The DNA hypomethylation that occurs when embryonic stem cells (ESCs) are directed to the ground state of naive pluripotency by culturing in two small molecule inhibitors (2i) results in ...redistribution of polycomb (H3K27me3) away from its target loci. Here, we demonstrate that 3D genome organization is also altered in 2i, with chromatin decompaction at polycomb target loci and a loss of long-range polycomb interactions. By preventing DNA hypomethylation during the transition to the ground state, we are able to restore to ESC in 2i the H3K27me3 distribution, as well as polycomb-mediated 3D genome organization that is characteristic of primed ESCs grown in serum. However, these cells retain the functional characteristics of 2i ground-state ESCs. Our findings demonstrate the central role of DNA methylation in shaping major aspects of 3D genome organization but caution against assuming causal roles for the epigenome and 3D genome in gene regulation and function in ESCs.
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•The altered 3D genome of 2i ESCs is due to polycomb re-distribution•Stopping DNA hypomethylation and genome re-organization does not affect 2i cell state•Hypomethylated mouse blastocysts have a similar 3D chromatin organization to 2i ESCs
McLaughlin et al. demonstrate that the global DNA methylation state directs the PRC-dependent 3D organization of mouse ESCs and probably early blastocysts. Their findings highlight a central role for DNA methylation and its influence on polycomb, in shaping major aspects of 3D genome organization in stem cells.
Epigenetic silencing is the reversible inactivation of a gene transcription which occurs as a result of changes in the structure of the chromatin that can be successfully inherited from parent to ...daughter cells. It involves non-genetic mutations within the genome, as well as post-transcriptional and post-translational mechanisms. Existence of these mechanisms at various levels warrants their role in development and disease and thus it is crucial to study different factors and mechanisms of silencing. The aim of our study was to establish a method for rapid screening for the loss of epigenetic silencing in mammalian cells, to identify factor(s) involved in epigenetic silencing, and to get insights into their mechanism of action. For this purpose, we used RNAi screening approach using shRNAs that targeted our genes of interest. We employed a modified mouse cell line which contained a GFP transgene under the control of CMV promoter which has been silenced by epigenetic modifications. Our screening identified several proteins as epigenetic silencing regulators including Kat5/Tip60, an acetyltransferase of MYST family of proteins. To characterize its function, we performed preliminary experiments using microscopy and Western blot analysis of histone marks. We observed changes in H4 acetylation levels in Kat5/Tip60 knockdown cells. Our study thus serves as a pilot for a genome-wide silencing screening using mammalian cells, and provides preliminary results suggesting that Kat5 can be considered as a silencing factor, which, we propose, could function by maintaining H4 acetylation patterns.
The Journal of Child and Family Studies states that there have been more mass shootings within the last 18 years than in the entire 20th century combined, with 77% carried out by adolescents. This ...case study aims to evaluate the clinical presentation of post-traumatic stress disorder (PTSD) in an adolescent by highlighting the clinical course of a school shooting survivor. Here, we present the case of a 15-year-old female who presented to the emergency department (ED) of the University Hospital Medical Center (UHMC) under the Baker Act by the police for self-injury and self-harm. She had been admitted three times to the psychiatric hospital, all following the trauma of surviving the shooting. She met the criteria for PTSD and was triggered by graphics in the news outlets and social media. As clinicians working with PTSD adolescents, we must be cognizant of these factors as we think about prognosis and create a comprehensive treatment plan. This case study brings to our attention how complex and multifaceted PTSD patients can be in this day and age where social media, news outlets, and television are so pervasive. Three clinical pearls to take home from this patient encounter are: understanding the importance of news and media in modern-day PTSD diagnosis, how certain avoidance behaviors can delay remission, and how uncontrolled re-exposure can lead to poorer outcomes in children and adolescents specifically. It is no longer a rare occurrence to have a patient who has survived a mass school shooting. As a result of this unfortunate reality, clinicians need to be able to recognize and treat symptoms of PTSD in adolescent patients. We must be equipped to expect the interplay of modern triggers such as social media and news media and how it may affect adolescent patients.
In a shift that may cause Spanish speakers some cognitive dissonance, 415-unit chain El Pollo Loco, which means "the crazy chicken," will announce that it will start serving beef. The chain will ...begin adding grilled steak tacos, steak quesadillas and steak over rice to menus on Saturday. The move comes as the chain has been struggling to sell take-out family dinners of multiple chicken parts and sides, which make up about half of its sales, in markets with high unemployment.
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