Project description:To investigate the changes in circRNAs expression after SVA infection in PK-15 cells, we established a model of SVA-infected PK-15 cells.
Project description:SVA retrotransposons remain active in humans and contribute to individual genetic variation. Polymorphic SVA alleles harbor gene-regulatory potential and can cause genetic disease. However, how SVA insertions are controlled and functionally impact human disease is unknown. Here, we dissect the epigenetic regulation and influence of SVAs in cellular models of X-linked dystonia-parkinsonism (XDP), a neurodegenerative disorder caused by an SVA insertion at the TAF1 locus. We demonstrate that the KRAB zinc finger protein ZNF91 establishes H3K9me3 and DNA methylation over SVAs, including polymorphic alleles, in human neural progenitor cells. The resulting mini-heterochromatin domains attenuate the cis-regulatory impact of SVAs. This is critical for XDP pathology; removal of local heterochromatin severely aggravates the XDP molecular phenotype, resulting in increased TAF1 intron retention and reduced expression. Our results provide unique mechanistic insights into how human polymorphic transposon insertions are recognized, and their regulatory impact constrained by an innate epigenetic defense system.
Project description:Domestication of transposable elements (TEs) into functional cis-regulatory elements is a widespread phenomenon. However, why some TEs are co-opted as functional enhancers while others are not is underappreciated. SINE-Vntr-Alus (SVAs) are the youngest group of transposons in the human genome, where ~3,700 copies are annotated, nearly half of which are human-exclusive. Many studies indicated that the SVAs are among the most frequently co-opted TEs in human gene regulation, but the mechanisms underlying such process have not yet been thoroughly investigated. Here, we leveraged CRISPR-interference (CRISPRi), computational and functional genomics to elucidate the genomic features that underlie SVA domestication into human stem-cell gene regulation. We found that ~750 SVAs are co-opted as functional cis-regulatory elements in human induced Pluripotent Stem Cells. Co-opted SVAs are significantly closer to genes and harbor more transcription factor binding sites than the not co-opted ones. We show that a long DNA-motif composed of flanking YY1/2 and OCT4 binding sites is enriched in the co-opted SVAs, and that these two factors bind, as predicted, near each other on the TE sequence. Repression of all the ~750 co-opted SVAs by CRISPRi in a line with stem-like properties (NCCIT) led to loss of YY1/OCT4 binding and alteration of neighboring gene expression. Ultimately, SVA repression resulted in ~3,000 differentially expressed genes, 131 of which were the nearest gene to an annotated SVA. In summary, we demonstrated that SVAs contribute significantly to human gene regulation, and that both genomic location and sequence composition contribute to SVA domestication in the gene regulatory networks.
Project description:DNA methylation, repressive histone modifications, and PIWI-interacting RNA are essential for controlling retroelement silencing in the mammalian germ line. Dysregulation of retroelement silencing is associated with male sterility. Although DNA methylation mechanisms have been extensively studied in mouse germ cells, little progress has been made in humans. Here, we show that the Krüppel-associated box domain zinc finger proteins (KRAB-ZFPs) are associated with DNA methylation of retroelements in human primordial germ cells (hPGCs), and hominoid-specific retroelement SINE-VNTR-Alus (SVA) is subjected to transcription-directed de novo DNA methylation during human spermatogenesis. Furthermore, we show that the degree of de novo DNA methylation in SVAs varies among human individuals, which confers a major inter-individual epigenetic variation in sperm. Collectively, our results provide potential molecular mechanisms of how retroelements are regulated during human male germ cells