A powerful “genome editing” technology known as CRISPR has been used by researchers since 2012 to trim, disrupt, replace or add to sequences of an organism’s DNA. Now, scientists at Johns Hopkins Medicine have shown that the system also precisely and efficiently alters human stem cells.
Previous research has shown that CRISPR (third generation gene editing) can generate genomic changes or mutations through these interventions far more efficiently than other gene editing techniques, such as TALEN (2nd generation gene editing) , short for transcription activator-like effector nuclease.
CRISPR 100 times better then TALENS in some efficiency tests
The researchers compared the ability of both genome editing systems to either cut out pieces of known genes in iPSCs or cut out a piece of these genes and replace it with another. As model genes, the researchers used JAK2, a gene that when mutated causes a bone marrow disorder known as polycythemia vera; SERPINA1, a gene that when mutated causes alpha1-antitrypsin deficiency, an inherited disorder that may cause lung and liver disease; and AAVS1, a gene that’s been recently discovered to be a “safe harbor” in the human genome for inserting foreign genes.
Their comparison found that when simply cutting out portions of genes, the CRISPR system was significantly more efficient than TALEN in all three gene systems, inducing up to 100 times more cuts. However, when using these genome editing tools for replacing portions of the genes, such as the disease-causing mutations in JAK2 and SERPINA1 genes, CRISPR and TALEN showed about the same efficiency in patient-derived iPSCs, the researchers report.
Contrary to results of the human cancer cell line study, both CRISPR and TALEN had the same targeting specificity in human iPSCs, hitting only the genes they were designed to affect, the team says. The researchers also found that the CRISPR system has an advantage over TALEN: It can be designed to target only the mutation-containing gene without affecting the healthy gene in patients, where only one copy of a gene is affected.
The findings, together with a related study that was published earlier in a leading journal of stem cell research (Cell Stem Cell), offer reassurance that CRISPR will be a useful tool for editing the genes of human iPSCs with little risk of off-target effects, say Ye and Cheng.
“CRISPR-mediated genome editing opens the door to many genetic applications in biologically relevant cells that can lead to better understanding of and potential cures for human diseases,” says Cheng.
SOURCE – John Hopkins
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