The Institute for Basic Science (IBS) research team (Center for Genome Engineering) has successfully confirmed that CRISPR-Cas9 has accurate on-target effects in human cells. This result was achieved through joint research with the Seoul National University College of Medicine and ToolGen, Inc. There has been great interest in CRISPR-Cas9 as a tool to develop anti-cancer cell therapies and/or to correct genetic defects that cause hereditary xxxx in stem and somatic cells. However, because there has been no reliable and sensitive method to measure the accuracy of CRISPR-Cas9 genome-wide, its safety has remained in question. Consequently, it has been difficult to eliminate the possibility that CRISPR-Cas9 may induce mutations in off-target sequences that are similar to on-target sequences. Off-target mutations in tumor suppressor genes, for example, can cause cancer. The researchers have developed a technique termed “Digenome-Seq” to locate both on-target and off-target sequences that can be mutated by CRISPR-Cas9 via genome sequencing. The scientists digested human genomic DNA using Cas9 nucleases in a test tube. This digested DNA was then subjected to whole-genome sequencing. This in vitro digest yielded a unique pattern at both on-target and off-target sequences that can be computationally identified. Furthermore, by adding guanine nucleotides at the end of sgRNA (single-guided RNA) that composes CRISPR-Cas9, they have successfully created this highly-developed programmable nuclease, which has no measurable off-target effects in the human genome. Dr. Jin-Soo Kim, Director of the Center for Genome Engineering at IBS, as well as Professor in the Department of Chemistry at Seoul National University, says, “If CRISPR-Cas9 truncates off-target DNA sequences, it might induce unwanted mutations.
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