In the paper, Fan, who works at Guangzhou Medical University in China, and his team say that they collected a total of 213 fertilized human eggs between April and September 2014. The fertilized eggs, donated by 87 patients, were unsuitable for implantation as part of in vitro fertility therapy, because they contained an extra set of chromosomes.
Fan’s team used CRISPR–Cas9 genome editing to introduce into some of the embryos a mutation that cripples an immune-cell gene called CCR5. Some humans naturally carry this mutation (known as CCR5Δ32) and they are resistant to HIV, because the mutation alters the CCR5 protein in a way that prevents the virus from entering the T cells it tries to infect.
Genetic analysis showed that 4 of 26 human embryos targeted were successfully modified. But not all the embryos’ chromosomes harboured the CCR5Δ32 mutation — some contained unmodified CCR5, whereas others had acquired different mutations.
George Daley, a stem-cell biologist at Children’s Hospital Boston in Massachusetts, says that the paper’s main advance is the use of CRISPR to introduce a precise genetic modification successfully. “This paper doesn’t look like it offers much more than anecdotal evidence that it works in human embryos, which we already knew,” he says. “It’s certainly a long way from realizing the intended potential” — a human embryo with all its copies of CCR5 inactivated.
“It just emphasizes that there are still a lot of technical difficulties to doing precision editing in human embryo cells,” says Xiao-Jiang Li, a neuroscientist at Emory University in Atlanta, Georgia. He thinks that researchers should work out these kinks in non-human primates, for example, before continuing to modify the genomes of human embryos using techniques such as CRISPR.
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Fan’s team used CRISPR–Cas9 genome editing to introduce into some of the embryos a mutation that cripples an immune-cell gene called CCR5. Some humans naturally carry this mutation (known as CCR5Δ32) and they are resistant to HIV, because the mutation alters the CCR5 protein in a way that prevents the virus from entering the T cells it tries to infect.
Genetic analysis showed that 4 of 26 human embryos targeted were successfully modified. But not all the embryos’ chromosomes harboured the CCR5Δ32 mutation — some contained unmodified CCR5, whereas others had acquired different mutations.
George Daley, a stem-cell biologist at Children’s Hospital Boston in Massachusetts, says that the paper’s main advance is the use of CRISPR to introduce a precise genetic modification successfully. “This paper doesn’t look like it offers much more than anecdotal evidence that it works in human embryos, which we already knew,” he says. “It’s certainly a long way from realizing the intended potential” — a human embryo with all its copies of CCR5 inactivated.
“It just emphasizes that there are still a lot of technical difficulties to doing precision editing in human embryo cells,” says Xiao-Jiang Li, a neuroscientist at Emory University in Atlanta, Georgia. He thinks that researchers should work out these kinks in non-human primates, for example, before continuing to modify the genomes of human embryos using techniques such as CRISPR.
- More Here
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