Project description:Transposable elements (TEs) are ubiquitous in genomes. Many of these TEs remain active and are an important fraction of the transcriptomes with potential effects on the host genomes. The functional impact of TEs is well known for model organisms, however, in transcriptomes analysis of non-model organisms, this information is ignored due to the difficulty in identifying and quantifying TEs. Here we develop ExplorATE, a pipeline that allows the identification and quantification of active TEs in non-model organisms that can be easily implemented within the R environment. Based on simulated data, we show that our pipeline accurately identifies and quantifies TEs, over-performing the commonly used tools in model organisms. We show the implementation of ExplorATE using real data for RNA-seq samples from different tissues (liver, ovary, and brain) of Liolaemus parthenos, the only parthenogenetic lizard known to date in the entire clade Iguanidae (pleurodonta). Our results show that a significant fraction of the transcriptome contains repeats, however many of these are co-expressed with genes. The implementation of our pipeline in real data allowed the identification of the most abundant transposon families in each tissue. The ERV2, CR1, and SINE3 families were particularly abundant in the liver. A test data set is provided in the ExplorATE package.
Project description:The tetrapod-restricted KRAB-containing zinc finger proteins (KRAB-ZFPs) are essential early embryonic controllers of transposable elements (TEs), which they repress via their cofactor KAP1 and associated effectors through histone and DNA methylation, a process thought to result in irreversible silencing. Using a target-centered functional screen, we matched several murine TEs with their cognate KRAB-ZFP. This revealed an unexpected level of granularity in their interactions, with KRAB-ZFPs recognizing TEs from more than one subfamily, TEs recruiting more than one KRAB-ZFP, and spatially and temporally differential KRAB-ZFP-mediated regulation of TEs and nearby genes. Most importantly, we discovered that the KRAB/KAP1 system controls TEs in adult tissues, in cell culture and in vivo, where they partner up to regulate the expression of cellular genes. Therefore, TEs and KRAB-ZFPs establish widely active transcription networks that regulate not only development but probably also many physiological events. Given the high degree of species-specificity of both TEs and KRAB-ZFPs, these results have important implications for studying and understanding the biology of higher vertebrates, including humans. Analysis of transcriptional profiles of KAP1 or ZFP932/Gm15446 KO cells or tissues, and ZFP932 and Gm15446 ChIPseq in murine ES and C2C12 cells.
Project description:Chromatin accessibility is a hallmark of active regulatory function in the genome and variation of chromatin accessibility across individuals has been shown to contribute to complex traits and disease susceptibility. However, the mechanisms responsible for chromatin variation among different individuals and how this variation contributes to phenotypic diversity remain poorly understood. We examined chromatin accessibility variation in liver tissue from seven strains of adult mice that have phenotypic diversity in response to a high-fat/high-sucrose diet. Remarkably, nearly 40% of the loci with the greatest degree of chromatin variability across the strains are associated with transposable elements (TEs), with evolutionarily younger TEs being particularly enriched for regions of chromatin variation. We found that evolutionary younger and older TEs have differential chromatin accessibility profiles and are enriched for binding sites of different transcription factors, indicating the role of TEs in the evolution of regulatory networks in the liver. We also demonstrate that TE polymorphisms and epigenetic regulation of TEs contribute to regulatory variation across different strains through providing binding sites for liver transcription factors. Intriguingly, variable chromatin loci that are associated with liver metabolism are primarily TE-associated. We demonstrate that TEs contribute to regulatory variation in liver and have downstream effects on metabolism. Our data reveal TEs as a novel and important contributor to regulatory and phenotypic variation in the liver and suggest that regulatory variation at TEs is a major contributor to phenotypic variation in populations. Examination of chromatin accessibility with FAIRE-seq in livers of male mice (A/J, AKR/J, BALB/cJ, C57BL/6J, C3H/HeJ, CBA/J, DBA/2J, BXH2/TyJ, and BXH19/TyJ) fed a high-fat, high-sucrose diet.
Project description:The diversity of small RNA-directed DNA methylation (RdDM) mechanisms have been underestimated due to the nearly complete transcriptional silencing of transposable elements (TEs) in the wild-type reference strains of Arabidopsis thaliana. In plants mutant for the SWI/SNF histone remodeler DDM1, TEs are globally activated due to loss of genome wide heterochromatin condensation. Transcriptionally activated TEs go through additional non-canonical forms of RdDM that are dependent on RNA Polymerase II expression. However, the global targets of the non-canonical RdDM pathway have not been explored. In an attempt to identify and contrast the targets of canonical and expression-dependent non-canonical RdDM, we performed MethylC-seq of genome-wide DNA methylation patterns from several RdDM mutants in either the TE-silent or the TE-active (ddm1) contexts. Arabidopsis wildtype and twenty RdDM pathway mutants
Project description:The LIM domain and tumour suppressor protein Testin (Tes) is downregulated in a variety of human tumours and tumour cell lines. Depending on its conformation, Tes localises to stress fibres and focal adhesions where it forms protein complexes with other members of the actin cytoskeleton, such as zyxin and VASP, and thereby influences cellular processes like cell migration, adhesion or spreading. Tes is a modular protein and Tes variants lacking specific domains, localize to different locations in cells. To better understand the molecular basis of its function, we utilized an interaction proteomics approach combined with pathway analysis. This revealed proteins present in complexes in which Tes participates as a function of its modular structure as well as novel Tes interaction partners. We demonstrate that Tes interacts with a short isoform of the glucocorticoid receptor (GR), independently of the conventional full length GRα, a transcription factor important in regulating cellular metabolism and immune function. Tes also interacts with the focal adhesion protein and GR-coactivator Hic-5. In addition, we found that upon overexpression, Tes and Hic-5 induce opposite effects on cell spreading on a fibronectin matrix.
Project description:Mammalian genomes harbour a large number of transposable elements (TEs) and their remnants. Most TEs are incapable of retrotransposition, however, they have evolved as cis-regulatory elements (CREs), enabling them to recruit host-encoded factors. Understanding the contribution of TEs in the regulation of the mammalian genome is an active area of research. Here we show that the male-specific lethal (MSL) complex-mediated acetylation of histone H4 lysine 16 (H4K16ac) regulates the transcription of TEs. Furthermore, H4K16ac marked TEs function as a rich source of cis regulatory elements in the human genome, wherein H4K16ac acts by maintaining the permissive chromatin structure and promoting the transcription of these TEs.
Project description:Mammalian genomes harbour a large number of transposable elements (TEs) and their remnants. Most TEs are incapable of retrotransposition, however, they have evolved as cis-regulatory elements (CREs), enabling them to recruit host-encoded factors. Understanding the contribution of TEs in the regulation of the mammalian genome is an active area of research. Here we show that the male-specific lethal (MSL) complex-mediated acetylation of histone H4 lysine 16 (H4K16ac) regulates the transcription of TEs. Furthermore, H4K16ac marked TEs function as a rich source of cis regulatory elements in the human genome, wherein H4K16ac acts by maintaining the permissive chromatin structure and promoting the transcription of these TEs.
Project description:We study the relatively unexplored evolutionary consequences of the epigenetic effects of transpoable elements (TEs) by providing the first genome-wide quantification of such effects in wild-derived D. melanogaster and D. simulans strains. Surprisingly, over half of euchromatic TEs show spread of repressive epigenetic marks to nearby DNA, resulting in differential epigenetic states of homologous genic alleles and, in return, selection against TEs. Interestingly, compared to D. melanogaster, the lower TE content in D. simulans is correlated with stronger epigenetic effects of TEs and higher levels of host genetic factors known to promote epigenetic silencing. We conclude that the epigenetic effects of euchromatic TEs, and host genetic factors modulating such effects, play a critical role in the population dynamics of TEs within and between species.
Project description:In the male mouse germline, PIWI-interacting RNAs (piRNAs), bound by the PIWI protein MIWI2 (PIWIL4), guide the DNA methylation of young active transposable elements (TEs) through SPOCD1.