L1 retrotransposition in human iPSCs
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Project description:L1 retrotransposons are active elements in the genome, capable of mobilization in neuronal progenitor cells. Previously, we showed that chromatin remodeling during neuronal differentiation allows for a transient stimulation of L1 transcription. The activity of L1 retrotransposons during brain development can impact gene expression and neuronal function. Here we show that L1 neuronal retrotransposition in rodents is increased in the absence of MeCP2, a protein involved in global methylation and human neurodevelopmental diseases. Using neuronal progenitor cells derived from human induced pluripotent stem cells and human tissues, we revealed that Rett syndrome patients, with MeCP2 mutations, have increased susceptibility for L1 retrotransposition. Our data demonstrate that disease-related genetic mutations can influence the frequency of neuronal L1 retrotransposition, thereby increasing brain-specific genetic mosaicism. Genetic reprogramming of somatic cells to a pluripotent state (induced pluripotent stem cells, or iPSCs) by over-expression of specific genes has been accomplished for fibroblasts derived from controls and Rett syndrome patients. Different clones from each were compared to respective original fibroblasts and a human embryonic stem cell line. Gene expression profiles measured using human genome Affymetrix Gene Chip arrays were grouped by hierarchical clustering, and correlation coefficients were computed for all pair-wise comparisons.
2010-11-11 | E-GEOD-21037 | biostudies-arrayexpress
Project description:Somatic L1 retrotransposition events have been shown to occur in epithelial cancers1-8. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases, but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds and many were present in multiple tumor sections implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth. Here we show Human SNP 6.0 Array experiments on DNAs from four colorectal cancer patients (1BV, 2BV, 3BV, and 4BV) with polyps and metastases. Here we characterize the samples for CNVs and compare the samples' CNV status to their respective somatic L1 retrotransposition profile.
2015-08-10 | E-GEOD-63601 | biostudies-arrayexpress
Project description:L1 retrotransposons are active elements in the genome, capable of mobilization in neuronal progenitor cells. Previously, we showed that chromatin remodeling during neuronal differentiation allows for a transient stimulation of L1 transcription. The activity of L1 retrotransposons during brain development can impact gene expression and neuronal function. Here we show that L1 neuronal retrotransposition in rodents is increased in the absence of MeCP2, a protein involved in global methylation and human neurodevelopmental diseases. Using neuronal progenitor cells derived from human induced pluripotent stem cells and human tissues, we revealed that Rett syndrome patients, with MeCP2 mutations, have increased susceptibility for L1 retrotransposition. Our data demonstrate that disease-related genetic mutations can influence the frequency of neuronal L1 retrotransposition, thereby increasing brain-specific genetic mosaicism.
2010-11-11 | GSE21037 | GEO
Project description:We report that TAR DNA binding protein 43 (TDP-43), mutations in which constitute a major risk factor for amyotrophic lateral sclerosis (ALS), inhibits L1 retrotransposition in mouse embryonic stem cells (mESCs) and preimplantation embryos. Knockdown of TDP-43 resulted in massive genomic L1 expansion and impaired cell growth in preimplantation embryos and ESCs. Functional analysis demonstrated that TDP-43 interacts with L1 open reading frame 1 protein (L1 ORF1p) to mediate genomic protection, and loss of this interaction led to de-repression of L1 retrotransposition. Our results identify TDP-43 as a guardian of the embryonic genome by protecting it from massive L1 retrotransposition.
2023-01-04 | GSE199197 | GEO
Project description:Somatic L1 retrotransposition events have been shown to occur in epithelial cancers1-8. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases, but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds and many were present in multiple tumor sections implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth. We assessed the impact of somatic L1 insertions on the expression of the corresponding protein-coding genes by comparing protein abundance in the polyp with the highest number of somatic L1 insertions with that of its paired normal colon using mass spectrometry analysis. Of the 10 validated somatic insertions that were in protein coding regions in the polyp, two proteins – KIAA1217 and WARS2 – were downregulated in the adenoma >90% and >70%, respectively.
2015-08-11 | PXD001626 | Pride
Project description:Somatic L1 Retrotransposition of Colorectal Tumors
| PRJNA173389 | ENA
Project description:Somatic L1 retrotransposition events have been shown to occur in epithelial cancers1-8. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases, but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds and many were present in multiple tumor sections implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth.
2015-08-10 | GSE63601 | GEO
Project description:Transposable elements (TEs) are now recognized not only as parasitic DNA, whose spread in the genome must be controlled by the host, but also as major players in shaping genome evolution and providing genetic substrates for evolving new regulatory functions. Long INterspersed Element-1 (LINE-1 or L1), the only currently autonomous mobile transposon in humans, occupies 17% of the genome and continues to generate inter- and intra-individual genetic variation, in some cases resulting in disease. Nonetheless, our knowledge of how L1 activity is controlled and what function L1s play in host gene regulation remains fragmentary. Here, we use CRISPR/Cas9 screening strategies in two distinct human cell lines to provide the first genome-wide survey of genes involved in L1 retrotransposition control. Through this approach we identified functionally diverse genes that either promote or restrict L1 retrotransposition. These factors control the L1 life cycle at transcriptional or post-transcriptional levels, and in a manner which in some, but not in other cases depends on the endogenous L1 sequence, underscoring the complexity of L1 regulation. We further investigated L1 restriction by three candidate regulators, MORC2 and HUSH (human silencing hub) complex subunits TASOR and MPP8. HUSH/MORC2 selectively bind evolutionarily young, full-length L1s immersed within transcriptionally permissive euchromatic environment, and promote H3K9me3 deposition for transcriptional silencing. Interestingly, these silencing events often occur within introns of transcriptionally active host genes, and lead to down-regulation of host gene expression in a HUSH/MORC2-dependent manner. Together, our data provide a rich resource for studies of L1 retrotransposition, elucidate a novel L1 restriction pathway, and illustrate how epigenetic silencing of TEs can influence host gene expression programs.
2017-12-06 | GSE95374 | GEO
Project description:We used ATLAS-seq-neo to map the sites of integration of an engineered LINE-1 (L1) retrotransposon into the genome of HeLa S3 cells. In brief, we transfected cells with a plasmid-borne L1.3 element carrying a neomycin-resistance-based retrotransposition cassette, as well as a hygromycin-resistance cassette on the plasmid backbone. For this set of experiments, cells were only selected for transfection (hygromycin) but not for retrotransposition (neomycin). Then we prepared ATLAS-seq-neo libraries. Each sample corresponds to an independent transfection and pool of hygromycin-resistant cells. ATLAS-seq-neo relies on the random mechanical fragmentation of the genomic DNA to ensure high-coverage, ligation of adapter sequences, suppression PCR-amplification of the 3' end L1 junction with its flanking genomic sequence, and Ion Torrent sequencing using single-end 400 bp read chemistry. The primer used for suppression PCR specifically targets the engineered element and not endogenous copies as in the original ATLAS-seq protocol (Philippe et al. eLife 2016). For some libraries, the linker-ligated genomic DNA was digested with BamHI, which cuts downstream of L1 polyA site in the plasmid backbone, to limit amplification from the plasmid and enrich for retrotransposition-mediated insertion events into the genomic DNA.
2019-04-03 | E-MTAB-7644 | biostudies-arrayexpress
Project description:Understanding cellular and molecular differences between human and non-human primates (NHPs) is essential to the basic comprehension of the evolution and diversity of our own species. Until now, preserved tissues have been the main source of most comparative studies between humans, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). However, these tissue samples do not fairly represent the distinctive traits of live cell behavior, are not amenable to genetic manipulation and do not allow translation of observed differences into phenotypical divergence. We hypothesized that induced pluripotent stem cells (iPSCs) could provide a unique biological resource to elucidate relevant phenotypical differences between human and the great apes and that those differences could have potential adaptation and speciation value. Here, we describe the generation and initial characterization of iPSCs from chimpanzees and bonobos as novel tools to explore our most recent evolution. Comparative gene expression analysis of human and NHP iPSCs revealed differences in regulation of Long Interspersed Nuclear Element (LINE-1 or L1) transposons. A force of change in mammalian evolution, L1 elements are retrotransposons that have remained active during primate evolution. We observed decreased levels of L1 restricting factors APOBEC3B (A3B)7 and PIWIL28 in NHP iPSCs which was correlated with increased human and chimpanzee L1 mobility and endogenous L1 mRNA levels. Moreover, results from manipulation of A3B and PIWIL2 levels in iPSCs suggested a causal inverse relationship between levels of these proteins and L1 activity. Finally, we found increased copy numbers of species-specific L1 elements in the genome of chimpanzees compared to humans, supporting the idea that increased L1 mobility in NHPs is not limited to iPSCs in culture and may have also occurred in the germline during primate evolution. We propose that differences in L1 mobility may have differentially shaped the genomes of humans and NHPs and could have had an adaptive significance. polyA RNA-Seq profiling of iPS cells from human, chimpanzee, and bonobo, and small RNA-Seq profiling of human iPS cells.
2013-10-23 | E-GEOD-47626 | biostudies-arrayexpress