in Human Embryos, Study Finds

A powerful gene-editing tool called Crispr-Cas9, which this month nabbed the Nobel Prize in Chemistry for two female scientists, can cause serious side effects in the cells of human embryos, prompting them to discard large chunks of their genetic material, a new study has found.

Administered to cells to repair a mutation that can cause hereditary blindness, the Crispr-Cas9 technology appeared to wreak genetic havoc in about half the specimens that the researchers examined, according to a study published in the journal Cell on Thursday.

The consequences of these errors can be quite serious in some cases, said Dieter Egli, a geneticist at Columbia University and an author of the study. Some cells were so flummoxed by the alterations that they simply gave up on trying to fix them, jettisoning entire chromosomes, the units into which human DNA is packaged, Dr. Egli said.

“We’re often used to hearing about papers where Crispr is very successful,” said Nicole Kaplan, a geneticist at New York University who was not involved in the study. “But with the amount of power we hold” with this tool, Dr. Kaplan said, it is crucial “to understand consequences we didn’t intend.”

Crispr-Cas9, a scissorslike chemical tool that can precisely cut and customize stretches of genetic material, such as human DNA, stoked international controversy in 2018 when He Jiankui, a Chinese scientist, used the technology to yield the world’s first gene-edited infants. The experiment was widely condemned as irresponsible and dangerous — in large part because many of the ways in which Crispr-Cas9 can affect cells remain poorly understood. Dr. He was found guilty of conducting illegal medical practices in China and sentenced to three years in prison.

The new paper’s findings further underscore that “it’s really too soon to be applying Crispr to reproductive genetics,” said Nita Farahany, a bioethicist at Duke University who was not involved in the study.

Crispr-Cas9 treatments have already been given directly to people to treat conditions like blindness — a potential cure that affects that patient, and that patient only. But modifications made to sperm, eggs and embryos can be passed to future generations, raising the stakes for any mistakes made along the way.

Fonte: https://www.nytimes.com/2020/10/31/health/crispr-genetics-embryos.html. Adaptado. Acesso em: novembro 2020

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