Project description:Analysis of the transcriptome of Tex19.1-/- mouse embryonic stem cells generated by sequential gene targeting in E14Tg2a (129/Ola) parental embryonic stem cells.
Project description:Background: MORC proteins are involved in epigenetic gene silencing in a wide variety of eukaryotic organisms. Deletion of MORCs result in several developmental abnormalities and their dysregulation has been implicated in developmental disease and multiple cancers. Specifically, mutations of mammalian MORC3 have been associated with immune system defects, Down syndrome and human cancers such as bladder, uterine, stomach, and lung cancers, and diffuse large B cell lymphomas. While previous studies have shown that MORC3 binds to H3K4me3 in vitro and overlaps with H3K4me3 ChIP-seq peaks in mouse embryonic stem cells, the mechanism by which MORC3 regulates gene expression is unknown. Results: In this study, we find that MORC3 functions as an epigenetic silencer of endogenous retroviruses (ERVs) in mouse embryonic stem cells (mESCs). Loss of MORC3 results in upregulation of ERVs, specifically those belonging to the LTR class of retrotransposons. Using ChIP-seq, we measure the genome-wide localization of MORC3 in wild-type cells and find that MORC3 binds to ERVs suggesting its direct role in regulating ERV expression. Previous studies have shown that these ERVs are marked by repressive histone mark H3K9me3 which plays a key role in their silencing. Interestingly, we find that the levels of H3K9me3 do not change substantially upon the loss of MORC3 indicating that MORC3 possibly acts downstream of the TRIM28/SETDB1 complex that deposits H3K9me3 at these loci. Instead, we discover that loss of MORC3 results in increased chromatin accessibility at the ERVs suggesting that MORC3 silences ERVs by compacting DNA in mESCs. Conclusions: Our results reveal MORC3 as a novel regulator of ERV silencing in mouse embryonic stem cells. As early mammalian development is characterized by dynamic changes in ERV expression, the role of MORC3 in silencing ERVs is exciting and could potentially explain the abnormalities observed due to its misregulation during mammalian development.
Project description:Heterochromatin is required to restrict aberrant expression of retrotransposons, but it remains poorly defined due to the underlying repeat-rich sequences. We dissected Suv39h-dependent histone H3 lysine 9 trimethylation (H3K9me3) by genome-wide ChIP-sequencing in mouse embryonic stem cells (ESCs). Refined bioinformatic analyses of repeat subfamilies indicated selective accumulation of Suv39h-dependent H3K9me3 at interspersed repetitive elements that cover ~ 5% of the ESC epigenome. The majority of the ~ 8,150 intact long interspersed nuclear elements (LINEs) and endogenous retroviruses (ERVs), but only a minor fraction of the > 1.8 million degenerate and truncated LINEs/ERVs, are enriched for Suv39h-dependent H3K9me3. Transcriptional repression of these intact LINEs and ERVs is differentially regulated by Suv39h and other chromatin modifiers in ESCs but governed by DNA methylation in committed cells. These data provide a novel function for Suv39h-dependent H3K9me3 chromatin to specifically repress intact retrotransposon elements in the ESC epigenome. ChIP-seq and RNA-seq in mouse ES cells, Neural precursors and MEFs wild type and Suv39h double KO. The input for ES cells is accessioned as GSM1251941. A link to this sample can be found below.
Project description:Heterochromatin is required to restrict aberrant expression of retrotransposons, but it remains poorly defined due to the underlying repeat-rich sequences. We dissected Suv39h-dependent histone H3 lysine 9 trimethylation (H3K9me3) by genome-wide ChIP-sequencing in mouse embryonic stem cells (ESCs). Refined bioinformatic analyses of repeat subfamilies indicated selective accumulation of Suv39h-dependent H3K9me3 at interspersed repetitive elements that cover ~ 5% of the ESC epigenome. The majority of the ~ 8,150 intact long interspersed nuclear elements (LINEs) and endogenous retroviruses (ERVs), but only a minor fraction of the > 1.8 million degenerate and truncated LINEs/ERVs, are enriched for Suv39h-dependent H3K9me3. Transcriptional repression of these intact LINEs and ERVs is differentially regulated by Suv39h and other chromatin modifiers in ESCs but governed by DNA methylation in committed cells. These data provide a novel function for Suv39h-dependent H3K9me3 chromatin to specifically repress intact retrotransposon elements in the ESC epigenome.