CRISPR-Cas9 is the cutting-edge genomic technology that essentially lets you target exact sequences in DNA and then cut into them like a knife and insert or remove a gene. You may remember it from that Chinese scientist who successfully (but controversially) implanted gene-edited embryos into a woman who then gave birth to live lab babies. More often, it's used to create things like malaria-resistant mosquitoes or mushrooms that don't brown as fast.

But it does have a lot of practical medical potential, too. It's already been used to remove HIV from a patient's genome. And now, after CRISPRing out a blindness-causing gene from mice, scientists have now successfully scaled-up this procedure to work in a live human body. From NPR:

In this new experiment, doctors at the Casey Eye Institute in Portland, Ore., injected (into the eye of a patient who is nearly blind from a condition called Leber congenital amaurosis) microscopic droplets carrying a harmless virus that had been engineered to deliver the instructions to manufacture the CRISPR gene-editing machinery.

[…]

The goal is that once the virus carrying the CRISPR instructions has been infused into the eye, the gene-editing tool will slice out the genetic defect that caused the blindness. That would, the researchers hope, restore production of a crucial protein and prevent the death of cells in the retina, as well as revive other cells — enabling patients to regain at least some vision.

[…]

The procedure, which takes about an hour to perform, involves making tiny incisions that enable access to the back of the eye.

Russian scientist Denis Rebrikov claims that he's begun a gene-editing process to eventually enable couples who both carry a specific genetic mutation that causes deafness to birth children who can hear. Rebrikov formerly announced his effort to use the CRISPR tool for gene editing to create babies resistant to HIV. From Nature:

In his e-mail to Nature, Rebrikov makes clear that he does not plan to create (a gene-edited) baby yet — and that his previously reported plan to apply this month for permission to implant gene-edited embryos in women has been pushed back.

Instead, he says that he will soon publish the results of his egg experiments, which also involved testing CRISPR’s ability to repair the gene linked to deafness, called GJB2, in bodily cells taken from people with this mutation. People with two mutated copies of GJB2 cannot hear well without interventions, such as hearing aids or cochlear implants. Rebrikov says these results will lay the groundwork for the clinical work.

Rebrikov adds that he has permission from a local review board to do his research, but that this does not allow transfer of gene-edited eggs into the womb and subsequent pregnancy...

Some scientists and ethicists also call into question the benefits of this procedure because hearing loss is not a fatal condition. “The project is recklessly opportunistic, clearly unethical and damages the credibility of a technology that is intended to help, not harm,” says Jennifer Doudna, a pioneer of the CRISPR gene-editing tool and a biologist at the University of California, Berkeley.

Scientists believe that the "CRISPR twins," who had their genes edited last year before birth, will now have an easier time learning and memorizing. Apparently, the gene alteration, which was meant to make the girls immune to HIV, also altered their brains. Read the rest