Episode Transcript
Dr. Jones: If you knew that you had a gene that caused illness in your children, what are your choices? New research into editing genes in human embryos gives us some new choices and new dilemmas. This is Dr. Kirtly Jones from obstetrics and gynecology at 麻豆学生精品版 and this is The Scope.
Announcer: Covering all aspects of women's health, this is The Seven Domains of Women's Health with Dr. Kirtly Jones on The Scope.
Dr. Jones: Mutations in the genes we carry cause thousands of diseases. Some of the diseases are manageable and some are deadly. If we knew we had those genes and didn't want our biologic children to suffer those problems, what might be the choices?
Of course, you could toss the genetic dice and just hope that the next baby didn't have the disease. A lot of people do this. They can't afford other options, although the care of what might be a critically ill child has its own costs. Maybe they feel that the options of creating a child aren't in their hands. Maybe the disease they carry isn't life ending but is life limiting. They have to manage with this disease and they figure that the children will as well.
Okay, the next choice might be that you choose not to have biological children. Some people make that choice because the possible outcome of a child with a severe disease is too heartbreaking for them. They may adopt children or remain childless.
Another choice might be to use donor egg or donor sperm depending on whether the dad or the mom has the mutation and make a baby that way. Donor sperm are relatively inexpensive, donor eggs are not. Some people want their own biological children and may search for another path.
Genetic testing of early fetuses in the womb by collecting cells from around the fetus has allowed pregnant women and their partners to know if the fetus carries the abnormal gene. The couple can decide if they want to terminate the pregnancy. This was the only option until about 15 years ago for a couple to try to select a healthy pregnancy. Clearly, it can be heartbreaking for couples to terminate a wanted pregnancy but if they already had a child die from the disease, that option might be preferable.
About 15 years ago, pre-implantation genetic diagnosis became widely available in the U.S. Couples with a known genetic disease can have in vitro fertilization and their early zygotes, very early embryos, can be tested and only the healthy embryos placed in the uterus to hopefully implant and grow. The abnormal embryos can be discarded. In healthy fertile couples with genetic diseases, this technique can be very successful.
Now, this week a multinational group led by a team at Oregon Health Sciences University reported the first successful techniques in editing out a mutation in sperm from a man with genetic heart disease. They were careful and successful in creating what appears to be genetically normal embryos. Although the embryos weren't implanted and were discarded after testing, their new technique opens up new doors and asks some questions.
Wow, this reminds me of typing term papers 50 years ago on a typewriter. When you made a mistake on the page, you could use white out, but it looked bad. You had to start all over. Then came the electric typewriter which let you correct little errors but not big ones. Then magic happened, computers created word processing. You could cut and paste with a click. It would even tell you when you'd made a mistake. It completely transformed written document creation. That in mind, how did this Oregon team do it?
They used a gene editing technique kind of like word processing called CRISPR-Cas 9. A lot has been written about this genetic technique. You can watch it on YouTube, there are TED Talks. It was invented or perhaps we should say discovered by two women scientists, one from the U.S. and one from France.
The Oregon team put a little cool twist on this technique. They took the sperm from the man with a known mutation that causes heart failure, they added the sperm to donor eggs. After injecting the sperm into the egg, they added a molecule created in the lab to specifically cut out this abnormal gene from the sperm DNA. And the really cool part, the egg with the normal gene had natural gene repair mechanism that replaced the gene from the sperm that been cut out, with a copy of the normal gene from the egg. They even in the paper called it not "gene editing" but "gene repair."
The zygotes that were created with this technology were then tested and the majority of them were normal by genetic testing. Now, this was a very special kind of genetic problem. It came from the man and was carried in the sperm. The cutting and pasting happened very early after the sperm was added to the egg, waiting later after fertilization doesn't work as well. And other research teams using this technique in already fertilized eggs didn't find it worked as well. We don't know if this would work if the egg was carrying the mutation and that would be much harder to do as eggs are hard to get.
So why would a couple use this technique when it's perfected rather than other options we've already mentioned? Some people have philosophical or religious concerns about discarding embryos. This new technique isn't perfect and some abnormal embryos will still be created, so discarding embryos will still happen.
Should we do this just because we can? Maybe. Pre-implantation genetic diagnosis, the technique we can do now to replace only normal embryos is complicated but it works very well. You do need a bunch of embryos to make sure you have enough for some to be normal. Gene editing might allow for greater chance of getting normal embryos, if you don't make very many eggs.
Of course many people worry about a slippery slope of creating people with specific genes for certain traits, height, smarts, eye color. But the same kinds of arguments were put forth when any genetic testing of fetuses or embryos was first attempted. So this technology is not ready for general clinical use at this time. It's amazing that they could cut out the abnormal gene from the sperm and the eggs' DNA repair could create a new healthy gene. If the technology gets better, and it will, it'll be available somewhere in the world and some people will use it. So stay tuned and thanks for joining us on The Scope.
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