US team safely edits dozens of human embryos to correct disease causing genes

The first known attempt at creating genetically modified human embryos in the United States has been carried out by a team of researchers in Portland, Oregon. Three previous reports of editing human embryos were all published by scientists in China. The US work is believed to have broken new ground both in the number of embryos experimented upon and by demonstrating that it is possible to safely and efficiently correct defective genes that cause inherited diseases.

The US Crispr gene editing has convincingly shown that it is possible to avoid both mosaicism and "off-target" effects, as the CRISPR errors are known.

Mitalipov's group appears to have overcome earlier difficulties by "getting in early" and injecting CRISPR into the eggs at the same time they were fertilized with sperm.

That concept is similar to one tested in mice by Tony Perry of Bath University. Perry successfully edited the mouse gene for coat color, changing the fur of the offspring from the expected brown to white.

Somewhat prophetically, Perry's paper on the research, published at the end of 2014, said, "This or analogous approaches may one day enable human genome targeting or editing during very early development."

The team's move into embryo editing coincides with a report by the U.S. National Academy of Sciences in February that was widely seen as providing a green light for lab research on germline modification.