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That crisp new CRISPR feeling
As many of you already know from reading this commentary section each month, we have several Special Focus sections planned this year for cancer research news, the first having already appeared in February. As pleased as we are to bring you those—after all, oncology-related drug discovery and development has perhaps been the most vigorous and dynamic area going for some years now—we are also very excited to bring you two Special Focus sections on CRISPR developments and advances, one next month and one in September. CRISPR has already opened a great many potential research and therapeutic windows and promises much more in the future.
I’ve been gathering material for both CRISPR sections already and will gather more, but by way of an appetizer—and because there is so much going on right now—I wanted to share a few items that might be “old” even for next month for a special feature section (having happened on the cusp of summer/fall last year), but are still “evergreen” enough to be relevant and useful for you, the DDNews reader.
A fix for sickle cell?
Scientists led by researchers at St. Jude Children’s Research Hospital have used CRISPR gene editing to help fix sickle cell disease and beta-thalassemia in blood cells isolated from patients, reporting their results in a study that appeared last year in Nature Medicine.
“Our work has identified a potential DNA target for genome editing-mediated therapy and offers proof of principle for a possible approach to treat sickle cell and beta-thalassemia,” said Dr. Mitchell J. Weiss, chair of the St. Jude Department of Hematology and one of the study’s lead authors. “We have been able to snip that DNA target using CRISPR, remove a short segment in a ‘control section’ of DNA that stimulates gamma-to-beta switching and join the ends back up to produce sustained elevation of fetal hemoglobin levels in adult red blood cells.”
When the scientists edited the DNA of blood-forming stem cells derived from patients with sickle cell disease, they were able to activate those genes and produce red blood cells that had enough fetal hemoglobin to be healthy.
Getting the most from the yeast
Researchers at Synthetic Genomics and the J. Craig Venter Institute wrote in a study published August in Scientific Reports that they had created a yeast-based platform for editing bacterial genomes using CRISPR/Cas9, engineering the small ribosomal subunit (16s) RNA of Mycoplasma mycoides, a gene considered essential for cell viability.
“In bacteria, rational mutagenesis of essential genes, often involved in fundamental biological process, is seldom accomplished in an efficient manner directly on the chromosome,” the authors noted, adding that with their genome-editing platform, they were able to get “robust and extensive site-directed mutagenesis directly on the bacterial chromosome with up to 100-percent efficiency.”
Commented Krishna Kannan, an author on the paper: “This new genomic platform would allow us to quickly engineer any essential gene in the ‘simplest’ M. mycoides genome and obtain a quick, binary ‘yes’ or ‘no’ answer as to whether the modification introduced could support cellular viability.”
Guide RNA libraries created from mRNA
Research from the Italian Foundation for Cancer Research’s Institute of Molecular Oncology indicates that expressed mRNA can be turned into guide RNAs for CRISPR/Cas9 knockout screens.
Study author Hiroshi Arakawa wrote in a paper, published in Science Advances, “This method does not rely on bioinformatics and opens a path for forward genetics screening of any species, independent of their genetic characterization,” adding that the method was able to generate multiple guide sequences for the same gene. This can be critical in CRISPR/Cas9 knockout screens because they may have several different gRNAs for each gene.
“It can be also useful to make personalized human gRNA libraries, which represent collections of single-nucleotide polymorphisms from different exons,” Arakawa noted. “These personalized human gRNA libraries could be used to study allelic variations and their phenotypes, leading to better characterizations of rare diseases.”