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Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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The MLH1 c.-27C>A and c.85G>T variants are borne on a European ancestral haplotype which underlies an autosomal dominant form of MLH1 epimutation.

ABSTRACT: Lynch syndrome, caused by germline heterozygous mutations of the DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2, or deletions affecting the EPCAM gene upstream of MSH2, is characterized by a predisposition to early-onset colorectal and additional extracolonic cancers. An alternative but rare cause of Lynch syndrome is a constitutional epimutation of MLH1, which is characterized by promoter methylation and transcriptional silencing of a single allele in normal tissues. Worldwide, five families with autosomal dominant transmission of a constitutional MLH1 epimutation linked to an MLH1 haplotype with two single nucleotide variants (c.-27C>A and c.85G>T) have been identified. Array-based genotyping using Affymetrix SNP 6.0 data in four of these families revealed a shared haplotype extending across a ≤2.6 Mb region of chromosome 3p22 encompassing MLH1 and additional flanking genes, indicating common ancestry. Genomic DNA from 5 carriers of the c.-27C>A and c.85G>T variants was hybridized on Affymetrix SNP6.0 array according to manufacturer's procedures

ORGANISM(S): Homo sapiens

SUBMITTER: Ingrid Vogelaar

PROVIDER: E-GEOD-45149 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Dominant MLH1 epimutation linked to 5'UTR variant c.-27C>A

Project description:Constitutional epimutations of tumor suppressor genes manifest as promoter methylation and transcriptional silencing of a single allele in normal somatic tissues, thereby predisposing to cancer. Constitutional MLH1 epimutations occur in individuals with young-onset cancer and demonstrate non-Mendelian inheritance through their reversal in the germline. We report a cancer-affected family showing dominant transmission of soma-wide highly mosaic MLH1 methylation and transcriptional repression linked to a particular genetic haplotype. The epimutation was erased in spermatozoa but reinstated in the somatic cells of the next generation. The affected haplotype harbored two single nucleotide substitutions in tandem: c.-27C>A located near the transcription initiation site and c.85G>T. The c.-27C>A variant significantly reduced transcriptional activity in reporter assays and is the probable cause of this epimutation. Five members of a three-generation Caucasian Lynch syndrome family with an autosomal dominant MLH1 epimutation linked to a single nucleotide variant (c.-27C>A) within the MLH1 5'UTR were examined for copy number variations and retention of heterozygosity on chromosome 3. These five carriers of constitutional MLH1 methylation and the c.-27C>A variant were compared with 300 healthy Caucasian controls from the Wellcome Trust Case Control Consortium using three algorithms (QuantiSNP, PennCNV, COKGEN) to detect any copy number variants. The five family members studied were female (the proband II5, her affected mother I1, and three asymptomatic relatives II2, II4 and III2) are labeled according to the pedigree in Figure 3 of the associated publication (Hitchins et al., Cancer Cell, 2011). The supplementary file 'GSE30348_gw6.lrr_baf.txt' contains log R ratio and B-allele frequency values in a tab-delimited format with one marker per row.

2011-07-01 | E-GEOD-30348 | biostudies-arrayexpress

The MLH1 c.-27C>A and c.85G>T variants are borne on a European ancestral haplotype which underlies an autosomal dominant form of MLH1 epimutation.

Project description:Lynch syndrome, caused by germline heterozygous mutations of the DNA mismatch repair genes MLH1, MSH2, MSH6 and PMS2, or deletions affecting the EPCAM gene upstream of MSH2, is characterized by a predisposition to early-onset colorectal and additional extracolonic cancers. An alternative but rare cause of Lynch syndrome is a constitutional epimutation of MLH1, which is characterized by promoter methylation and transcriptional silencing of a single allele in normal tissues. Worldwide, five families with autosomal dominant transmission of a constitutional MLH1 epimutation linked to an MLH1 haplotype with two single nucleotide variants (c.-27C>A and c.85G>T) have been identified. Array-based genotyping using Affymetrix SNP 6.0 data in four of these families revealed a shared haplotype extending across a ≤2.6 Mb region of chromosome 3p22 encompassing MLH1 and additional flanking genes, indicating common ancestry.

2013-04-01 | GSE45149 | GEO

Dominant MLH1 epimutation linked to 5'UTR variant c.-27C>A

2011-07-01 | GSE30348 | GEO

Primary constitutional MLH1 epimutations: a focal epigenetic event [blood data sets]

Project description:Background: Constitutional MLH1 epimutations are characterized by monoallelic methylation of the MLH1 promoter throughout normal tissues, accompanied by allele-specific silencing. The mechanism underlying primary MLH1 epimutations is currently unknown. The aim of this study was to perform an in-depth characterization of constitutional MLH1 epimutations targeting the aberrantly methylated region around MLH1 and other genomic loci. Methods: Twelve MLH1 epimutation carriers, 61 Lynch syndrome patients and 41 healthy controls, were analyzed by Infinium Human Methylation 450K beadchip, and targeted molecular techniques were used to characterize the MLH1 epimutation in carriers and their inheritance pattern. Results: No nucleotide or structural variants were identified in-cis on the epimutated allele in ten carriers, in which intergenerational methylation erasure was demonstrated in two, suggesting primary type of epimutation. CNVs outside the MLH1 locus were found in two cases. EPM2AIP1-MLH1 CpG island was identified as the sole differentially methylated region in MLH1 epimutation carriers compared to controls. Conclusion: Primary constitutional MLH1 epimutations arise as a focal epigenetic event at the EPM2AIP1-MLH1 CpG island in the absence of cis-acting genetic variants. Further molecular characterization is needed to elucidate the mechanistic basis of MLH1 epimutations and their heritability/reversibility.

2017-11-28 | GSE107351 | GEO

Primary constitutional MLH1 epimutations: a focal epigenetic event [FFPE data sets]

2017-11-28 | GSE107352 | GEO

Highly sensitive MLH1 methylation analysis in blood allows the identification of low-level epigenetic mosaicism

Project description:Constitutional MLH1 epimutations are a rare cause of Lynch syndrome. Low methylation levels (≤10%) have been occasionally described. The aim of this study was the identification of patients with low levels of epigenetic mosaicism in MLH1 gene. Eighteen patients with MLH1 hypermethylated tumors and undetectable methylation in blood as assessed by Methylation-Specific Multiplex Ligation-Dependent Probe Amplification were included (MS-MLPA). Highly sensitive MS-Melting Curve Analysis (MS-MCA) at MLH1 promoter was used to screen for epigenetic mosaicism. Constitutional methylation was confirmed by other methods. Mutational analysis of hereditary cancer genes including MLH1 was performed. MS-MCA analysis identified one case (5.6%) with low levels of methylation (1-2%) in blood DNA. The patient had developed 3 gastrointestinal tumors at ages 22, 24 and 25, sharing MLH1 promoter hypermethylation and loss of heterozygosity associated with c.655A allele. The presence of low MLH1 methylation levels was confirmed by clonal bisulfite sequencing, evidencing the association with c.-93G allele (in phase with c.655G). The extension of the hypermethylated region overlaps with the reported in constitutional MLH1 epimutation carriers. No rare germline variants were identified. The use of highly sensitive techniques such as MS-MCA has demonstrated to be useful for the detection of low MLH1 methylation levels in blood.

2019-05-22 | GSE131541 | GEO

Identification of candidate predisposing copy number variants in familial and early-onset colorectal cancer patients

Project description:In the majority of colorectal cancers (CRC) under clinical suspicion for a hereditary cause, the disease-causing genetic factors are still to be discovered. In order to identify such genetic factors we stringently selected a discovery cohort of 41 CRC index patients with microsatellite-stable tumors. All patients were below 40 years of age at diagnosis and/or exhibited an overt family history. We employed genome-wide copy number profiling using high-resolution SNP-based array CGH on germline DNA, which resulted in the identification of novel copy number variants (CNVs) in 6 patients (15%) encompassing, among others, the cadherin gene CDH18, the bone morphogenetic protein antagonist family gene GREM1, and the breakpoint cluster region gene BCR. In addition, two genomic deletions were encountered encompassing two microRNA genes, hsa-mir-491/KIAA1797 and hsa-mir-646/AK309218. None of these CNVs has previously been reported in relation to CRC predisposition in humans, nor were they encountered in large control cohorts (>1,600 unaffected individuals). Since several of these newly identified candidate genes may be functionally linked to CRC development, our results illustrate the potential of this approach for the identification of novel candidate genes involved in CRC predisposition. Copy number detection was performed using CNAG2.0 software for 250k SNP arrays and using the Affymetrix Genotyping Console v2.1 software for SNP 6.0 arrays, Reference genomes are included in this data set. Germline genomic DNA from 41 patients with early-onset microsatellite stable colorectal cancer was hybridized on Affymetrix Nsp/6.0 SNP-based arrays according to manufacturer's procedures.

2010-11-01 | E-GEOD-13429 | biostudies-arrayexpress

The reversed evolution from multicellularity to unicellularity during carcinogenesis

Project description:Using xenograft-based experimental evolution, we characterize the full life history from initiation to metastasis of a tumor at the genomic and transcriptomic levels. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cell lines or xenograft tumor samples.

2014-11-27 | E-GEOD-63630 | biostudies-arrayexpress

Homo sapiens

Project description:Dominant MLH1 epimutation linked to 5'UTR variant c.-27C>A

| PRJNA143643 | ENA

Affymetrix SNP array data for mammary tumors that recurred after inactivation of the oncogenic PIK3CA-H1047R

Project description:Gain-of-function mutation of PIK3CA represents one of the most common oncogenic events in human malignancy, making PI3K an attractive target for cancer therapy. Despite the great promise of targeted therapy, drug resistance is likely to develop, causing treatment failure. To elucidate resistance mechanisms to PI3K-targeted therapy, we constructed a mouse model of breast cancer conditionally expressing PIK3CA-H1047R. Surprisingly, the majority of mammary tumors induced by PIK3CA-H1047R expression recurred following PIK3CA-H1047R inactivation. Genomic analyses of recurrent tumors revealed multiple lesions, including spontaneous focal amplification of c-Met or c-Myc. While amplification of c-Met allowed tumor survival dependent on activation of endogenous PI3K, tumors with amplification of c-Myc become independent of the PI3K pathway. Functional analyses further demonstrated that c-Myc contributed to tumors’ independence of oncogene and resistance to PI3K inhibition. Together, our data suggest that MYC elevation in tumors may be a potential mechanism conferring resistance to current PI3K-targeted therapies. Affymetrix SNP array analysis was performed with Mouse Diversity Genotyping Arrays (Affymetrix) on genomic DNA extracted from frozen biopsies of 6 recurrent mouse mammary tumor samples. Copy number analysis was performed for the mouse mammary tumors using genomic DNA from normal mammary tissue as the reference for copy number inference.

2011-08-01 | E-GEOD-27691 | biostudies-arrayexpress

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