Project description:Ectopic expression of the transcription factors Oct4, Sox2, Klf4 and c-Myc (OSKM) can reprogram somatic cells into induced pluripotent stem cells (iPSCs). These iPSCs are highly similar to embryonic stem cells and can be used for regenerative medicine, drug screening and disease modelling. Despite recent advances, reprogramming is a slow and inefficient process. This suggests that there are several safeguarding mechanisms to counteract cell fate conversion. Cellular senescence is one of these barriers, which is mediated through activation of the tumour suppressors p53/p21CIP1, p15INK4b and p16INK4a. In this study, we have screened for shRNAs blunting reprogramming-induced senescence. To evaluate the feasibility of using single-cell RNA Sequencing (scRNA-Seq) in functional screens for simultaneous transcriptome and shRNA identification, we first assessed the accuracy of detecting shRNAs in single cells. To this end we performed a pilot experiment on a pool of OSKM-expressing IMR90 cells infected with the shRNA library.
Project description:To identify genes required for anti-proliferative function of p53 we performed genome-wide and p53TARGET screens in SJSA cells treated with Nutlin.
Project description:RNAi screens via pooled short hairpin RNAs (shRNAs) have recently become a powerful tool for the identification of essential genes in mammalian cells. We synthesized DNA microarrays with six overlapping 25 nt long tiling probes complementary to each unique 60 nt molecular barcode sequence associated with every shRNA expression construct.. In this part of the study pooled shRNAs were transduced into MDA-MB-231 breast carcinoma cell lines and their inhibitory effects four weeks post transduction were analyzed via microarray hybridization.
Project description:To identify factors preferentially necessary to drive tumor expansion we performed parallel in vitro and in vivo negative selection shRNA screens. Melanoma cells harboring shRNAs targeting several DNA Damage Response (DDR) kinases had a greater selective disadvantage in vivo than in vitro, indicating an essential contribution of these factors during tumor expansion. In growing tumors, DDR kinases were activated following hypoxia. Correspondingly, depletion or pharmacologic inhibition of DDR kinases was toxic to melanoma cells, including those that were resistant to BRAF inhibitor, and this could be enhanced by angiogenesis blockade. These results reveal that hypoxia sensitizes melanomas to targeted inhibition of the DDR and illustrate the utility of in vivo shRNA dropout screens for identification of pharmacologically tractable targets. A lentivirus-based kinome shRNA library (four pools) was used to transduce 888mel cells (MOI<0.2). After puromycin selection (1μg/ml), two reference samples were collected as controls. Next, tumor cells (5x105 per injection) were either injected s.c. into 6 NSG mice or plated into 6 independent plates (5x105) for in vitro culture. Tumors were removed from the mice and genomic DNA used to recover shRNAs by PCR amplification followed by deep sequencing. Three analyses were performed independently in parallel: (1) Tumors versus cultured cells (Log2 Fold Change < -1); (2) Tumors versus references (Log2 Fold Change < -2.5) and (3) Cultured cells versus references (Log2 Fold Change < -2.5). Genes targeted with at least 2 shRNAs in each of the analysis were considered hits with an enhanced in vivo effect.
Project description:Large-scale genomic studies have identified multiple somatic aberrations in breast cancer, including copy number alterations, and point mutations. Still, identifying causal variants and emergent vulnerabilities that arise as a consequence of genetic alterations remain major challenges. We performed whole genome shRNA "dropout screens" on 77 breast cancer cell lines. Using a hierarchical linear regression algorithm to score our screen results and integrate them with accompanying detailed genetic and proteomic information, we identify vulnerabilities in breast cancer, including candidate "drivers," and reveal general functional genomic properties of cancer cells. Comparisons of gene essentiality with drug sensitivity data suggest potential resistance mechanisms, effects of existing anti-cancer drugs, and opportunities for combination therapy. Finally, we demonstrate the utility of this large dataset by identifying BRD4 as a potential target in luminal breast cancer, and PIK3CA mutations as a resistance determinant for BET-inhibitors. The T0 measurements for the EFM19, HCC1954, HCC38 screens were omitted for technical reasons. T0 measurements, regardless of cell line, represent the initial abundance of shRNAs before cell line-specific selection effects, leading to highly correlated T0 measurements across cell lines. Our analyses showed a median correlation of 0.92 between pairs of T0 arrays from different cell lines, compared to correlations of 0.94-0.97 for replicate arrays within a cell line, a median correlation of 0.79 between T1 arrays of different cell lines and median correlation of 0.68 between T2 arrays from different cell lines. As a result, we used to T0 measurements of the MCF7 screen to provide initial shRNA abundance measurements for the HCC1954 and HCC38 screens, and T0 measurements from the SW527 screen to provide initial measurements for the EFM19 screen. Additional formatted data can be found at http://neellab.github.io/bfg/. Code and tutorials for the siMEM algorithm can be found at http://neellab.github.io/simem/.
Project description:4C-seq was performed to assess genomic contacts with the SOX2 protmoter, human neural stem cells with no oncogenic alterations were compared to those with concurrent IDH1-R132H overexpression, P53 shRNA knockdown and ATRX shRNA knockdown.
Project description:To identify factors preferentially necessary to drive tumor expansion we performed parallel in vitro and in vivo negative selection shRNA screens. Melanoma cells harboring shRNAs targeting several DNA Damage Response (DDR) kinases had a greater selective disadvantage in vivo than in vitro, indicating an essential contribution of these factors during tumor expansion. In growing tumors, DDR kinases were activated following hypoxia. Correspondingly, depletion or pharmacologic inhibition of DDR kinases was toxic to melanoma cells, including those that were resistant to BRAF inhibitor, and this could be enhanced by angiogenesis blockade. These results reveal that hypoxia sensitizes melanomas to targeted inhibition of the DDR and illustrate the utility of in vivo shRNA dropout screens for identification of pharmacologically tractable targets.
Project description:To evaluate the effect on gene expression by shRNA-58335, we evaluated gene expression by microarray analysis. Gene expression was measured in Huh-7 cells stably expressing shRNA-58335 or control shRNA after infection with adenovirus expressing p53 (Ad-p53) or LacZ (Ad-LacZ).
Project description:RNAi screens via pooled short hairpin RNAs (shRNAs) have recently become a powerful tool for the identification of essential genes in mammalian cells. We synthesized DNA microarrays with six overlapping 25 nt long tiling probes complementary to each unique 60 nt molecular barcode sequence associated with every shRNA expression construct. By analyzing dilution series of expression constructs we show how our approach allows quantification of shRNA abundance from a pool and how it clearly outperforms the commonly used analysis via the shRNAs half hairpin sequences. In this part of the study one equimolar reference pool and three test pools of varying template concentrations were PCR amplified and hybridized to individual arrays.
Project description:RNAi screens via pooled short hairpin RNAs (shRNAs) have recently become a powerful tool for the identification of essential genes in mammalian cells. We synthesized DNA microarrays with six overlapping 25 nt long tiling probes complementary to each unique 60 nt molecular barcode sequence associated with every shRNA expression construct. By analyzing dilution series of expression constructs we show how our approach allows quantification of shRNA abundance from a pool and how it clearly outperforms the commonly used analysis via the shRNAs half hairpin sequences. In this part of the study one equimolar reference pool and three test pools of varying template concentrations were PCR amplified and hybridized to individual arrays.