Podcast: The CRISPR children - episode 2
The 'CRISPR babies' are now children. This is a series about how they possibly are, how one might assess their health and, in this episode, how to not risk embryos that are genetically mosaic. Rudi Jaenisch of the Whitehead Institute for Biomedical Research explains.
In November 2018, the 'CRISPR babies' Lulu and Nana became famous and infamous. They are the first humans known to have had their genomes edited before their birth. There is also a third child whom I call Amy. I have always wondered how the "CRISPR babies are. They are now three-year-old children. Celebrities. Victims.
For my story The CRISPR Children in Nature Biotechnology, I asked around to find out how the children might be while also steering clear of invading their privacy or tarnishing their dignity. Here is episode 2 in a podcast series about these children. In February 2018, stem cell researcher Rudi Jaenisch got a visit from He Jiankui. In this podcast you can hear or read more about that visit and other aspects.
Here is episode 2 and a transcript is pasted below that.
Transcript of podcast
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The CRISPR children – episode 2
Yah, it’s totally unacceptable.
That’s Dr Rudi Jaenisch, a researcher at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts. What he is calling unacceptable is the experiment that led to gene-edited children who had been gene-edited before their birth.
You will hear more from Dr. Jaenisch in a moment. Just some context.
In the late summer of 2018, I received what we journalists sometimes call a heads up e-mail. Journalists get a lot of those.
This particular heads up was about the upcoming Second International Summit on Human Gene Editing that focused on the latest science related to human gene editing. It was going to be a surprising meeting, I heard. Okee I didn’t really know what to think. But I thought I would tune in.
Genetics, genomics, gene-editing, those are always important topics for me, among the many topics that I keep an eye on, journalistically
Then on November 25, 2018 as you may recall there was big news related to gene-editing.
A lab at Southern University of Science and Technology in Shenzhen China, the lab was run He Jiankui, had experimented with human embryos.
The team had edited the genomes of two human embryos. They fertilized eggs in the test-tube. The eggs were from a woman who had, it seems, agreed to the process. They fertilized the eggs with the sperm from her husband. Then they gene-edit4r the embryos, implanted the embryos into the uterus of the woman from whom they had removed the eggs. The pregnancy went to term.
Twins were born from this pregnancy, they born slightly prematurely. He Jiankui called the two of them Lulu and Nana in his talk at the summit. And didn’t disclose they had been born prematurely.
He had been invited to speak at the conference but he hadn’t planned to speak about the children. When the news broke he changed his talk around. He was eventually arrested and sent to jail along with two others in his lab.
There are three children whose genomes have been edited before their birth, three that we know of. The identical twins Lulu and Nana and a third child from a different mother and father whom I call Amy. At his talk in Hong Kong He Jiankui disclosed there was a third pregnancy. That was all he said.
It has always felt important to me to find out about these children, what had happened to them, how are they doing? I kept asking people about them. How might their health have been affected by this heritable gene-editing? I kept digging around. Lots of secrecy and rumor to dig through.
Three years later, I have published a story in Nature Biotechnology called The CRISPR children. And this rolling series of podcasts is to accompany this story to share more of what I have found out thus far.
There is so much secrecy about these children, Lulu, Nana and the third child was never given a name in public and but I have decided to call her Amy.
At locations in China known to a select few, the girls are growing up with their parents. They are around three years old. The girls are purportedly doing well, sources tell me. This is hard to verify and of course, I don’t want to infringe on their privacy or dignity. But I have always been concerned about what happened to these CRISPR babies who now CRISPR children.
A few people have seen photos of the children, others have spoken to their parents.
In all likelihood, the girls are genetically mosaic, which means, some but probably not all of their cells have edited genomes. So that’s unlike the typical situation of our bodies in which all cells having identical genomes.
At first Chinese authorities greeted this news about the gene-edited babies with enthusiasm. And quickly backtracked as it became clear how outraged the world was about this human experimentation.
It’s three years later and several reports have been issued, a number of books have been written and published about these events and many articles have appeared about these events, too. But I have been surprised and puzzled about how little has focused on the children themselves.
Of course their privacy needs to be maintained and their dignity has to remain untarnished. But what happened to them exactly, what experiments were done and what kinds of health ramifications might this have for their lives?
And since these have been heritable changes, if they choose to have children, how will the lives of their children and grandchildren be affected?
As I set out to find out more I was surprised how difficult it was to find out what had happened. It was a surprise to me how many scientists I queried got their backs up when I inquired with them. They refused to comment and didn’t want any part of an article that talked about these experiments. Odd.
But some people did agree to chat and I am grateful to them so this is a rolling series about some things I heard.
I have a number of sources whom I can’t name for various reasons. They told me much that has helped me report this story published in Nature Biotechnology. My editors there have been so very supportive of this project. And I sure am grateful for that.
Of course a lot is still not known and there’s so much secrecy and rumor.
Lulu and Nana’s parents have reportedly been threatened, there have been calls to bar the children from attending school with others. That’s so sad.
When I told Steven Salzberg, a genomics researcher at Johns Hopkins University about this, he called this “a crime against complete innocents.”
How are the children? Sources tell me they are ok. Which may or may not be true, I hope it is true.
The scientists responsible for the gene-editing were not acting alone, there was a lab, there were supporters, not just in China. He Jiankui kept many in the loop about what he was doing. There was a circle of trust as my journalistic colleague at Science Jon Cohen has phrased it in a fab article he did.
When He Jiankui, was doing these experiments and the work was underway, he actively began reaching out to labs as if he was seeking supporters for his plan.
He set out to visit with scientists. Rudolf Janisch of the Whitehead Institute got a visit from He Jiankui. Jaenisch works with stem cells is the first scientist to have generated transgenic mice.
So in February 2018 Rudi Jaenisch gets a visit from He Jiankui. Dr. Jaenisch thought it was going to be a discussion about science and experiments.
Rudi Jaenisch [6:32]
He came in February. The announcement was in November, he came in February, the experiment had been done, I think, he wanted to get approval from labs, Here, I think he want to other labs. Of course it was absolutely not acceptable. I didn’t realize the guy had already done it, I thought he was maybe thinking about this and that I could talk him out of this.
What he was thinking about, well what he had already done and was looking for approval after the fact for, so it seemed, was an experiment to edit the CCR-5 gene, the C-C chemokine receptor type 5 gene, which encodes a co-receptor for HIV. It’s a kind of molecular doorknob for HIV, the virus that causes AIDS. His idea was to generate people who were resistant to HIV by editing this gene.
For his experiments He Jiankui chose HIV discordant couples. The wife was HIV negative, the husband HIV-positive but being treated with anti-retroviral drugs.
Rudi Jaenisch [7:40]
He came to my office and want to suggest the experiment. And I said: This is nuts, there’s no justification to do this. I couldn’t take him seriously. He had already done it. It was very strange.
This experiment is totally unacceptable, obviously There was no medical need for these embryos—girls now--to have this done. Because if you want, the infection risk from the mother or father for AIDS is very low, you can prevent it. If you get AIDS you can treat it somatically, that’s been done now. There’s no need it in the germline.
The potential side effects by knocking out this receptor could be very serious because you might be more susceptible to other viruses like the Coronavirus. So there could be many disadvantages, if the experiment even worked.
So I think it was totally unacceptable. If he would have made ES cells, it would have been fine the we might have learned something like how efficient it is and all these things.
Instead of implanting the embryos, perhaps he might have used the embryos to generate embryonic stem cells, to do basic research only, to learn for example how efficient gene-editing is. To see for example how many cells remain unedited in spite of having been exposed to CRISPR reagents. He could have explored other scientific questions, such as where so-called off-targets can occur. But that was not the goal.
Rudi Jaenisch [9:13]
Viable embryos but he would convert them to ES cells, that’s allowed under the conditions. But he chose to implant them to make the first edited humans. That was outrageous. That is certainly, a no-no. There was no justification for this.
The lab’s plan had been to use HIV as a kind of test case to show how one can edit human embryos to prevent disease. He Jiankui and a friend and mentor John Zhang who owns a company called New Hope Fertility, had bee,n according to sources, planning a joint commercial venture, an in vitro fertilization clinic to offer to people who wanted to become parents to make gene-edited babies. This is not yet approved—anywhere. Germline gene-editing is not an approach that is condoned or accepted.
He Jiankui and John Zhang are not the first to come up with this idea of gene edited children as a service. Walter Isaacson in his biography of Nobel Laureate Jennifer Doudna recounts that in March 2014 Lauren Buchman approached Doudna’s colleague Dr. Sam Sternberg who is at Columbia University Irving Medical Center. The proposal was about a commercial venture called Happy Healthy Baby. The plan at Happy Healthy Baby was to use CRISPR to generate gene-edited babies. It appears that project was abandoned. But there might be others.
Back to the gene-edited babies we know about: Lulu, Nana and Amy.
Gene-editing technology is not ready for any kind of application in people to do what is called germline genome editing. One of the biggest scientific barriers is mosaicism. When gene-editing is performed with today’s technology, instead of just editing the genomes in the fertilized egg, cell division starts. The CRISPR reagents are still active. There are two cells or perhaps four or more. Some cells end up edited and some are un-edited.
What this leads to is a body with cells with non-identical genomes. This is called genetic mosaicism. It’s likely the genomes of the gene-edited girls, that would be Lulu and Nana and Amy are mosaic. If you wanted to assess if an embryo is mosaic, well, that’s scientifically practically impossible. Here’s Rudi Jaenisch:
Rudi Jaenisch [11:40]
Mosaicism is the principle problem. You cannot assess whether your manipulation worked ort not by biopsy, you can take one cell for pre-implantation diagnosis, to analyze it. But if it’s a mosaic, you don’t know whether you have a part of the edited embryo or the none edited part. It’s impossible. It’s basically impossible to verify whether your manipulation worked or not. It would not help.
So mosaicism is a big complication with germline gene editing. And the gene-edited children, three of them that we know of, are likely mosaic. It is quite hard to know if mosaicism has health consequences or not, I spoke with a few scientists about this. And there is more about this in other podcasts and in my article. Basically, there is no way to assess all cells in the body to see if mosaicism is causing a health issue.
It can and it might and it might not. Which is yet another reason why some scientists told me it’s definitely too early to apply CRISPR for these kinds of applications.
If embryo editing were approved, and this is just a thought experiment because it is not permissible, but stick with me here on a thought experiment.
If you wanted to do this experiment, you would need to assess if the gene-editing worked. The way to do that would be to make sure there are so to speak extra cells, cells one can test and that are identical to the ones in the embryo. You could make and assess clonal embryonic stem cells, called ES cells for short. But there are still difficulties. Here’s Rudi Jaenisch.
Rudi Jaenisch [13:45]
You get clonal ES cells and from this you can likely conclude what happened. The issue of course many of these embryos when edited at the one-cell stage will be mosaic in mouse and human also. It could be 50% or more. A given ES cell, which comes from one cell, then it might not be the edited one.
Rudi Jaenisch works on gene editing in mice. Mosaicism rates can be as high as 50% in mouse embryos.
Rudi Jaenisch [14:10]
We saw this some years ago in mice, 50. It’s a very high percentage. It’s very clear, we measured it.
Maybe more. It’s not clear. Maybe this is solvable at one point, but it is what it is.
Is this due to the guide RNA? Or CRISPR keeps cutting?
It’s only the integration, the cutting took place after the one-cell stage, maybe at the two cell stage. If it takes place at the two-cell stage, in one cell and not in the other, you have a mosaic.
It’s a mix of cells, half of the cells will be unedited, the others edited.
When you biopsy later, you never know which one you got. You can’t really diagnose an embryo being corrected edited or edited at all by biopsy. You might get the mosaic and then you don’t know what you got.
Mosaicism is a problem, perhaps an insurmountable one. If heritable gene editing is to ever be considered and only if it’s approved and there’s consensus about it in society, if heritable gene editing is to be considered, one approach scientists say is to not edit embryos. But to edit the genomes in germ cells, egg or sperm. For example, one idea is to edit cells in animals or in people that give rise sperm and those would be spermatogonial stem cells.
For example Harvard Medical School researcher George Church has presented this as a way to perform heritable gene-editing, if this is approved and deemed ethically acceptable.
One would edit these stem cells that give rise to sperm. Or one might use induced pluripotent stems cells that are differentiated into eggs. Rudi Jaenisch agrees with this idea from George Church.
Rudi Jaenisch [16:10]
He’s totally right, I totally agree with this. Spermatogonial stem cells or oocytes, for mice at least. From iPS cells you can make oocytes which can be fertilized. Both of these cell types you can clone.
Spermatogonial stem cells, you can clone. So you can edit a cell, make several clones, take one clone, you can do analysis you want. It’s clonal. If you are satisfied, everything is fine, you can can inject the other clone into the testis for example or fertilize with this. This would indeed be a way to verify what you did. You have two sibling clones. One you analyze everything, when you’re satisfied, the other will be the same, they are sibling clones. You can do this not only with sperm also with oocytes, at least with mice. In humans it has not been done yet but it will probably work.
You can take iPS cells, differentiate them into oocytes which can be fertilized. The you can do everything on the iPS level. Be sure you have the right iPS cell, edited the right way. From those clone you make oocytes, which could be fertilized.
So with induced pluripotent stem cells, you can differentiate them into oocytes or egg cells which you can fertilize. Rudi Jaenisch is talking about mice here but in theory one can do this with human eggs.
When performing this work with spermatogonial stem cells, you do not get mature sperm, they are immature and cannot fertilize an egg on their own, but you can inject them into an egg in a process called ICSI. ICSI stands for intracytoplasmic sperm injection. It’s done in in vitro fertilization and was also used to fertilize the eggs that ultimately led to Lulu, Nana and Amy.
Here’s Rudi Jaenisch about using spermatogonial stem cells
Rudi Jaenisch [18:12]
If you make sperm you can’t make mature sperm but you can make immature sperm, they don’t fertilize by themselves. You can inject them. ICSI, it’s standard in the clinic. ICSI means sperm injection into an unfertilized egg. It’s been shown in mice, if you put this into an egg, then you get mice. It’s a proof of principle.
When experimenting in mice to explore gene-editing as many labs do, including the Jaenisch lab, one always has to keep in mind that mice and human cells are different and gene-editing can work differently in mice than in humans.
Rudi Jaenisch [18:50]
I think there could be clearly differences in human and mice in these development always something to consider. Could be repair enzymes, metabolism is different in human and mice, also repair processes.
One day and that day is not now, one might consider performing gene editing in human embryos. And one might choose to edit germ cells.
Rudi Jaenisch [19:20]
If you do it with spermatogonial stem cells, Church, I agree with him, then I think the scientific issues might go away. So then it becomes an ethical issue, do you want to do this under what circumstances?
If you do it with embryos, in addition to scientific issues you have ethical issues, which we talked about, ,mosaicism, not being able to assess what you did. Embryos have two major issues, scientific as well as ethical. Spermatogonial stem cells maybe only ethical. It’s a key one of course. Do you want to do this, under which circumstances, for what? These are important questions.
Resolving if and when to use heritable gene editing still needs discussion. When it comes to preventing disease, heritable gene editing might not be the only option. Here’s Rudi Jaenisch
Rudi Jaenisch [20:04]
Most of the cases you could do this by preimplantation diagnosis. Most parents will have a dominant disease, 50% normal embryos, you can select them. You don’t need this. So now the big question is under which circumstances would this be the only option?
Huntington’s is a dominant disease. If you have homozygous for Huntington’s, which is very rare. There’s no way such a person could have a healthy related kid, no way. That might be the only time when you might consider that.
Such scenarios were discussed by the National Academy of Sciences panel that included Jaenisch. The panel convened and published a report and that was before He Jiankui did his experiments.
To avoid heritable conditions, such as those that lead to an infant’s early death and for which no therapy exists, parents can choose in vitro fertilization and pre-implantation diagnosis. A cell from the embryo is checked to see if the embryo has the inherited disorder.
Rudi Jaenisch [21:14]
You can always do preimplantation diagnosis. It’s very rare that you can’t. Both parents are homozygous for a recessive disease? There’s no way they can get a healthy child.
But when one is homozygous, the other is not, you still get 50% of embryos, actually more, will be normal, maybe carriers, but they will be normal. There are very few instances when you would need that. And then one still has to consider should one do this or not. These are very complicated questions.
Indeed these are very complicated questions. And it will take discussion to resolve these. And open discussion is better than secrecy and rumor. Many scientists did not wish to talk about these questions with me.
I am grateful to Rudi Jaenisch for the fact that he did take the time to chat about these questions. And just adding this here, The Whitehead Institute or MIT did not pay to be in this podcast. This is independent journalism produced by me in my living room.
In the notes to this show are links to the story I did for Nature Biotechnology and some of the resources I have drawn on in reporting this story. I’m Vivien Marx, thanks for listening.
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