The Relationship Between DNA Methylation in Key Region and the Differential Expressions of Genes in Human Breast Tumor Tissue
DNA AND CELL BIOLOGY
Authors: Jin, Wen; Li, Qian-Zhong; Zuo, Yong-Chun; Cao, Yan-Ni; Zhang, Lu-Qiang; Hou, Rui; Su, Wen-Xia
Abstract
Breast cancer has a high mortality rate for females. Aberrant DNA methylation plays a crucial role in the occurrence and progression of breast carcinoma. By comparing DNA methylation differences between tumor breast tissue and normal breast tissue, we calculate and analyze the distributions of the hyper- and hypomethylation sites in different function regions. Results indicate that enhancer regions are often hypomethylated in breast cancer. CpG islands (CGIs) are mainly hypermethylated, while the flanking CGI (shores and shelves) is more easily hypomethylated. The hypomethylation in gene body region is related to the upregulation of gene expression, and the hypomethylation of enhancer regions is closely associated with gene expression upregulation in breast cancer. Some key hypomethylation sites in enhancer regions and key hypermethylation sites in CGIs for regulating key genes are, respectively, found, such as oncogenes ESR1 and ERBB2 and tumor suppressor genes FBLN2, CEBPA, and FAT4. This suggests that the recognizing methylation status of these genes will be useful for the diagnosis of breast cancer.
Identification of a Novel Candidate Gene for Serrated Polyposis Syndrome Germline Predisposition by Performing Linkage Analysis Combined With Whole-Exome Sequencing
CLINICAL AND TRANSLATIONAL GASTROENTEROLOGY
Authors: Toma, Claudio; Diaz-Gay, Marcos; Soares de Lima, Yasmin; Arnau-Collell, Coral; Franch-Exposito, Sebastia; Munoz, Jenifer; Overs, Bronwyn; Bonjoch, Laia; Carballal, Sabela; Ocana, Teresa; Cuatrecasas, Miriam; Diaz de Bustamante, Aranzazu; Castells, Antoni; Bujanda, Luis; Cubiella, Joaquin; Balaguer, Francesc; Rodriguez-Alcalde, Daniel; Fullerton, Janice M.; Castellvi-Bel, Sergi
Abstract
OBJECTIVES: Serrated polyposis syndrome (SPS) is a complex disorder with a high risk of colorectal cancer for which the germline factors remain largely unknown. Here, we combined whole-exome sequencing (WES) and linkage studies in families with multiple members affected by SPS to identify candidate genes harboring rare variants with higher penetrance effects. METHODS: Thirty-nine affected subjects from 16 extended SPS families underwent WES. Genome-wide linkage analysis was performed under linear and exponential models. The contribution of rare coding variants selected to be highly pathogenic was assessed using the gene-based segregation test. RESULTS: significant linkage peak was identified on chromosome 3p25.2-p22.3 (maxSNP = rs2293787; LODlinear = 2.311, LODexp = 2.11), which logarithm of the odds (LOD) score increased after fine mapping for the same marker (maxSNP = rs2293787; LODlinear = 2.4, LODexp = 2.25). This linkage signal was replicated in 10 independent sets of random markers from this locus. To assess the contribution of rare variants predicted to be pathogenic, we performed a family-based segregation test with 11 rare variants predicted to be deleterious from 10 genes under the linkage intervals. This analysis showed significant segregation of rare variants with SPS in CAPT7, TMEM43, NGLY1, and FBLN2 genes (weighted Pvalue > 0.007). DISCUSSION: Protein network analysis suggested FBLN2 as the most plausible candidate genes for germline SPS predisposition. Etiologic rare variants implicated in disease predisposition may be identified by combining traditional linkage with WES data. This powerful approach was effective for the identification of a new candidate gene for hereditary SPS.