Project description:To test if LEDGF/p75 influences distribution of Maedi-visna virus (MVV) integration sites, we infected human HEK293T, LKO (PSIP1-null), and LHKO (PSIP1/HDGFL2-null) cells with MVV-derived vector. Genomic DNA was isolated from infected cells, and chromosomal junctions at integrated U5 vDNA ends were amplified using linker-mediated PCR, sequenced using Illumina technology and mapped to human genome.
Project description:To test if LEDGF/p75 influences distribution of Maedi-visna virus (MVV) integration sites, we infected sheep CPT3, LKO1 (PSIP1-null), LHKO1 and LHKO2 (PSIP1/HDGFL2-null) cells with MVV-derived vector. Genomic DNA was isolated from infected cells, and chromosomal junctions at integrated U5 vDNA ends were amplified using linker-mediated PCR, sequenced using Illumina technology and mapped to sheep genome.
Project description:Recombinant adeno-associated virus (AAV)-based vectors are used clinically for gene transfer and persist as extrachromosomal episomes. A small fraction of vector genomes can integrate into the host genome, but the theoretical risk of tumorigenesis may depend on vector regulatory features. A mouse model was used to investigate long-term kinetics and integration profiles of an AAV serotype 5 (AAV5) vector that mimics key features of valoctocogene roxaparvovec (AAV5-hFVIII-SQ), a gene therapy for severe hemophilia A. The majority (95%) of vector genome reads identified by target enrichment sequencing were derived from episomes, and mean integration frequency was 2.70 (standard deviation, 1.24) integrations per 1000 cells. Longitudinal integration analysis suggested AAV5 vector integrations occur primarily within 1 week, at low frequency, and their abundance was stable over time. Integration profiles were polyclonal, and only 5.46% of integrations had a common integration site order ≥5, suggesting random distributions when looking at a 50-kb genomic window. No integrations were associated with clonal expansion. Integrations were enriched near transcription start sites of genes highly expressed in the liver (P = 1x10−4) and less enriched for genes with low or no liver expression. We found no evidence of tumorigenesis or fibrosis caused by the vector integrations.
Project description:Human artificial chromosomes (HACs) have unique characteristics as gene-delivery vector, e.g., episomal transmission and transfer of multiple, large transgenes. Here, we demonstrate the advantages of HAC vectors for reprogramming mouse embryonic fibroblasts (MEFs) to induced pluripotent stem (iPS) cells. Two HAC vectors (iHAC1 and iHAC2) were constructed. Both carried four reprogramming factors, and iHAC2 also encoded a p53-knockdown construct (see Kazuki et al 2011). The iHAC1 partially reprogrammed MEFs, and the iHAC2 efficiently reprogrammed MEFs. Global gene expression showed that the iHACs, unlike other vectors, generated relatively uniform iPS cells. We established iHAC-free iPS cells by isolating cells that spontaneously lost the iHAC2. Analyses of pluripotent markers, teratomas, and chimeras confirmed that these iHAC-free iPS cells were pluripotent. Moreover, iHAC-free iPS cells with a re-introduced HAC encoding Herpes Simplex Virus Thymidine Kinase were eliminated by Ganciclovir treatment; therefore, the HAC safeguard system functioned in iPS cells. Thus, the HAC vector could generate uniform, integration-free iPS cells with a safeguard system.
Project description:The CRISPR-Cas12a platform has attracted interest in the genome editing community because the prototypic Acidaminococcus Cas12a generates a staggered DNA double-strand break upon binding to an AT-rich protospacer-adjacent motif (PAM, 5'-TTTV). The broad application of the platform in primary human cells was enabled by the development of an engineered version of the natural Cas12a protein, called Cas12a Ultra. In this study, we confirmed that CRISPR-Cas12a Ultra ribonucleoprotein complexes enabled allelic gene disruption frequencies of over 90% at multiple target sites in human T cells, hematopoietic stem and progenitor cells (HSPCs), and induced pluripotent stem cells (iPSCs). In addition, we demonstrated for the first time the efficient knock-in potential of the platform in human iPSCs and achieved targeted integration of a GFP marker gene into the AAVS1 safe harbor site and a CSF2RA super-exon into CSF2RA in up to 90% of alleles without selection. Clonal analysis revealed bi-allelic integration in >50% of the screened iPSC clones without compromising their pluripotency and genomic integrity. Thus, in combination with the adeno-associated virus vector system, CRISPR-Cas12a Ultra provides a highly efficient genome editing platform for performing targeted knock-ins in human iPSCs.
Project description:Human artificial chromosomes (HACs) have unique characteristics as gene-delivery vector, e.g., episomal transmission and transfer of multiple, large transgenes. Here, we demonstrate the advantages of HAC vectors for reprogramming mouse embryonic fibroblasts (MEFs) to induced pluripotent stem (iPS) cells. Two HAC vectors (iHAC1 and iHAC2) were constructed. Both carried four reprogramming factors, and iHAC2 also encoded a p53-knockdown construct (see Kazuki et al 2011). The iHAC1 partially reprogrammed MEFs, and the iHAC2 efficiently reprogrammed MEFs. Global gene expression showed that the iHACs, unlike other vectors, generated relatively uniform iPS cells. We established iHAC-free iPS cells by isolating cells that spontaneously lost the iHAC2. Analyses of pluripotent markers, teratomas, and chimeras confirmed that these iHAC-free iPS cells were pluripotent. Moreover, iHAC-free iPS cells with a re-introduced HAC encoding Herpes Simplex Virus Thymidine Kinase were eliminated by Ganciclovir treatment; therefore, the HAC safeguard system functioned in iPS cells. Thus, the HAC vector could generate uniform, integration-free iPS cells with a safeguard system. Total RNA from mouse embryonic fibroblasts, two control ES cells (TT2 and B6ES), retrovirus vector-derived iPS cells (20D17), and twelve HAC-derived iPS clones were hybridized to the Agilent Whole Mouse Genome microarrays.
Project description:Foamy viruses (FVs) or spumaviruses are retroviruses that have been developed as vectors, but their integration patterns have not been described. We have performed a large-scale analysis of FV integration sites in unselected human fibroblasts (n = 1,008) and human CD34(+) hematopoietic cells (n = 1,821) by using a bacterial shuttle vector and a comparable analysis of lentiviral vector integration sites in CD34(+) cells (n = 1,331). FV vectors had a distinct integration profile relative to other types of retroviruses. They did not integrate preferentially within genes, despite a modest preference for integration near transcription start sites and a significant preference for CpG islands. The genomewide distribution of FV vector proviruses was nonrandom, with both clusters and gaps. Transcriptional profiling showed that gene expression had little influence on integration site selection. Our findings suggest that FV vectors may have desirable integration properties for gene therapy applications.