Two thousand and sixteen was a big year for genetics, and there was no bigger story than everyone’s favorite gene-editing tool, CRISPR-Cas9. But that wasn’t the only story: A “three-parent baby” was born in Mexico, the minimum number of genes needed for bacterial life was determined, gene drives were tentatively approved for dealing with the Zika virus, and four species of giraffes were identified based on DNA alone. And there were many more.
Here's the rundown of our top stories.
The Many Tales of CRISPR-Cas9
For the last couple of years, there's been a lot of news about tweaking genes using the CRISPR-Cas9 system. In 2016, scientists began to use this cutting-edge gene-editing tool in earnest.
Last year was the first time that CRISPR-Cas9 was directly used to treat a disease in a patient. In late October, Dr. Lu You of Sichuan University in Chengdu, China used CRISPR-Cas9 to change the DNA in a patient’s immune cells so that these cells would attack the patient’s cancer. This approach is called immunotherapy--a big story all on its own.
What these researchers did was to remove immune cells from the patient and knock out their PD-1 gene, which can incorrectly determine that cancer cells are not a threat. Removing the gene should theoretically help the immune cells recognize and destroy cancer cells. The researchers grew the modified cells in the lab and then injected them back into the patient. While it is too soon to know if the treatment is effective, we do know that -- so far at least-- the patient hasn't experienced any negative effects.
The reason I included the quotation marks is that gene editing human embryos is still very much a work in progress. Only four of the 26 embryos were successfully edited. And the results were not identical even in these four; some had additional mutations in the targeted gene. These mixed results emphasize how much more work needs to be done before editing human embryos can become routine.
And of course, the CRISPR-Cas9 patent war between UC Berkeley and the Broad Institute of Harvard and MIT continued to rage on. Whoever wins stands to make a whole lot of money, which makes this a very nasty, ongoing battle unlikely to end soon.
CRISPR-Cas9 even became a player in the GMO field. The FDA ruled that a mushroom with a gene that had been modified with CRISPR-Cas9 didn’t need to jump through the usual regulatory hoops that a genetically modified organism has to.
Another big story last year, gene drives, owes its existence to CRISPR-Cas9:
Gene Drives, Mosquitoes and Zika
Last year, the Zika virus spread like wildfire across South and Central America, leaving over 1,000 babies with the birth defect microcephaly.
Scientists are working on a number of ways to prevent Zika infections. The most controversial is to wipe out the mosquito that carries the virus using gene drives.
Gene drives use CRISPR-Cas9 to quickly and easily spread a harmful gene through a population. In this case the idea would be to destroy the population of mosquitoes that carry the Zika virus.
Gene drives were mostly theoretical until CRISPR-Cas9 came along to make them a relatively simple thing to make. In fact, so simple that a group of undergraduate students nearly pulled it off at the end of 2016.
Child With Three Parents
In 2015, a big controversy swirled around whether to restart a genetic technique that allows some women who carry mitochondrial diseases to have children without passing them on to their kids. In 2016 a healthy baby boy was born in Mexico using this technique.
The technique is controversial for a couple of reasons. First, any girls born will pass their genetically engineered DNA down to their children. This has always been an ethics no-fly zone, as the feeling is that whatever genetic modification we make in a person should stay in that person. Because the woman in Mexico had a son, the issue was sidestepped.
The other controversy is that this boy has DNA from three people instead of the usual two.
The child has mitochondria, and thus mitochondrial DNA, from the donor, along with DNA from his mom and dad. (Mitochondria are the organelles that supply our cells with energy; they have a bit of DNA all their own.) Although this is referred to as having three parents, that might be a bit of an overstatement. After all, something like 1/300,000th of the child's DNA comes from the donor, with the rest coming from the mother and father. If the donor is a parent, she is a very minor one indeed.
The Edge of Life
With the exception of viruses, most life has evolved with a thousand or more genes.Humans have somewhere around 22,000 genes; the humble yeast that gives beer and wine its alcohol has around 6,000; and the bacterium with the fewest known number of genes has 901.
In 2016 a group of researchers was able to show that this last bacterium could get by with only 473 genes. This is the bare bones machinery needed to keep a bacterium going.
What is cool is that we would not have been able to predict that these were the 473 a bacterium would need. We don’t even know what 143 of them do... .
Genetics is bound to be a hot topic in 2017 as well. Stay tuned.
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