What the CRISPR Embryo Editing Study Really Taught Us

[Music] there's been a lot of hype in the last couple weeks about a study that used the gene editing technique CRISPR to modify human embryos the study was published on August 2nd in the journal Nature by American and Korean researchers and since then you might have heard concerns about designer babies in human genetic engineering run amok but the study's real findings were a little more modest a possible way to decrease the impact of one disease and the surprising discovery about how the human genome could protect itself from being changed CRISPR more formally known as CRISPR casts 9 is a relatively new genetic engineering technique it gives scientists more power and flexibility to edit DNA in living cells than they've ever had so lots of experiments are underway from cancer treatments and adults to modifying disease transmitting mosquitoes the system uses an enzyme called cast 9 which makes cuts in DNA a piece of RNA which cells normally use as a chemical messenger guides the calf 9 to a DNA sequence that matches up with the RNA sequence then cast 9 makes a cut through both DNA strands it's called a double-stranded break after that a couple of things could happen the cell might Jam those loose DNA ends together as quickly as it can even if it introduces mistakes but sometimes cells will fix the break by copying a DNA template instead it's going to happen for example of a cell is getting ready to divide and it's made a couple of copies of its DNA the cell can copy the copy to fix the original and everything's good with CRISPR researchers can provide a specific DNA sequence for the cells to use as a template during these repairs that way they can introduce any changes they want like adding a different version of the gene in this study the researchers were specifically looking at a gene called my BP c3 it's involved in a hypertrophic cardiomyopathy a disease that makes the heart muscle thicker and it can lead to sudden heart failure and death in young otherwise healthy athletes when they push their hearts too hard while exercising the disease can be managed with a variety of treatments but there's no real cure and if just one of a person's two copies of the gene as a mutation they're affected by the disease and can pass it on to their children these researchers wanted to use CRISPR task 9 to fix the gene in embryos to see if they could prevent it from being passed on from parent to child for their experiments they got sperm from a man with a mutant myb pc3 gene and eggs from several healthy women with no mutant genes they injected the sperm and the cast iron protein with its guide RNA directly into the eggs along with a single-stranded DNA template for a healthy version of the gene their goal was to get cast 9 to slice out any copies of the mutant gene and repair it with a healthy gene instead and the fertilized eggs went on to produce embryos with too healthy my bpc 3 genes in 42 out of 58 trials over 70% of the time in the control experiment without any CRISPR it was around 5050 that's what you'd expect because the man had one mutant copy and one normal copy so half of his sperm were carrying the new gene so the treatment worked a little more efficiently than no treatment plus the researchers were trying to avoid getting a mix of CRISPR treated and untreated cells in a single embryo they seemed to succeed in all but one fertilized egg because they injected the sperm at the same time as CRISPR when the researchers took a closer look at the DNA sequences they found something that they didn't expect see the scientists had marked their template in ways that wouldn't change the final gene product but would show up in sequencing but their markers weren't in almost all of the embryo cells with two healthy genes so they realized that when the fertilized egg cells fixed the double-stranded breaks made by cast nine almost all the cell's totally ignored the template that the researchers provided instead the cells use the healthy gene from the egg cell as a template to fix its disease counterpart from the sperm that's a mechanism for DNA repair that the researchers didn't see coming and it means a couple of big things first it suggests that there might be a way for our sperm and egg cells to resist changes in their DNA and a way that our other cells don't so researchers think this kind of makes sense since DNA in those cells is what lets us reproduce so it's really important to keep it intact second this newly discovered repair system could mean that embryos will reject a new DNA we try to give them so we could possibly use CRISPR to fix a problem like my BP c3 where one parents gene is bad and the other is fine but if genes from both parents are broken this mechanism might resist any attempts to introduce new DNA that's supposed to fix them other than this surprising finding the scope of this research is more modest than you might think from all the Bates sometimes a parent might know that they carry a dangerous gene like my BP c3 or the mutant BRCA gene that often leads to breast cancer so they might use in vitro fertilization with pre-implantation genetic diagnosis basically that's when a doctor helps people create fertilized eggs grows them into embryos and then screens them for disease genes and then implants only the healthy egg into someone's uterus the technique in this new study could help doctors grow healthy embryos more often and improve the efficiency of IVF having to create fewer embryos is easier on parents the Patrick of laws and different countries will make it difficult for this new technique to get off the ground though the study using human embryos for instance was only legal in the US because it was privately funded genetically engineering embryos to grow up into human beings is still way way off these were only grown in a culture for three days and we're still just a tiny ball of four to eight cells and a great deal of research is needed to refine the techniques developed in this study and make sure they're absolutely safe for any theoretical human use so whatever the headlines are saying we're really looking at a narrow but surprising study it showed us once again that there's still a lot we don't understand about how our bodies work and it's an incremental piece of research which is usually the case with science and if anything its results make designer babies less likely not more thanks for watching this episode of scishow news the other big science news right now is the solar eclipse that's happening next Monday we're very excited about here at scishow so if you want to learn more you can check out our video on scishow space and if you want more of this you can go to youtube.com/scishow and subscribe [Music] you [Music]

Channel: SciShow

Views: 297,812

Rating: 4.9433541 out of 5

Keywords: SciShow, science, Hank, Green, education, learn, designer babies, embryo, Genetically engineering, fertilized eggs, uterus, IVF, in vitro fertilization, MYBPC3, DNA, CRISPR, Cas9, gene, marker, sequencing, template, sperm, hypertrophic cardiomyopathy, gene editing technique, human genetic engineering, RNA

Id: BCO-U1glK14

Length: 6min 4sec (364 seconds)

Published: Fri Aug 11 2017

Reddit Comments

[u/OliverSparrow]

Sorry, can't be bothered with videos. However, one interesting thought is this. For a decade, pigs have been raised that have organs that lack the immune tags that provoke rejection if they are transplanted into humans. These haven't been used because pigs have a dangerous legacy in their genome.

Viruses like HIV use reverse transcriptase to write their nucleic sequence into the DNA of a species. Pigs have a number of these "genes" sitting like time bombs. These are viruses that do not at present effect human beings. Transplanted into a human, however, the fear is that the virus could be expressed, so jumping the species barrier. So "xenotransplants" - pig organs into humans - have been banned.

CRISPR-Cas9 can destroy such remnant DNA in the zygote (sperm, egg), rendering the pig so produced 'clean'. Provided we are able to identify every such sequence in the pig - which is now fully sequenced - then we can knock these out. Transplantation then moves into a new era.