Project description:The analysis of stem cell hierarchies in human cancers has been hampered by the impossibility of identifying or tracking tumor cell populations in an intact environment. To overcome this limitation, we devised a strategy based on editing the genomes of patient-derived tumor organoids using CRISPR/Cas9 technology to integrate reporter cassettes at desired marker genes. As proof of concept, we engineered human colorectal cancer (CRC) organoids that carry EGFP and lineage-tracing cassettes knocked in the LGR5 locus. Analysis of LGR5-EGFP+ cells isolated from organoid-derived xenografts demonstrated that these cells express a gene program similar to that of normal intestinal stem cells and that they propagate the disease to recipient mice very efficiently. Lineage-tracing experiments showed that LGR5+ CRC cells self-renew and generate progeny over long time periods that undergo differentiation toward mucosecreting- and absorptive-like phenotypes. These genetic experiments confirm that human CRCs adopt a hierarchical organization reminiscent of that of the normal colonic epithelium. The strategy described herein may have broad applications to study cell heterogeneity in human tumors.
Project description:The CRISPR/Cas genome editing approach in non-model organisms poses challenges that remain to be resolved.Here, we demonstrated a generalized roadmap for a de-novo genome-annotation approach applied to the non-model organism Macrobrachium rosenbergii. We also addressed typical genome editing challenges arising from genetic variations, such as a high frequency of single nucleotide polymorphisms, differences in sex chromosomes, and repetitive sequences that can lead to off-target events. For genome editing of M. rosenbergii, our laboratory recently adapted the CRISPR/Cas genome-editing approach to embryos and embryonic primary cell culture. In this continuation study, an annotation pipeline was trained to predict gene models by leveraging available genomic, transcriptomic, and proteomic data, enabling accurate gene prediction and guide design for knock-outs. Next-generation sequencing analysis demonstrated a high frequency of genetic variations in genes on both autosomal and sex chromosomes, which have been shown to affect the accuracy of editing analyses. To enable future applications based on the CRISPR/Cas tool in non-model organisms, we also verified the reliability of editing efficiency and tracked off-target frequencies. Despite the lack of comprehensive information on non-model organisms, this study provides an example of the feasibility of selecting and editing specific genes with a high degree of certainty.
Project description:Epidermolysis Bullosa Simplex (EBS) is the most common form of Epidermolysis Bullosa (EB) and it is mainly inherited in an autosomal dominant manner (prevalence 1/30000 – 1/50000). Several clinical variants have been described based on the mutated gene, the site of blister formation and the anatomical distribution, but the vast majority of the patients display dominant mutations in genes encoding keratin 5 (KRT5) and keratin 14 (KRT14). The lack of functional keratin intermediate filaments causes basal keratinocytes to exhibit a dramatic cytoplasmatic softening and rupture, when subjected to minor mechanical traction, leading to the distinctive EBS patients intraepidermal blisters formation. Whilst viral mediated addition of a corrected copy of the altered gene is the ascertained approach to tackle recessively inherited EB (such as Junctional and Dystrophic EB), a potential successful combined cell and gene therapy for EBS dominant forms requires the editing of the mutated gene. In this case study, we outlined an allele specific CRISPR/Cas9 gene editing approach able to specifically detect and disrupt a de novo monoallelic c.475/495del21 mutation within exon 1 of KRT14. Taking advantage of the tailored CRISPR/Cas9 system to induce a NHEJ mediated frameshift mutations introduction, we attained a remarkable mutant allele knock-out efficiency. Following KRT14 mutant allele specific gene editing, patient derived primary keratinocytes (EBS01) restored a normal intermediate filament network and mechanical stress resilience.
Project description:Epidermolysis Bullosa Simplex (EBS) is the most common form of Epidermolysis Bullosa (EB) and it is mainly inherited in an autosomal dominant manner (prevalence 1/30000 – 1/50000). Several clinical variants have been described based on the mutated gene, the site of blister formation and the anatomical distribution, but the vast majority of the patients display dominant mutations in genes encoding keratin 5 (KRT5) and keratin 14 (KRT14). The lack of functional keratin intermediate filaments causes basal keratinocytes to exhibit a dramatic cytoplasmatic softening and rupture, when subjected to minor mechanical traction, leading to the distinctive EBS patients intraepidermal blisters formation. Whilst viral mediated addition of a corrected copy of the altered gene is the ascertained approach to tackle recessively inherited EB (such as Junctional and Dystrophic EB), a potential successful combined cell and gene therapy for EBS dominant forms requires the editing of the mutated gene. In this case study, we outlined an allele specific CRISPR/Cas9 gene editing approach able to specifically detect and disrupt a de novo monoallelic c.475/495del21 mutation within exon 1 of KRT14. Taking advantage of the tailored CRISPR/Cas9 system to induce a NHEJ mediated frameshift mutations introduction, we attained a remarkable mutant allele knock-out efficiency. Following KRT14 mutant allele specific gene editing, patient derived primary keratinocytes (EBS01) restored a normal intermediate filament network and mechanical stress resilience.
Project description:CRISPRs and TALENs are efficient systems for gene editing in many organisms including plants. In many cases the CRISPR-Cas or TALEN modules are expressed in the plant cell only transiently. Theoretically, transient expression of the editing modules should limit unexpected effects compared to stable transformation. However, very few studies have measured the off-target and unpredicted effects of editing strategies on the plant genome, and none of them have compared these two major editing systems. We conducted a comprehensive genome-wide investigation of off-target mutations using either a CRISPR-Cas9 or a TALEN strategy. We observed a similar number of SNVs and InDels for the two editing strategies compared to control non-transfected plants, with an average of 8.25 SNVs and 19.5 InDels for the CRISPR-edited plants, and an average of 17.5 SNVs and 32 InDels for the TALEN-edited plants. Interestingly, a comparable number of SNVs and InDels could be detected in the PEG-treated control plants. This shows that except for the on-target modifications, the gene editing tools used in this study did not show a significant off-target activity nor unpredicted effects on the genome, and that the PEG treatment in itself was probably the main source of mutations found in the edited plants.
Project description:Adenosine to Inosine (A-to-I) RNA editing is a site-specific modification of RNA transcripts, catalyzed by members of the ADAR (Adenosine Deaminase Acting on RNA) protein family. RNA editing occurs in human RNA in thousands of different sites. Some of the sites are located in protein-coding regions but the majority is found in non-coding regions, such as 3âUTRs, 5âUTRs and introns - mainly in Alu elements. While editing is found in all tissues, the highest levels of editing are found in the brain. It was shown that editing levels within protein-coding regions are increased during embryogenesis and after birth and that RNA editing is crucial for organism viability as well as for normal development. In this study we characterized the A-to-I RNA editing phenomenon during neuronal and spontaneous differentiation of human embryonic stem cells (hESCs). We identified high editing levels of Alu repetitive elements in hESCs and demonstrated a global decrease in editing levels of non-coding Alu sites when hESCs are differentiating, particularly into the neural lineage. Using RNA interference, we showed that the elevated editing levels of Alu elements in undifferentiated hESCs are highly dependent on ADAR1. DNA microarray analysis showed that ADAR1 knockdown has a global effect on gene expression in hESCs and leads to a significant increase in RNA expression levels of genes involved in differentiation and development processes, including neurogenesis. Taken together, our data suggest that A-to-I editing of Alu sequences plays a role in the regulation of hESC early differentiation decisions. Two samples, One control and the second treated
Project description:Data for the manuscript Casirati et al. "Epitope Editing of Hematopoietic Stem Cells Enables Adoptive Immunotherapies for Acute Myeloid Leukemia"