Identification of Novel High-Frequency DNA Methylation Changes in Breast Cancer

Recent data have revealed that epigenetic alterations, including DNA methylation and chromatin structure changes, are among the earliest molecular abnormalities to occur during tumorigenesis. The inherent thermodynamic stability of cytosine methylation and the apparent high specificity of the alterations for disease may accelerate the development of powerful molecular diagnostics for cancer. We report a genome-wide analysis of DNA methylation alterations in breast cancer. The approach efficiently identified a large collection of novel differentially DNA methylated loci (∼200), a subset of which was independently validated across a panel of over 230 clinical samples. The differential cytosine methylation events were independent of patient age, tumor stage, estrogen receptor status or family history of breast cancer. The power of the global approach for discovery is underscored by the identification of a single differentially methylated locus, associated with the GHSR gene, capable of distinguishing infiltrating ductal breast carcinoma from normal and benign breast tissues with a sensitivity and specificity of 90% and 96%, respectively. Notably, the frequency of these molecular abnormalities in breast tumors substantially exceeds the frequency of any other single genetic or epigenetic change reported to date. The discovery of over 50 novel DNA methylation-based biomarkers of breast cancer may provide new routes for development of DNA methylation-based diagnostics and prognostics, as well as reveal epigenetically regulated mechanism involved in breast tumorigenesis

Measuring Cytosine Methylation within Epigenetically Mosaic Ramets of Elaeis Guineensis for Mantling Risk Prediction

DNA methylation and histone modifications allow for distinct cell identities to emerge from the same set of genomic instructions within multicellular organisms. Though the basis of epigenetic regulation is similar for all eukaryotes, the multiple contexts in which cytosine methylation occur in plants adds to the complexity. Maintaining proper epigenetic marks is vital to appropriate plant development and survival, and crop propagation methods can disrupt these marks, leading to phenotypic alterations. A better understanding of the effects of epigenetic changes may continue to allow for further improvement, while avoiding undesirable effects, in agriculturally important species, such as oil palm.Though it is the most consumed vegetable oil and utilizes land resources the most efficiently of all major vegetable oils, oil palm has substantial environmental and socioeconomic impacts. While breeding programs have increased oil yields, further improvements backed by better understanding the genome and epigenome can be made. Micropropagation of elite palms intended to further this goal have introduced a major negative somaclonal variant, mantling, which dramatically reduces oil yields in affected ramets. The cause of mantling was determined to be caused by disturbed cytosine methylation within Karma, a LINE retrotransposon, located within an intron of the MADS-box gene, EgDEF1. Hypomethylation induces an altered form of this transcription factor, leading to aberrant flower and fruit formation. This study investigated the Karma DMR to determine if measurements of cytosine methylation within leaf samples can accurately predict risk of mantling. The assay designed to measure cytosine methylation within the DMR can identify risk of mantling with 90% sensitivity 84% specificity. This research also gave insight into the mechanics of cytosine methylation reversion and the resulting epigenetic mosaicism in oil palm ramets.</p

Massively parallel bisulphite pyrosequencing reveals the molecular complexity of breast cancer-associated cytosine-methylation patterns obtained from tissue and serum DNA

Cytosine-methylation changes are stable and thought to be among the earliest events in tumorigenesis. Theoretically, DNA carrying tumor-specifying methylation patterns escape the tumors and may be found circulating in the sera from cancer patients, thus providing the basis for development of noninvasive clinical tests for early cancer detection. Indeed, using methylation-specific PCR-based techniques, several groups reported the detection of tumor-associated methylated DNA in the sera from cancer patients with varying clinical success. However, by design, such analytical approaches allow assessment of the presence of molecules with only one methylation pattern, leaving the bigger picture unexplored. The limited knowledge about circulating DNA methylation patterns hinders the efficient development of clinical methylation tests and testing platforms. Here, we report the results of a comprehensive methylation pattern analysis from breast cancer clinical tissues and sera obtained using massively parallel bisulphite pyrosequencing. The four loci studied were recently discovered by our group, and demonstrated to be powerful epigenetic biomarkers of breast cancer. The detailed analysis of more than 700,000 DNA fragments derived from more than 50 individuals (cancer and cancer-free) revealed an unappreciated complexity of genomic cytosine-methylation patterns in both tissue derived and circulating DNAs. Both tumor and cancer-free tissues (as well as sera) contained molecules with nearly every conceivable cytosine-methylation pattern at each locus. Tumor samples displayed more variation in methylation level than normal samples. Importantly, by establishing the methylation landscape within circulating DNA, this study has better defined the development challenges facing DNA methylation-based cancer-detection tests

Identification of novel high-frequency DNA methylation changes in breast cancer.

Recent data have revealed that epigenetic alterations, including DNA methylation and chromatin structure changes, are among the earliest molecular abnormalities to occur during tumorigenesis. The inherent thermodynamic stability of cytosine methylation and the apparent high specificity of the alterations for disease may accelerate the development of powerful molecular diagnostics for cancer. We report a genome-wide analysis of DNA methylation alterations in breast cancer. The approach efficiently identified a large collection of novel differentially DNA methylated loci (approximately 200), a subset of which was independently validated across a panel of over 230 clinical samples. The differential cytosine methylation events were independent of patient age, tumor stage, estrogen receptor status or family history of breast cancer. The power of the global approach for discovery is underscored by the identification of a single differentially methylated locus, associated with the GHSR gene, capable of distinguishing infiltrating ductal breast carcinoma from normal and benign breast tissues with a sensitivity and specificity of 90% and 96%, respectively. Notably, the frequency of these molecular abnormalities in breast tumors substantially exceeds the frequency of any other single genetic or epigenetic change reported to date. The discovery of over 50 novel DNA methylation-based biomarkers of breast cancer may provide new routes for development of DNA methylation-based diagnostics and prognostics, as well as reveal epigenetically regulated mechanism involved in breast tumorigenesis

Oil palm genome sequence reveals divergence of interfertile species in Old and New worlds

Oil palm is the most productive oil-bearing crop. Although it is planted on only 5% of the total world vegetable oil acreage, palm oil accounts for 33% of vegetable oil and 45% of edible oil worldwide, but increased cultivation competes with dwindling rainforest reserves. We report the 1.8-gigabase (Gb) genome sequence of the African oil palm Elaeis guineensis, the predominant source of worldwide oil production. A total of 1.535 Gb of assembled sequence and transcriptome data from 30 tissue types were used to predict at least 34,802 genes, including oil biosynthesis genes and homologues of WRINKLED1 (WRI1), and other transcriptional regulators, which are highly expressed in the kernel. We also report the draft sequence of the South American oil palm Elaeis oleifera, which has the same number of chromosomes (2n = 32) and produces fertile interspecific hybrids with E. guineensis but seems to have diverged in the New World. Segmental duplications of chromosome arms define the palaeotetraploid origin of palm trees. The oil palm sequence enables the discovery of genes for important traits as well as somaclonal epigenetic alterations that restrict the use of clones in commercial plantings, and should therefore help to achieve sustainability for biofuels and edible oils, reducing the rainforest footprint of this tropical plantation crop

The oil palm SHELL gene controls oil yield and encodes a homologue of SEEDSTICK

A key event in the domestication and breeding of the oil palm Elaeis guineensis was loss of the thick coconut-like shell surrounding the kernel. Modern E. guineensis has three fruit forms, dura (thick-shelled), pisifera (shell-less) and tenera (thin-shelled), a hybrid between dura and pisifera. The pisifera palm is usually female-sterile. The tenera palm yields far more oil than dura, and is the basis for commercial palm oil production in all of southeast Asia. Here we describe the mapping and identification of the SHELL gene responsible for the different fruit forms. Using homozygosity mapping by sequencing, we found two independent mutations in the DNA-binding domain of a homologue of the MADS-box gene SEEDSTICK (STK, also known as AGAMOUS-LIKE 11), which controls ovule identity and seed development in Arabidopsis. The SHELL gene is responsible for the tenera phenotype in both cultivated and wild palms from sub-Saharan Africa, and our findings provide a genetic explanation for the single gene hybrid vigour (or heterosis) attributed to SHELL, via heterodimerization. This gene mutation explains the single most important economic trait in oil palm, and has implications for the competing interests of global edible oil production, biofuels and rainforest conservation. © 2013 Macmillan Publishers Limited. All rights reserved

Loss of Karma transposon methylation underlies the mantled somaclonal variant of oil palm

Somaclonal variation arises in plants and animals when differentiated somatic cells are induced into a pluripotent state, but the resulting clones differ from each other and from their parents. In agriculture, somaclonal variation has hindered the micropropagation of elite hybrids and genetically modified crops, but the mechanism responsible remains unknown. The oil palm fruit 'mantled' abnormality is a somaclonal variant arising from tissue culture that drastically reduces yield, and has largely halted efforts to clone elite hybrids for oil production. Widely regarded as an epigenetic phenomenon, 'mantling' has defied explanation, but here we identify the MANTLED locus using epigenome-wide association studies of the African oil palm Elaeis guineensis. DNA hypomethylation of a LINE retrotransposon related to rice Karma, in the intron of the homeotic gene DEFICIENS, is common to all mantled clones and is associated with alternative splicing and premature termination. Dense methylation near the Karma splice site (termed the Good Karma epiallele) predicts normal fruit set, whereas hypomethylation (the Bad Karma epiallele) predicts homeotic transformation, parthenocarpy and marked loss of yield. Loss of Karma methylation and of small RNA in tissue culture contributes to the origin of mantled, while restoration in spontaneous revertants accounts for non-Mendelian inheritance. The ability to predict and cull mantling at the plantlet stage will facilitate the introduction of higher performing clones and optimize environmentally sensitive land resources