Gene editing fixes harmful mutation in human embryos

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- Researchers in OR have announced that they have successfully altered genes in a human embryo for the first time in the United States, but Catholic ethicists warn that the procedure was morally objectionable for many reasons.

In their new paper, a consortium of scientists in California, Oregon and Asia detailed using the genome-editing technique CRISPR to fix DNA that causes a common genetic heart disease known as hypertrophic cardiomyopathy.

They targeted a gene mutation that causes a heart-weakening disease, hypertrophic cardiomyopathy, that affects about 1 in 500 people.

Amato, Shoukhrat and a team studied a gene mutation which causes hypertrophic cardiomyopathy, a hereditary disease of the heart muscle which can translate into sudden heart failure and death, notably in athletes.

Their research was published Wednesday, Aug. 2, in the journal 'Nature.' It demonstrates a new method of repairing a disease-causing mutation and preventing it from being inherited by succeeding generations.

There have been other successful attempts to edit human embryos carried out by scientists in China, but those experiments revealed errors in CRISPR's ability to seamlessly edit DNA.

CRISPR-Cas9 uses guide-RNA molecules to target and cut specific segments of DNA.

At present, South Korea's ethical guidelines ban experimenting on human embryos in the country. But Mitalipov and colleagues explicitly conducted the experiments to improve the safety and efficiency of gene editing for eventual clinical trials, which would involve implanting edited embryos into women's uteruses to establish pregnancy.

Then came the test. Researchers injected sperm from a patient with the heart condition along with those molecular scissors into healthy donated eggs at the same time.

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An worldwide team of scientists completed a groundbreaking experiment on Wednesday, successfully eliminating a genetic disease by editing human embryos.

The researchers found that 72.4 percent of the embryos, not 50 percent as would have been expected, were free of the errant gene.

The researchers broke the mutated gene using a technology called CRISPR-Cas9. Natural DNA-repair mechanisms in the cell follow up by filling in the missing pieces. They applied CRISPR at the earliest stage possible-when the embryo is still a single cell-to ensure that the genetic changes they introduced were propagated to every cell of the embryo as it divided and developed.

Mitalipov hopes that their technique could one day be used to treat a wide-range of genetic diseases and save the lives of millions of people.

It's now illegal in the USA and many countries to implant a gene-edited embryo into a mother's womb to produce a baby. Not only did a high percentage of embryonic cells get repaired, but also gene correction didn't induce any detectable off-target mutations and genome instability - major concerns for gene editing.

In this case, scientists can analyze the embryos in vitro to weed out any with the genetic defect before implantation into the womb.

Instead, the newly forming embryos made their own ideal fix without that outside help, reported Oregon Health & Science University senior researcher Shoukhrat Mitalipov.

Earlier this year, an ethics report from the prestigious National Academy of Sciences opened the door to lab research to figure out how to make such changes - but said if germline editing ever is allowed, it should be reserved for serious diseases with no good alternatives and performed under rigorous oversight.

Asked about critics of genetic manipulation, he said his work has nothing to do with the creation of "designer babies" through genetic manipulation to give the children traits desired by the parents.

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