Project description:Genome-wide CRISPR/Cas9-based screen to identify anti-proliferative genes during ΔNp63α depletion Overall design: H226 cells transduced with the GeCKOv2 A and B libraries were treated to induce p63 knockdown for 14 days to screen for genes affecting proliferation upon depletion of p63.
Project description:Kiwifruit is an important fruit crop; however, technologies for its functional genomic and molecular improvement are limited. The clustered regulatory interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system has been successfully applied to genetic improvement in many crops, but its editing capability is variable depending on the different combinations of the synthetic guide RNA (sgRNA) and Cas9 protein expression devices. Optimizing conditions for its use within a particular species is therefore needed to achieve highly efficient genome editing. In this study, we developed a new cloning strategy for generating paired-sgRNA/Cas9 vectors containing four sgRNAs targeting the kiwifruit phytoene desaturase gene (AcPDS). Comparing to the previous method of paired-sgRNA cloning, our strategy only requires the synthesis of two gRNA-containing primers which largely reduces the cost. We further compared efficiencies of paired-sgRNA/Cas9 vectors containing different sgRNA expression devices, including both the polycistronic tRNA-sgRNA cassette (PTG) and the traditional CRISPR expression cassette. We found the mutagenesis frequency of the PTG/Cas9 system was 10-fold higher than that of the CRISPR/Cas9 system, coinciding with the relative expressions of sgRNAs in two different expression cassettes. In particular, we identified large chromosomal fragment deletions induced by the paired-sgRNAs of the PTG/Cas9 system. Finally, as expected, we found both systems can successfully induce the albino phenotype of kiwifruit plantlets regenerated from the G418-resistance callus lines. We conclude that the PTG/Cas9 system is a more powerful system than the traditional CRISPR/Cas9 system for kiwifruit genome editing, which provides valuable clues for optimizing CRISPR/Cas9 editing system in other plants.
Project description:CRISPR-Cas9 is an efficient and versatile tool for genome engineering in many species. However, inducible CRISPR-Cas9 editing systems that regulate Cas9 activity or sgRNA expression often suffer from significant limitations, including reduced editing capacity, off-target effects, or leaky expression. Here, we develop a precisely controlled sgRNA expression cassette that can be combined with widely-used Cre systems, termed CRISPR-Switch (SgRNA With Induction/Termination by Cre Homologous recombination). Switch-ON facilitates controlled, rapid induction of sgRNA activity. In turn, Switch-OFF-mediated termination of editing improves generation of heterozygous genotypes and can limit off-target effects. Furthermore, we design sequential CRISPR-Switch-based editing of two loci in a strictly programmable manner and determined the order of mutagenic events that leads to development of glioblastoma in mice. Thus, CRISPR-Switch substantially increases the versatility of gene editing through precise and rapid switching ON or OFF sgRNA activity, as well as switching OVER to secondary sgRNAs.
Project description:The clustered regularly interspaced short palindromic repeats (CRISPR) system has recently been developed into a powerful genome-editing technology, as it requires only two key components (Cas9 protein and sgRNA) to function and further enables multiplex genome targeting and homology-directed repair (HDR) based precise genome editing in a wide variety of organisms. Here, we report a novel and interesting strategy by using the Drosha-mediated sgRNA-shRNA structure to direct Cas9 for multiplex genome targeting and precise genome editing. For multiplex genome targeting assay, we achieved more than 9% simultaneous mutant efficiency for 3 genomic loci among the puromycin-selected cell clones. By introducing the shRNA against DNA ligase IV gene (LIG4) into the sgRNA-shRNA construct, the HDR-based precise genome editing efficiency was improved as more than 2-fold. Our works provide a useful tool for multiplex and precise genome modifying in mammalian cells.
Project description:Rapidly growing genetics and bioinformatics studies provide us with an opportunity to obtain a global view of the genetic basis of traits, but also give a challenge to the function validation of candidate genes. CRISPR/Cas9 is an emerging and efficient tool for genome editing. To construct expression clones for the CRISPR/Cas9, most current methods depend on traditional cloning using Gateway reaction or specific type IIS restriction enzymes and DNA ligation, based on multiple steps of PCR. We developed a system for introducing sgRNA expression cassette(s) directly into plant binary vectors in one step. In this system, one sgRNA expression cassette(s) is generated by an optimized multiplex PCR, in which an overlapping PCR took place. Whilst, two sgRNA expression cassettes were amplified in a single round of PCR. Subsequently, an LR or Golden gate reaction was set up with unpurified PCR product and befitting destination vector. We are able to construct expression clones within 36 h, which greatly improves efficiency and saves cost. Furthermore, the efficiency of this system was verified by an agrobacterium-mediated genetic transformation in rice. The system reported here provides a much more efficient and simpler procedure to construct expression clones for CRISPR/Cas9-mediated genome editing.
Project description:SaCas9/sgRNA, derived from Staphylococcus aureus, is an alternative system for genome editing to Streptococcus pyogenes SpCas9/sgRNA. The smaller SaCas9 recognizes a different protospacer adjacent motif (PAM) sequence from SpCas9. SaCas9/sgRNA has been employed to edit the genomes of Arabidopsis, tobacco and rice. In this study, we aimed to test its potential in genome editing of citrus. Transient expression of SaCas9/sgRNA in Duncan grapefruit via Xcc-facilitated agroinfiltration showed it can successfully modify CsPDS and Cs2g12470. Subsequently, binary vector GFP-p1380N-SaCas9/35S-sgRNA1:AtU6-sgRNA2 was developed to edit two target sites of Cs7g03360 in transgenic Carrizo citrange. Twelve GFP-positive Carrizo transformants were successfully established, designated as #Cz1 to #Cz12. Based on targeted next generation sequencing results, the mutation rates for the two targets ranged from 15.55 to 39.13% for sgRNA1 and 49.01 to 79.67% for sgRNA2. Therefore, SaCas9/sgRNA can be used as an alternative tool to SpCas9/sgRNA for citrus genome editing.
Project description:Probiotics and antibiotics are widely used in poultry and may alter drug bioavailability by affecting the expression of intestinal ATP-binding cassette (ABC) efflux transporters. Therefore the aim of the present investigation was to evaluate the effect of Lactobacilli probiotics, administered alone or in combination with doxycycline, on the expression of ABCB1 (gene, encoding P-glycoprotein), ABCC2 (gene, encoding multidrug resistance protein 2, MRP2) and ABCG2 (gene, encoding breast cancer resistance protein) mRNAs in chicken using RT-PCR. Duc one-day-old chicks (n=24) were divided equally in four groups: untreated control, probiotics supplemented group, probiotics plus doxycycline treated chickens and antibiotic administered group. Expression of ABCC2 mRNA was affected by doxycycline or by combination of Lactobacillus plantarum, L. brevis and L. bulgaricus and the antibiotic in the intestines. These results can be used as a basis for further functional studies to prove the beneficial effect on limitation of the absorption of toxins and improvement of efflux of endogenous substances and xenobiotics when the combination of doxycycline and Lactobacillus spp. probiotics are administered to poultry.
Project description:The effective application of the clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 system in biology, medicine and other fields is hindered by the off-target effects and loci-affinity of Cas9-sgRNA, especially at a genome-wide scale. In order to eliminate the occurrence of off-target effects and evaluate loci-affinity by CRISPR/Cas9 site-specific detection and screening of high-affinity sgRNA sequences, respectively, we develop a CRISPR/Cas9-assisted reverse PCR method for site-specific detection and sgRNA sequence validation. The detection method based on PCR can be used directly in the laboratory with PCR reaction conditions, without the need for an additional detection system, and the whole process of detection can be completed within 2 h. Therefore, it can be easily popularized with a PCR instrument. Finally, this method is fully verified by detecting multiple forms of site mutations and evaluating the affinity of a variety of sgRNA sequences for the CRISPR/Cas9 system. In sum, it provides an effective new analysis tool for CRISPR/Cas9 genome editing-related research. A CRISPR/Cas9-assisted reverse PCR method was developed for Cas9/sgRNA site-specific detection and sgRNA sequence validation. The technique detects target DNA in three steps: (1) target DNA is specifically cut by a pair of Cas9/sgRNA complexes; (2) the cleaved DNA is rapidly linked by T4 DNA ligase; (3) the ligated DNA is efficiently amplified by PCR (PCR or qPCR).