CRISPR/Cas9-Mediated Correction of the Sickle Mutation in Human CD34+ cells.

Targeted genome editing technology can correct the sickle cell disease mutation of the ß-globin gene in hematopoietic stem cells. This correction supports production of red blood cells that synthesize normal hemoglobin proteins. Here, we demonstrate that Transcription Activator-Like Effector Nucleases (TALENs) and the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 nuclease system can target DNA sequences around the sickle-cell mutation in the ß-globin gene for site-specific cleavage and facilitate precise correction when a homologous donor template is codelivered. Several pairs of TALENs and multiple CRISPR guide RNAs were evaluated for both on-target and off-target cleavage rates. Delivery of the CRISPR/Cas9 components to CD34+ cells led to over 18% gene modification in vitro. Additionally, we demonstrate the correction of the sickle cell disease mutation in bone marrow derived CD34+ hematopoietic stem and progenitor cells from sickle cell disease patients, leading to the production of wild-type hemoglobin. These results demonstrate correction of the sickle mutation in patient-derived CD34+ cells using CRISPR/Cas9 technology.

Reactivating Fetal Hemoglobin Expression in Human Adult Erythroblasts Through BCL11A Knockdown Using Targeted Endonucleases.

We examined the efficiency, specificity, and mutational signatures of zinc finger nucleases (ZFNs), transcriptional activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 systems designed to target the gene encoding the transcriptional repressor BCL11A, in human K562 cells and human CD34+ progenitor cells. ZFNs and TALENs were delivered as in vitro transcribed mRNA through electroporation; CRISPR/Cas9 was codelivered by Cas9 mRNA with plasmid-encoded guideRNA (gRNA) (pU6.g1) or in vitro transcribed gRNA (gR.1). Analyses of efficacy revealed that for these specific reagents and the delivery methods used, the ZFNs gave rise to more allelic disruption in the targeted locus compared to the TALENs and CRISPR/Cas9, which was associated with increased levels of fetal hemoglobin in erythroid cells produced in vitro from nuclease-treated CD34+ cells. Genome-wide analysis to evaluate the specificity of the nucleases revealed high specificity of this specific ZFN to the target site, while specific TALENs and CRISPRs evaluated showed off-target cleavage activity. ZFN gene-edited CD34+ cells had the capacity to engraft in NOD-PrkdcSCID-IL2Rγnull mice, while retaining multi-lineage potential, in contrast to TALEN gene-edited CD34+ cells. CRISPR engraftment levels mirrored the increased relative plasmid-mediated toxicity of pU6.g1/Cas9 in hematopoietic stem/progenitor cells (HSPCs), highlighting the value for the further improvements of CRISPR/Cas9 delivery in primary human HSPCs.

Bioluminescence imaging of angiogenesis in a murine orthotopic pancreatic cancer model.

PURPOSE: Angiogenesis is essential for physiological processes as well as for carcinogenesis. New approaches to cancer therapy include targeting angiogenesis. One target is VEGF-A and its receptor VEGFR2. In this study, we sought to investigate pancreatic cancer angiogenesis in a genetically modified VEGFR2-luc-KI mouse. PROCEDURES: Live in vivo bioluminescence imaging of angiogenesis was performed continuously until sacrifice in subcutaneous tumors as well as in orthotopically transplanted tumors. Tumor tissue was immunostained for CD-31 and VEGFR2. RESULTS: Peritumoral angiogenesis measured by light emission was detected beginning at week 3 following subcutaneous injection. In the orthotopic model, light emission began at day 4, which likely corresponds to wound healing, and continued throughout the experimental period during tumor growth. Peritumoral CD-31 vessel- and VEGFR2-staining were positive. CONCLUSIONS: The VEGFR2-luc-KI mouse is a valuable tool to demonstrate tumor angiogenesis and seems to be suitable to evaluate anti-angiogenic approaches in pancreatic cancer.