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DNA methylation (5mC) is a promising biomarker for detecting circulating tumor DNA (ctDNA), providing information on a cell9s genomic regulation, developmental lineage, and molecular age. Sequencing assays for detecting ctDNA methylation involve pre-processing steps such as immunoprecipitation, enzymatic treatment, or the most common method, sodium bisulfite treatment. These steps add complexity and time that pose a challenge for clinical labs, and bisulfite treatment in particular degrades input DNA and can result in loss of informative ctDNA fragmentation patterns. In this feasibility study, we demonstrate that whole genome sequencing of circulating cell-free DNA using conventional Oxford Nanopore Technologies (ONT) sequencing can accurately detect cell-of-origin and cancer-specific 5mC changes while preserving important fragmentomic information. The simplicity of this approach makes it attractive as a liquid biopsy assay for cancer as well as non-cancer applications in emergency medicine.

e15014 Background: Nucleosomes are the repeating unit of chromatin that contain important signals for proper genomic function and transcriptional activity. Upon cell death, chromatin is fragmented, and nucleosomes are released into circulation and thus, detectable in liquid biopsy. Cell death naturally occurs over time and increases in a variety of diseases resulting in elevated levels of circulating nucleosomes and the genetic and epigenetic signatures they carry. These signatures contain important information about the cells from which they were derived, as well as the reason for them being in circulation. Methods: We measured circulating nucleosome levels, using Volition’s Nu.Q H3.1 sandwich ELISA across a healthy cohort spanning 40-85 years of age as well as patients whom had been diagnosed with Non-Hodgkin's Lymphoma (NHL), some of which were untreated and others that had undergone treatment. Additionally, to demonstrate that the correlation between nucleosome (Nu.Q) levels and copy number alterations is specific to cancer, we assessed the genomic integrity of an NHL sample with a Nu.Q level of 744 ng/ml and a sepsis sample with Nu.Q level of 3,281 ng/ml using low coverage Oxford Nanopore whole genome sequencing to identify genomic amplifications and deletions. We further used cell type specific methylation patterns to identify the cell of origin of cfDNA in each sample. Results: Importantly, we found no significant correlation between nucleosome level and age in our healthy cohort (R2= 0.0004; 40-49: N = 10, mean = 39 ng/ml; 50-59: N = 10, mean = 18 ng/ml; 60-69: N = 10, mean = 35 ng/ml; 70-79: N = 15, mean = 34 ng/ml; 80-85: N = 5, mean = 32 ng/ml). We did however find elevated nucleosome levels in untreated NHL patients (N = 4, mean 646 ng/ml) and that nucleosome levels in NHL patients that had undergone treatment were reduced (N = 29, mean = 180 ng/ml). Using copy number changes, we found that the fraction of cfDNA estimated to be derived from the tumor in the NHL sample was 54% and were able to detect amplifications in chromosomes 10, 11 and 18 and deletions in chromosomes 1, 8, 17, 18 and 23, whereas we found no copy number alterations present in the cfDNA sample derived from a sepsis patient and a tumor fraction of 0. Furthermore, using cell type specific methylation patterns to deconvolute the data we found that a large fraction of the cfDNA in the NHL sample was derived from B-cells consistent with the NHL sample being of B-cell origin whereas we determined that the cell of origin of the cfDNA in the sepsis sample was Neutrophils. Conclusions: This data shows that nucleosome levels, as measured by Nu.Q, can be used in conjunction with shallow sequencing and DNA methylation profiles to define tumor fraction and cell of origin in liquid biopsy.

Fragile X syndrome is the most frequent cause of inherited intellectual disability. The primary molecular defect in this disease is the expansion of a CGG repeat in the 5' region of the fragile X mental retardation1 (FMR1) gene, leading to de novo methylation of the promoter and inactivation of this otherwise normal gene, but little is known about how these epigenetic changes occur during development. In order to gain insight into the nature of this process, we have used cell fusion technology to recapitulate the events that occur during early embryogenesis. These experiments suggest that the naturally occurring Fragile XFMR1 5' region undergoes inactivation post implantation in a Dicer/Ago-dependent targeted process which involves local SUV39H-mediated tri-methylation of histone H3K9. It thus appears that Fragile X syndrome may come about through inadvertent siRNA-mediated heterochromatinization.

Summary We show here that singular loss of the Bright/Arid3A transcription factor leads to reprograming of mouse embryonic fibroblasts (MEFs) and enhancement of standard four-factor (4F) reprogramming. Bright-deficient MEFs bypass senescence and, under standard embryonic stem cell (ESC) culture conditions, spontaneously form clones that in vitro express pluripotency markers, differentiate to all germ lineages, and in vivo form teratomas and chimeric mice. We demonstrate that BRIGHT binds directly to the promoter/enhancer regions of Oct4, Sox2, and Nanog to contribute to their repression in both MEFs and ESCs. Thus, elimination of the BRIGHT barrier may provide an approach for somatic cell reprogramming., Highlights • Loss of Bright can alone reprogram or enhance conventional four-factor reprogramming • Bright directly represses Oct4, Sox2, and Nanog • Bright may function in somatic and embryonic stem cells to enforce differentiation, Popowski et al. show that loss of the transcription factor Bright/Arid3A induces reprogramming in mouse embryonic fibroblasts (MEFs) and enhancement of standard four-factor reprograming. Bright-deficient reprogrammed cells express all pluripotency markers and are capable of forming teratomas and chimeric mice. Bright binds directly to the promoter/enhancer regions of Oct4, Sox2, and Nanog and contributes to their repression in both MEFs and embryonic stem cells.

Significance Even though DNA methylation is known to be correlated with gene repression, it has never been demonstrated that this modification must indeed be removed from a gene in order for it to become activated during cell differentiation in vivo. In this paper, we inactivated the enzymes responsible for the demethylation reaction in the B-cell lineage and in this manner have shown that this epigenetic mark plays a critical role in development, independently of the many specific transcription factors that direct the selection of genes involved in cell differentiation. Our study is the first to our knowledge to causally connect all of the molecular components necessary to prove the link between the Tet enzymes, CpG demethylation, expression, and phenotype.

Sexual dimorphisms are typically attributed to the hormonal differences arising once sex differentiation has occurred. However, in some sexually dimorphic diseases that differ in frequency but not severity, the differences cannot be logically connected to the sex hormones. Therefore, we asked whether any aspect of sexual dimorphism could be attributed to chromosomal rather than hormonal differences. Cells taken from mice at d 10.5 postconception (PC) before sexual differentiation, at d 17.5 PC after the first embryonic assertion of sexual hormones, and at postnatal day 17 (puberty) were cultured and exposed to 400 μM ethanol or 20 μM camptothecin or to infection with influenza A virus (multiplicity of infection of 5). The results showed that untreated male and female cells of the same age grew at similar rates and manifested similar morphology. However, they responded differently to the applied stressors, even before the production of fetal sex hormones. Furthermore, microarray and qPCR analyses of the whole 10.5 PC embryos also revealed differences in gene expression between male and female tissues. Likewise, the exposure of cells isolated from fetuses and adolescent mice to the stressors and/or sex hormones yielded expression patterns that reflected chromosomal sex, with ethanol feminizing male cells and masculinizing female cells. We conclude that cells differ innately according to sex irrespective of their history of exposure to sex hormones. These differences may have consequences in the course of sexually dimorphic diseases and their therapy.—Penaloza, C., Estevez, B., Orlanski, S., Sikorska, M., Walker, R., Smith, C., Smith, B., Lockshin R. A., Zakeri, Z. Sex of the cell dictates its response: differential gene expression and sensitivity to cell death inducing stress in male and female cells.

During embryogenesis there is an exquisite orchestration of cellular division, movement, differentiation, and death. Cell death is one of the most important aspects of organization of the developing embryo, as alteration in timing, level, or pattern of cell death can lead to developmental anomalies. Cell death shapes the embryo and defines the eventual functions of the organs. Cells die using different paths; understanding which path a dying cell takes helps us define the signals that regulate the fate of the cell. Our understanding of cell death in development stems from a number of observations indicating genetic regulation of the death process. With today's increased knowledge of the pathways of cell death and the identification of the genes whose products regulate the pathways we know that, although elimination of some of these gene products has no developmental phenotype, alteration of several others has profound effects. In this review we discuss the types and distributions of cell death seen in developing mammalian embryos as well as the gene products that may regulate the process.