entire BTK gene, including the exon-intron boundaries and the promoter region. Structural implications of the missense mutations were investigated by molecular modeling, and the functional consequences of some mutations also were evaluated by in vitro kinase assays and Western blot analysis. RESULTS: We report the largest series of patients with XLA to date. All but 5 of the 56 index patients with XLA screened with SSCP analysis showed BTK gene abnormalities, and in 2 of the 5 SSCP-negative patients, no BTK protein was found by Western blot analysis. There were 51 mutations, including 37 novel ones, distributed across the entire gene. This report contains the first promoter mutation as well as 14 novel missense mutations with the first ones described for the Tec homology domain and the glycine-rich motif in the SH1 domain. Each index patient had a different mutation, except for four mutations, each in two unrelated individuals. This result supports the strong tendency for private mutations in this disease. No mutations were found in the controls. CONCLUSIONS: Our results demonstrate that molecular genetic testing by SSCP analysis provides an accurate tool for the definitive diagnosis of XLA and the discrimination of borderline cases, such as certain hypogammaglobulinemia or common variable immunodeficiency patients with overlapping clinical features. Genotype/ phenotype correlations are not currently possible, making prediction of the clinical course based on molecular genetic data infeasible.

Adolescent↗
PubMed1999

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↗
PubMed1999

Beta-catenin mutations are specific for colorectal carcinomas with microsatellite instability but occur in endometrial carcinomas irrespective of mutator pathway.

Some colorectal tumors with wild-type adenomatous polyposis coli gene have activating mutations in beta-catenin (encoded by CTNNB1) that result in decreased phosphorylation by GSK-3beta and increased signaling through the Tcf/Lef transcription factors. To investigate the relationship between CTNNB1 mutations and underlying pathways of genomic instability, we examined 80 colorectal cancers stratified by the presence or absence of microsatellite instability (MSI). CTNNB1 mutations were identified in 13 (25%) of 53 cancers with high frequency MSI (MSI-H), including 12 point mutations at exon 3 phosphorylation sites (codons 41 and 45) and one deletion of the entire exon 3 degradation box. No CTNNB1 mutations were identified in 27 microsatellite stable or low frequency MSI (MSI-L) colorectal cancers (P < 0.01). In contrast, CTNNB1 mutations were identified in 3 of 9 (33%) MSI-H and 10 of 20 (50%) MSS/MSI-L endometrial carcinomas, suggesting a more generalized involvement in these tumors. Only six (46%) of the endometrial carcinoma CTNNB1 mutations occurred at residues directly phosphorylated by GSK-3beta, and only one of these was at either codon 41 or 45. All point mutations in MSI-H cancers were transitions, whereas 64% of those in MSS/MSI-L cancers were transversions (P < 0.01). The differences in the mutation profiles suggest that there may be molecular fingerprints of CTNNB1 mutations, determined by biological factors related to both tumor type and underlying pathways of genomic instability.

Adenocarcinoma↗
PubMed2000

Analysis of all exons of TSC1 and TSC2 genes for germline mutations in Japanese patients with tuberous sclerosis: report of 10 mutations.

Twenty-seven Japanese patients with the tuberous sclerosis complex (TSC), consisting of 23 sporadic and 4 familial cases, were tested for mutations in the TSC1 and TSC2 genes, using single-strand conformational polymorphism analysis and direct sequencing. Four possible pathogenic mutations were found in the TSC1 gene, including three frame shifts and a nonsense mutation in a familial case. All mutations were expected to result in a truncated hamartin gene product. The TSC2 gene analysis identified six possible pathogenic mutations only in the sporadic cases, including two frame shifts, one in-frame deletion, and three missense mutations. Two of the TSC2 mutations were expected to result in a truncated tuberin gene product. These results of the Japanese TSC patients were compatible with the reports from Europe and the United States, i.e., (1) TSC1 mutations are rarer in sporadic cases than in familial cases, (2) substantial numbers of sporadic cases arise from mutations in the TSC2 gene, and (3) mutations of the TSC1 gene may cause premature truncation of hamartin.

Adolescent↗
PubMed2000

Mutational analysis of 30 Slovenian cystic fibrosis patients compared to known Slovenian and European CF mutation spectra.

More than 800 mutations have been indentified in the CFTR gene. This vast mutation diversity makes the search for molecular defects in cystic fibrosis difficult. Out of 100 Slovenian CF families, we have screened 30, using DGGE and SSCP as mutation detection techniques, while the remaining 70 have been studied previously. Together our and the previous studies have been able to indentify 18 CF mutations which cover 77.6% of the CF alleles in those families. The relative frequency of deltaF508 is 62.7% which is significantly higher than the average reported for the Mediterranean South European region (51.6%). At the same time, significant differences in mutation frequencies were found for the G542X, R1162X, W1282X, N1303K and 3905insT mutations. Several, otherwise rare mutations have been detected, such as: I148T, Q552X, 457TAT-->G, R1006H, 2907delTT, 3667ins4, A559T and G576A. An interesting fact is that A559T was so far found mostly in CF patients of African-American origin. These results imply that a high heterogeneity of CF mutations occurs within the small population of Slovenia, consisting only of 2 million inhabitants. In view of the spectrum and frequencies of detected mutations, Slovenian population expresses characteristics of Mediterranean and central European countries, and at the same time shows also distinctive differences and unique region specific CF mutations (Q685X, D192G, S4X).

Alleles↗