When scientists discover a new way to prevent disease or overcome infertility, they usually get applauded. But throw genetic engineering into the mix and it gets dicey fast. Genetic engineering in reproductive medicine is particularly scary because we’re talking about...
3-Person IVF: A Resource Page
3-person IVF encompasses a range of techniques that would create an embryo with genetic material from three different people and result in germline modification (changes to early human cells that would be passed on to future generations). These techniques have been referred to with several terms, including "mitochondria replacement," "mitochondrial manipulation," "mitochondrial transfer," "oocyte modification," "3-person IVF, " "3-person embryos," "3-parent babies," and "nuclear genome transfer" (the most technically accurate). As an accessible shorthand on this resource page, we employ the term "3-person IVF" for these techniques.
3-person IVF has the stated goal of allowing a small number of women with a rare kind of severe mitochondrial disease to have a healthy and mostly genetically related child. The techniques work by transferring the nucleus of an affected woman's egg (or the nucleus of a fertilized embryo) into another woman’s enucleated egg or embryo (from which the nucleus has been removed but the mitochondria remain). Inheriting nuclear DNA from the intended mother and father and mitochondrial DNA from the egg provider, the child would thus be genetically related to three people. It is for this reason that the media often refers to "three-parent babies" or "three-parent in vitro fertilization."
While mitochondrial disease is the most widely stated aim of 3-person IVF at the moment, we know that some scientists are already seeking approval for its use in non-disease related fertility treatments. This could open the door to wide-scale embryo genetic engineering for reproduction, absent clear medical necessity.
Critical questions about the safety and efficacy of these techniques have not yet been answered, and they raise profoundly important social and ethical questions. A strong and long-standing international agreement against human germline modification currently exists, along with explicit prohibitions in dozens of countries, due to profound ethical and human rights concerns regarding human biological experimentation.
In February 2015, the United Kingdom became the only country to give regulatory approval for germline modification, carving out an exception to its wider prohibition on human germline modification to allow for 3-person IVF (see below).
This decision crossed the line established by international consensus for the first time. In the absence of such regulatory controls, advances in gene editing could open the door to more and different kinds of germline modifications in the future (see here).
The last quarter of 2016 saw an explosion of activity in the area of 3-person IVF:
On September 27, 2016, New Scientist reported that a baby created using a 3-person IVF technique had been born five months previously to a Jordanian couple at risk for mitochondrial disease. The procedure was conducted by Dr. John Zhang, a NYC-based fertility doctor, who did the work in Mexico in order to evade the US regulatory process. A number of serious concerns have been raised in the scientific community, including the study’s dangerous flouting of regulations, making this an unethical living human experiment, the shoddy nature of the work itself, its promotion of medical tourism, and the unknown long-term effects of the technique. Wider media coverage of this event has been predominantly celebratory, downplaying the serious risks involved for the boy and future generations. For more, see here.
On October 10, 2016, New Scientist reported claims from Valery Zukin, a fertility doctor in Kiev, Ukraine, that he had used 3-person IVF as a treatment for general infertility, not to lower the risk of mitochondrial disease, for two women currently pregnant in their third trimesters and due in early 2017. The media was surprisingly quiet immediately after, although the BBC did publish a somewhat critical piece entitled “3 person baby ‘race’ dangerous.”
On October 19, Nature News broke news of a live birth reported in China using some kind of mitochondrial transfer technique. The research report is said to be under review at another journal.
On October 24, 2016, Reproductive BioMedicine Online published the first follow-up study of children born in the late 1990s and early 2000s using a precursor to 3-person in vitro fertilization (IVF) known as cytoplasmic or ooplasmic transfer (see “Weren’t children already born years ago following cytoplasmic transfer?” below). As the authors state, although the resulting children appear healthy, the study is inconclusive due to a number of serious limitations. The media misinterpreted the study as evidence that not only this specific technique but all forms of 3-person IVF are safe.
On November 1, Reproductive BioMedicine Online published “Setting the Record Straight,” an editorial response to the “shoddy scientific journalism” surrounding the Oct 24 article. Railing against the above misinterpretation, the editor argued that “the technique of cytoplasmic transfer in the late 1990s is so different from those of pronuclear or spindle transfer as to make the apparent normality of the offspring born through the former technique of little relevance in the context of (the latter).” In other words, the study doesn’t prove anything about the current or future safety of experimental 3-person IVF techniques.
On November 10, a study co-authored by Shoukhrat Mitalipov was published in Stem Cell, proposing the introduction of 3-person IVF technology as a fertility treatment. Characterized by one of the co-authors as “just one additional advance over IVF,” the new study promises a two-for-one deal for aging women to “increase the yield … available for transfer from a single stimulation cycle” using polar body nuclear transfer.
On November 30, another study co-authored by Mitalipov was published in Nature that suggests that reversion is a serious problem related to “mismatches” between the mitochondrial DNA of the intending mother and that of the egg-provider. The authors propose an as-yet-untested system of mtDNA replication-rate matching that would allow the egg provider’s mitochondria to remain dominant in the developing embryo. Scientific American recognized the hurdle this poses for clinical uses of 3-person IVF technology, describing it as “a biological curve ball” that shows that mitochondrial diseases “can come back to sicken a child, even when 99 percent of the mother’s own mitochondria are eliminated,” although most media reports managed to spin this setback as progress.
On December 15, the UK’s Human Fertilisation and Embryology Authority (HFEA) approved the clinical use of 3-person IVF technologies for the purpose of avoiding serious mitochondrial disease. This decision was based on a review it released on November 30 that examined the safety and efficacy of 3-person IVF techniques for this purpose. The review recommended “cautious use” of these techniques for “carefully selected patients” in cases “where there are no acceptable alternatives.” Clinical applications of these techniques are expected to begin in the UK in 2017.
To quickly get up-to-date on 3-person IVF, please see:
- Comment on UK Decision to Move Ahead with “3-Person IVF”, CGS Press Statement, December 15, 2016
- Comment on "3-person IVF" procedures for infertility reportedly conducted in Ukraine, CGS Press Statement, October 10, 2016
- 3-Person IVF Breaking News: Where Are the Advocates for the Public Interest?, CGS Blog, October 7, 2016
- Comment on use of mitochondrial manipulation techniques by US scientists in Mexico, CGS Press Statement, September 27, 2016
- Top 10 myths about 3-person IVF, Paul Knoepfler, Knoepfler Lab Stem Cell Blog, February 10, 2015
- Britain is on the brink of a perilous vote for 'three-person in vitro fertilization', Marcy Darnovsky and Jessica Cussins, Los Angeles Times, February 8, 2015
- Genetically Modified Babies, Marcy Darnovsky, The New York Times, February 23, 2014
United States. On February 25 and 26, 2014, the US Food and Drug Administration held a public meeting of its Cellular, Tissue and Gene Therapies (CTGT) Advisory Committee that included discussion of "mitochondrial manipulation techniques." In his summary of the committee’s discussions, chair Evan Snyder said that there is not enough data from animal or in vitro experiments to safely move on to humans. Webcasts of both days of the meeting are available here. For an overview of what happened, see here.
On January 27, 2015, a newly appointed committee of the Institute of Medicine (IOM, now called the National Academy of Medicine) held the first in a series of meetings to fulfill the FDA’s request to consider the ethical and social policy issues raised by “genetic modification of eggs and zygotes to prevent transmission of mitochondrial disease.” The meeting was the first public event in an FDA-sponsored study intended to take place over the next 14 months.
In February 2016, the FDA-sponsored study was published by the National Academies Press as Mitochondrial Replacement Techniques: Ethical, Social, and Policy Considerations. Based on a distinction it drew between the heritable genetic modification represented by “mitochondrial replacement techniques” (MRT) and the heritable genetic modification of nuclear DNA, the committee concluded that it would be ethically permissible to conduct clinical investigations of MRT as long as they were subject to the strict conditions and principles outlined in the report.
Significantly, the committee recognized that neither of the potential benefits to be gained through the procedure would directly benefit the child itself: 1) the benefit to the prospective parents of having a child genetically related to the prospective mother via nuclear DNA; and 2) the population level benefit of having fewer children born with serious mtDNA disease. It also acknowledged that MRT “would not treat an existing person for a disease, illness, or condition, so it does not address a medical need.”
United Kingdom. The UK Human Fertilisation and Embryology Authority (HFEA) released a published report of their third update on safety and efficacy of these techniques on June 3, 2014. See CGS's press statement here.
On February 24, 2015, the House of Lords approved regulations (following approval by the UK House of Commons earlier in the month) that carve out an exception to the prohibition on human inheritable genetic modification in the UK for the use of pronuclear transfer (PNT) and maternal spindle transfer (MST) to avoid mitochondrial disease. This allows fertility clinics to apply to the Human Fertilisation and Embryology Authority (HFEA) for a license to use 3-person IVF techniques without human clinical trials, and with no required follow-up of any resulting children. The regulations went into effect October 29, 2015. Although the regulations make it lawful for clinics to apply for use of these techniques, the HFEA determined it must first be satisfied that they are both safe and efficacious.
On November 30, 2016, the HFEA released a review that determined that 3-person IVF techniques are, in its opinion, currently both safe and effective. The review recommended “cautious use” of these techniques for “carefully selected patients” in cases “where there are no acceptable alternatives.” It suggested that reversion, the phenomenon whereby carried-over “faulty” mtDNA multiply faster than donor mtDNA and eventually take over the donor egg, does not pose a serious risk despite evidence to the contrary. It also rejected a U.S. National Academy of Medicine report that recommends limiting clinical research to the transfer of male embryos so as to avoid inheritable genetic modification.
On December 15, 2016, the HFEA gave the green light for clinical use of 3-person IVF technologies for the purpose of avoiding serious mitochondrial disease. No baby has yet been born in the UK as a result of 3-person IVF, but births are expected in 2017.
- Overviews and Background
- International Law and Human Rights Documents
- Critical Correspondence (articles, op-eds, letters)
- Biopolitical Times Blog Posts (2012-present)
- Why is this being explored?
- What are the different techniques?
- Where is the research taking place?
- What concerns does 3-person IVF raise?
- How many people would use this technology?
- Can people use PGD to have a genetically related healthy child?
- Is "mitochondrial donation" similar to other kinds of donation?
- How has the media covered the issue?
- Weren't children already born years ago following cytoplasmic transfer (ooplasmic transfer), a similar germline modification technique? What happened with that?
- How can I get involved?
Mitochondria are tiny organelles found in the cytoplasm of all living cells possessing cell membranes, including all animal and plant cells. They play important roles in helping regulate cellular energy use and cell growth, particularly with regards to metabolism, obesity, and lifespan. Mitochondria are of special interest because they possess their own genome, independent of the main cellular genome housed in the cell nucleus.
|Mitochondria are responsible for producing more than 90% of the energy needed in our bodies; failures of this system through inherited or spontaneous mutations of mitochondrial DNA (mtDNA) or nuclear DNA (nDNA) can cause damage to the brain, liver, heart, skeletal muscles, kidney, and the endocrine and respiratory systems. Because mitochondria play such a complex role in our bodies, performing different functions in different tissues, there are hundreds of different mitochondrial diseases. Mitochondrial disease often affects children, but is also common in adults due to deteriorating mitochondrial function with age.|
So-called "mitochondria replacement" is a new approach, the goal of which is to allow a woman who has mutations in her mtDNA to lessen the risk of passing on inherited mitochondrial disease to her child. The techniques being developed are variations on combining the nuclear DNA from an egg of an affected woman with the mtDNA of an unaffected woman's egg. A resulting child would possess genes from three adults, and this altered genome would be passed on to succeeding generations.
Mitochondrial disease is known to affect about 1 in 5,000-10,000 people, but the techniques being investigated would be inapplicable to approximately 85% of cases, because they are caused by problems in nuclear rather than mitochondrial DNA. Nor would these techniques prevent mitochondrial disease that arises due to spontaneous mutations or deterioration with age.
(See diagram here)
Pronuclear transfer begins with an embryo created via in vitro fertilization, using the intending parents’ sperm and eggs. Simultaneously, a second embryo is created using a donor egg with healthy mitochondria and the intending father’s (or donor) sperm. When the embryos are one day old, still at the single-cell stage, the pronuclei are removed from the first embryo. Some of the intending mother’s mutated mitochondria are inevitably carried over from the enucleated embryo, which is discarded. Meanwhile, the pronuclei of the second embryo are removed and discarded. The intending parents’ pronuclei are then placed into the second embryo, which has maintained the healthy mitochondria from the donor’s egg. This constructed embryo can continue to develop and then be transferred into the intending mother.
Researchers at Newcastle University have done extensive work attempting to develop the technique and to advocate for the UK to carve out an exception for PNT in the wider ban on human germline modification. This exception was put into effect in 2015. For more information, see the section “Where is the research taking place?” below.
(See diagram here)
In this technique, nuclear DNA is removed from the intending mother’s egg; the rest of the egg is discarded, including the unhealthy mtDNA. The nuclear DNA of an egg from a woman with healthy mitochondria is removed at the same time, leaving her healthy mitochondria in the cytoplasm. The intending mother’s nuclear DNA is placed into the enucleated donor egg, which can then be fertilized with sperm from the intending father. The resulting embryo can then be transferred into the intending mother.
Researchers at Oregon Health and Science University have created rhesus macaque monkeys using maternal spindle transfer, but their published report (2012) of this study failed to consider several key aspects of safety. The monkeys were followed for only three years, not long enough to generate useful data since mitochondrial disease often develops late in life. And because the genetic alterations would be passed to subsequent generations, multi-generational safety data are needed.
In addition, a worrying difference has been noted between the study of MST on the rhesus macaques and the trials on human zygotes: More than half of the human MST zygotes had abnormalities that were not observed in the monkeys. Some experts believe that human oocytes are more sensitive to spindle manipulations than monkey oocytes, a significant variation that requires further study before MST is used in humans.
MST and PNT can also involve other kinds of errors. Genetic material can be lost during transfer; small amounts of mtDNA from the unhealthy egg can be transferred and eventually replicate to take over the cell; a mismatch between foreign mtDNA and nuclear DNA can occur; and the segregation of mutated mtDNA to specific tissues may lead to a significant accumulation of the mutant load. Negative effects caused by any of these would not be reversible.
Nuclear Genome Transfer (NGT)
(See full report [pdf])
Nuclear genome transfer is essentially the same as MST. Scientists at Columbia University in New York, working with human eggs, developed a technique that avoided premature oocyte activation and thus increased success rates. (They did not fertilize the eggs, but did activate them via parthenogenesis.) NGT research is still in preliminary stages, and the researchers working on it recognize the need for studies on a larger number of samples, and on animal models. They also realize the need to publicly discuss patient needs, ethical considerations, and appropriate guidelines for the use of this procedure in assisted reproduction, if it were to be approved for human clinical trial.
(See full report here)
Also known as polar body transfer (PBT), polar body nuclear transfer is a new and more experimental technique than the others. Instead of transferring the pro-nucleus or maternal spindle, it transfers the genetic material from polar bodies, small cells produced during oogenesis that contain nuclear DNA but that typically don't develop into eggs that can be fertilized. It is hypothesized that this would reduce carryover of mutant mitochondria since polar bodies contain few mitochondria, but seem to have the same genomic information as the oocyte. Normally, polar bodies can't survive since they don't have mitochondria, but the theory is that in this case they would get it from the donor egg.
There has been little to no public discussion of this third technique. It was not considered in the FDA's meeting, nor was it considered throughout the process in the UK until the Government asked the HFEA to assess the technique's safety and efficacy in July 2014. The HFEA complied and released an addendum to its third safety review on 14 October 2014, acknowledging that "compared with both PNT and MST, it is clear that PBT is at an earlier stage of development, with little or no human data publicly available for the methods."
At this time, we have been unable to verify if the regulations that have been passed in the UK will enable eventual use of this more experimental technique or if new regulations would be needed, pending more data.
In November 2016, a study in Stem Cell co-authored by Mitalipov proposed the use of PBNT as a fertility treatment.
|Researchers at Newcastle University, particularly Douglass Turnbull and Mary Herbert, have been researching pronuclear transfer (PNT) for many years, developing related cloning techniques to create embryonic stem cells. For years, Newcastle researchers petitioned the UK government and the HFEA to carve out an exception for PNT, which went into effect in 2015, allowing PNT in fertility clinics without further work in nonhuman primates or clinical trials.|
Despite their law-changing advocacy, the researchers acknowledged early on that the technique was not ready for clinical trial or use (see statements in 2008, 2010, 2011, 2012, and later in 2013, 2016). They opened a center in September 2012 to undertake the follow-up work that was requested by the HFEA. Studies have focused on pronuclear transfer in mice, and more recently human embryos. In 2016, the center published research reporting problems with the PNT techniques which “were not well tolerated” by human embryos. They stated that “PNT has the potential to reduce the risk of mtDNA disease, but it may not guarantee prevention.” This is because, as The Guardian described, “the faulty DNA came back”: the 2016 study showed levels of at-risk maternal DNA remained in PNT embryos (between 2-5%), and grew in percentage relative to the donor mtDNA over time under lab conditions.The researchers proposed developing a new technique they dubbed early PNT or “ePNT.”
Oregon Health and Science University
Researchers at Oregon Health and Science University (OHSU), particularly Shoukhrat Mitalipov, have focused on maternal spindle transfer (MST). They have created "three-parent blastocysts" and used them to generate embryonic stem cells, as a demonstration that the blastocysts could create a viable embryo and child. In 2009, they used the same process in rhesus macaques, producing four live offspring, which appear to be healthy and developing normally. In February 2012, Shoukhrat Mitalipov filed a patent for MST as a technique for providing prenatal treatment for mitochondrial disease in humans.
The OHSU researchers, who have been privately funded to date, are explicit about the fact that if this technique were used in humans, it would irreversibly alter the human germline. The FDA has in effect banned this kind of modification since 2001, when it ordered an end to unauthorized efforts using earlier mitochondria replacement techniques. The have asked the FDA to lift its restrictions, and to break from its long-standing position against approving research that results in modification of the human germline. In particular, it was reported in February 2015 that Mitalipov requested permission from the FDA to conduct trials to treat age-related infertility with 3-person IVF techniques in the United States.
In January 2015, Mitalipov and his for-profit company MitoGenome Therapeutics teamed up with Chinese stem cell banking company Boyalife and the Korean company H-Bion, led by disgraced cloning researcher turned dog-clone entrepreneur Hwang Woo-suk, to start a lab in China, hoping that “things might go faster” there. In a Nature News article, Mitalipov described the collaboration as a way to move his 3-person IVF research forward, stating, “Fertility and mitochondrial disease are a big clinical opportunity.”
On November 10, 2016, Mitalipov co-authored a study in Stem Cell that proposed the introduction of 3-person IVF technology as a fertility treatment. Characterized by one of the co-authors as “just one additional advance over IVF,” the new study promises a two-for-one deal for aging women to “increase the yield … available for transfer from a single stimulation cycle” using polar body nuclear transfer.
On November 30, 2016, Mitalipov co-authored a study in Nature that suggested that reversion is a serious problem related to “mismatches” between the mitochondrial DNA of the intending mother and that of the egg-provider. The authors proposed an as-yet-untested system of mtDNA replication-rate matching that would allow the egg provider’s mitochondria to remain dominant in the developing embryo. Scientific American recognized the hurdle this poses for clinical uses of 3-person IVF technology, describing it as “a biological curve ball” that shows that mitochondrial diseases “can come back to sicken a child, even when 99 percent of the mother’s own mitochondria are eliminated.”
Columbia University, New York
In December 2012, Columbia University scientists, in conjunction with the New York Stem Cell Foundation, published a paper in Nature describing their results with what they refer to as “nuclear genome transfer.” Their technique represents a variation of MST, which they present as an improvement over PNT. Their paper, unlike the one by OHSU researchers, does not acknowledge that mitochondria replacement would constitute germline modification.
In August 2016, researchers from Sun-Yat Sen University of Medical Science in Guangzhou, China, along with colleagues from the New Hope Fertility Center in New York City, published the results of research conducted more than a decade previously in China. The publication, in Reproductive Biomedicine Online, came 13 years after they first reported their work at the 2003 meeting of the American Society for Reproductive Medicine. Dr. John Zhang, the first author of the study, told the press he had “delayed publishing the paper because of the ‘heat’ around the issue at the time.”
The study reported a case of 3-person IVF using pronuclear transfer (PNT) in which all fetuses in a triplet pregnancy were lost. A critical commentary accompanying the article, written by Dr. Jacques Cohen, director of Tyho-Galileo Research Laboratories and Dr. Henry Malter, director of Laboratories at Fertility Center of the Carolinas, raised a number of questions about the study concerning its lack of important data sets, lack of information about its review and ethics approval process, and the ethics of the technique itself in light of the availability of preimplantation genetic diagnosis (PGD) for treating mitochondrial disease.
See Key Questions about the social and ethical implications of 3-Person IVF techniques
The critical question of whether 3-person IVF is safe has not yet been resolved. Some remaining concerns include:
- Epigenetic harm caused by nuclear transfer (See here and here)
- Mito-nuclear mismatch (See Reinhardt, et al.; Dunham-Snary and Ballinger; and Muir, Diot, and Poulton)
- Impact of mitochondria on traits i.e. not just metabolic function (See Dowling, also New Scientist here and here)
- Reversion, the phenomenon whereby even tiny amounts of carryover mutated mtDNA replicate faster than donor mtDNA, eventually taking over the cell (See Burgstaller et al., also Nature here and here)
For an in-depth list of the reports in which scientists have identified risks, see here.
These issues could cause immediate problems for any child born from these techniques, but could also cause problems later in life. Any problems that arise would additionally be passed on to future generations.
3-person IVF would result in inheritable genetic modification. Altering the human germline is considered to be the most objectionable of genetic technologies and has constituted a bright line not to be crossed. Many bioethicists, scholars, and advocates from around the world have argued that "mitochondria replacement" does not justify crossing this line.
The 1966 United Nations International Covenant on Civil and Political Rights, which the US has signed and ratified (with some reservations), states in Article 7 that, "No one shall be subjected without his free consent to medical or scientific experimentation."
The 2004 European Union treaty establishing the European Constitution states in Article 63:
1. Everyone has the right to respect for his or her physical and mental integrity.
2. In the fields of medicine and biology, the following must be respected in particular:
(a) the free and informed consent of the person concerned, according to the procedures laid down by law;
(b) the prohibition of eugenic practices, in particular those aiming at the selection of persons;
(c) the prohibition on making the human body and its parts as such a source of financial gain;
(d) the prohibition of the reproductive cloning of human beings.
The genetic modification of human embryos would violate these provisions.
Another concern with allowing germline modification, even in a limited form, is that it can create a "slippery slope"; if researchers are allowed to use it to limit the transmission of even a few specified diseases, why shouldn't its use be allowed to limit any disease? And if it is allowed to increase well-being by treating disease, why not allow it to increase well-being by "enhancing" non-disease traits? MtDNA plays a critical role in cellular energy production and it is conceivable that if 3-person embryos were made legal that some would propose their creation in order to increase the athletic ability, decrease the risk of obesity, or increase the longevity, for example, of their children.
For much more information on inheritable genetic modification, see here.
Implications for identity
Sharing mitochondrial DNA is certainly less of a genetic contribution than an entire egg or sperm, but it is likely to nonetheless have a profound impact on a child’s phenotype. Such increasing evidence asserts that mitochondria act as much more than "batteries" and do in fact influence the traits that make us who we are.
Of course, identity is also influenced by more than one's phenotype. If successful, this donation will allow a child to live free of otherwise debilitating diseases. It is easy to imagine the human curiosity, gratitude, and connection one would feel to the woman that made this possible. If the procedure is unsuccessful, the emotions and relationship between the child and parents, as well as the donor, could be particularly fraught. In either scenario, the current recommendation that donors remain anonymous could be hard for resulting children.
Furthermore, a child resulting from this technique could feel burdened with the knowledge that his or her genetic make-up is different from that of children conceived from two parents. Some children may feel uncomfortable with the fact that their creation was experimental and that they will be encouraged to participate in follow-up studies throughout their life. Finally, girls will likely be made aware of the possibility that genetic anomalies will be passed on to their own children, and they may feel uncomfortable with the recommendation that they undergo IVF and carry out PGD to ensure this is not the case.
Risks of egg extraction
Egg extraction poses under-studied risks to women, including memory loss, bone ache, seizures, and Ovarian Hyperstimulation Syndrome. Nuclear genome transfer research in the U.S. and U.K. has already required hundreds of eggs from women. Economically disadvantaged women are often specifically targeted as potential egg donors, while the risk to their bodies is routinely downplayed and follow-up care tends to be minimal. Many are concerned that the great need for eggs in order to carry out these techniques will lead to increased exploitation of egg donors. These concerns need to be taken into account when considering the advisability of producing 3-person embryos.
[back to Frequently Asked Questions]
How many people would use this technology?
The techniques that are being considered here will be of potential benefit to only a small number of people. Inherited disease caused by mitochondrial DNA of all kinds, including those not relevant to the proposed procedures, affects 1 in 5,000–10,000 people. Women who have inheritable mitochondrial disease and who want to have children have four other options to avoid passing on mutated mtDNA: adoption, egg donation, prenatal genetic diagnosis, and preimplantation genetic diagnosis. Only a very small number of women who have particularly complicated mutations would have reason to consider using one of the mtDNA techniques now being proposed. In the United Kingdom, for example, it has been estimated that this would number not more than ten to twenty families per year. Although the desire of these families to have a genetically related child is understandable, it needs to be balanced against the implications of opening the door to a new era in which human beings have become artifacts of genetic modification.
[back to Frequently Asked Questions]
Can people use PGD to have a genetically related healthy child?
Women who have mitochondrial disorders can produce eggs that have varying degrees of mutated mitochondria. And it has been shown that an embryo with less than 18% of mutated mtDNA has a 95% or greater chance of being unaffected by mitochondrial disease. Therefore, the use of Preimplantation Genetic Diagnosis (PGD) to choose an embryo with a low level of mitochondrial mutations is a valuable option for women who wish to have a fully genetically related child who is healthy.
The complexity of mitochondrial disorders may mean that PGD is never able to completely eliminate the risk of transmission, but there is increasing evidence that it can drastically reduce the risk for most people.
This method has the additional benefit of being able to screen against mitochondrial disorders caused by nuclear DNA, which account for the majority of cases, so it is of potential use to many more women than "mitochondrial transfer." Although there is still more to learn about this option, numerous clinics now offer it to women with mitochondrial diseases.
The only time PGD may not be an option is if close to 100 percent of a woman’s mitochondrial DNA is mutated (homoplasmy.) However in such rare cases, that woman is likely to be suffering from debilitating illness and pregnancy could pose serious risks to her and her child.
Multiple recent studies have shown the promise of PGD for the prevention of mitochondrial disease:
- [Commentary] The first clinical nuclear transplantation in China: new information about a case reported to ASRM in 2003, Reproductive Biomedicine Online, 2016
- A national perspective on prenatal testing for mitochondrial disease, European Journal of Human Genetics, 2014
- Preimplantation genetic diagnosis in mitochondrial DNA disorders: challenge and success, Journal of Medical Genetics, 2013
- Blastocyst preimplantation genetic diagnosis (PGD) of a mitochondrial DNA disorder, Fertility and Sterility, 2012
- Transmission of Mitochondrial DNA Diseases and Ways to Prevent Them, PLOS Genetics, 2010
- Prospect of preimplantation genetic diagnosis for heritable mitochondrial DNA diseases, Oxford Journals, 2003
Is "mitochondrial donation" similar to other kinds of donation?
The "donation of mitochondria" is a misleading way to discuss this technique, which actually removes the nucleus from one woman's egg and puts it into another woman's egg. This procedure is markedly different from organ donation because it alters every part of a person’s existence as it is in continuous interaction with the rest of their DNA; it can have unforeseen complications later in life; and because it forever changes one’s genetic inheritance. It is also not a decision made for oneself as with using a donated organ. The resulting child would never be able to give free and informed consent for the procedure.
It is misleading to draw ethical, social or medical comparisons between "mitochondria donation" and organ donation.
|Many articles have entirely neglected the fact that this technique is inheritable genetic modification. Additionally, there has been misleading information regarding the current uses, safety, and ramifications of nuclear genome transfer. See here for common misconceptions that have proliferated in the media; see here for information about an article that continues to confuse readers because it is undated; and see here for coverage of a live debate that took place, in which one debater misleadingly used "mitochondria replacement" as an example of why we should oppose a ban on the genetic engineering of babies.|
Media coverage of the recent 3-person IVF birth in Mexico has followed the same trends, downplaying the serious risks involved for the child and future generations (see here). It has lauded the lead doctor, rather than censuring him for conducting unauthorized human experimentation.
[back to Frequently Asked Questions]
Weren't children already born years ago following cytoplasmic transfer (ooplasmic transfer), a similar germline modification technique? What happened with that?
A technique known as cytoplasmic transfer or ooplasmic transfer was used by several fertility clinics between the late 1990s and 2001 to establish as many as 30 pregnancies. It was offered as a way to help infertile women have a child, but was done without any evidence of safety or efficacy, and with no understanding of what "defect" the technique might be correcting.
The FDA reported that of "30 fertilizations achieved after ooplasm transfer ... 13 pregnancies were reported," and of these, "[t]wo fetuses were karyotypically 45, XO (Turner’s syndrome). One of these fetuses aborted spontaneously and the other pregnancy was terminated."
The FDA intervened in 2001, citing concerns about safety and "de facto germline gene transfer." The agency told the fertility clinics offering the procedure that they needed to submit a request for approval before treating additional patients. Apparently no submission was ever made, and the techniques seem to have been abandoned.
In 2014, a couple of the families who had babies after using the technique spoke to the BBC and The New York Times, saying that their child is perfectly normal. The researcher who oversaw these procedures told BBC that one of the babies who seemed fine at birth went on to develop "early signs of pervasive early developmental disorder which is a range of cognitive diseases which also includes autism."
In October 2016, Reproductive BioMedicine Online published the first follow-up study of these children. As the authors state, although the resulting children appear healthy, the study is inconclusive due to a number of serious limitations. The media misinterpreted the study as evidence that not only this specific technique but all forms of 3-person IVF are safe.
Shortly thereafter the journal published “Setting the Record Straight,” its editorial response to the “shoddy scientific journalism” surrounding the article. Critiquing the media's misinterpretation, the editor argued that the technique of cytoplasmic transfer in the late 1990s is so different from 3-person IVF techniques today as to render any comparisons between the two useless.
While cytoplasmic transfer involves a second woman's genes, it is quite different from "mitochondrial transfer." Cytoplasmic transfer involves the injection of a second woman's youthful mitochondria into an infertile woman's egg. Any resulting child would still inherit all of their mother's mitochondrial DNA (mtDNA), but potentially also some mtDNA from the other woman.
"Mitochondrial transfer" on the other hand involves the complete enucleation and transfer of a nucleus from one egg or embryo into another. The goal is for the child to have as close to 100% of the second woman's mtDNA as possible. Therefore, there is reason to believe "mitochondrial transfer" is much riskier, because it could impede with critical fine-tuned mito-nuclear interactions, and because the process of enucleation is more biologically extreme and more likely to cause epigenetic harm.
While it is reassuring to hear that at least some of the small number of children born using cytoplasmic transfer are healthy at this point, it is of limited relevance to the safety of "mitochondrial transfer," and is of no relevance to the efficacy of the latter technique in being able to prevent the transmission of mitochondrial diseases.
An undated Daily Mail article that is actually over a decade old has unfortunately led to a great deal of confusion about the current state of this technique, and of genetically modified humans in general.
Please contact CGS at info[AT]geneticsandsociety[DOT]org to find out more about 3-person IVF, and about how you can make your voice heard in the growing policy debate.
Last modified December 21, 2016