Successful mutation repair by CRISPR-Cas9 in viable human embryos

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A research team has successfully corrected a genetic mutation in 58 viable human embryos. The groundbreaking work was carried out using the CRISPR-Cas9 gene editing system and targeted the dominant mutation in the MYBPC3 gene.

The MYBPC3 mutation causes the heart muscle to thicken, resulting in a condition called hypertrophic cardiomyopathy, which can be fatal. The team bypassed the usual CRISPR route of inserting the DNA of the Cas9 enzyme into the cell for Cas9 generation thereafter. Instead, the team injected the Cas9 protein itself, bound to its guide RNA, directly into the cells.This was able to allay safety concerns regarding off target mutations and the introduction of unwanted DNA to the cell. Another safety concern was the generation of mosaics; when cells in an embryo contain differing genetic sequences. Only a single instance of this was found in the present study, which could possibly be attributed to the early timing of injection with CRSPR-Cas9 compared to other studies.

The work was carried out at the Oregon Health and Science University in Portland, led by reproductive biologist Shoukhrat Mitalipov, and published in Nature. Despite ethical concerns surrounding the editing of human embryos, the team pointed towards the mechanism by which the mutation was corrected as evidence of distance from the concept of ‘designer babies’. This was because although the team provided a template DNA strand for the rewriting of the mutation, the embryos instead used the mother’s unmutated DNA as a guide for repairing the MYBPC3 mutation, suggesting that ‘you couldn’t add anything that wasn’t already there.’

Source: CRISPR fixes disease gene in viable human embryos Press Release