Since the human mitochondrial genome was characterised and sequenced in 1981(1), it has been viewed as the likely site of genetic diseases showing a maternal inheritance pattern and associated with defects of the respiratory chain, such as the mitochondrial myopathies (MMs)†(2). The properties that make it a candidate for the source of such conditions are that it encodes polypeptides involved in electron transport(3,4) and that it is maternally inherited(5). However, several of the mtDNA diseases only fulfill (...) one or other of these criteria: the first group of mtDNA diseases showed Only sporadic deletions(6,7), and the first point mutation in Leber's Hereditary Optic Neuropathy(8) (LHON) is not associated with a clear biochemical defect. Furthermore, it is now clear that both autosomal dominant(9) and probably recessive(10) nuclear genes can cause abnormalities of mtDNA. Each of these major groups will be considered in turn. (shrink)

Mitochondria are essential subcellular organelles containing an extranuclear genome (mtDNA). Mutations in mtDNA have recently been identified as causing a variety of human hereditary diseases. In most of these cases, the tissues of the affected individual contain a mixture of mutant and normal mtDNA, with this ratio determining the severity of symptoms. Stochastic factors alone have generally been believed to determine this ratio. Jenuth et al.(1), however, examining mice that contain a mixture of mtDNA types, show evidence of strong (...) selective forces at work in favoring one mtDNA variant over another in some tissues. (shrink)

Mitochondrial replacement therapy (MRT), also called nuclear genome transfer and mitochondrial donation, is a new technique that can be used to prevent the transmission of mitochondrial DNA diseases. Apart from the United Kingdom, the first country to approve MRT in 2015, Australia became the second country with a clear regulatory path for the clinical applications of this technique in 2021. The rapidly evolving clinical landscape of MRT makes the elaboration and evaluation of the responsible use of (...) this technology a pressing matter. As jurisdictions with less strict or non-existent reproductive laws are continuing to use MRT in the clinical context, the need to address the underlying ethical issues surrounding MRT’s clinical translation is fundamental. (shrink)

Techniques for resolving some types of inherited mitochondrial diseases have recently been the subject of scientific research, ethical scrutiny, media coverage and regulatory initiatives in the UK. Building on research using eggs from a variety of providers, scientists hope to eradicate maternally transmitted mutations in mitochondrial DNA by transferring the nuclear DNA of a fertilised egg, created by an intending mother at risk of transmitting mitochondrial disease, and her male partner, into an enucleated egg provided by (...) another woman. In this article we examine how egg providers for mitochondrial research and therapy have been represented in stakeholder debates. A systematic review of key documents and parliamentary debates shows that the balance of consideration tilts heavily towards therapeutic egg providers; research egg providers have been ignored and rendered invisible. However, mapping the various designations of therapeutic egg providers shows that their role is so heavily camouflaged that they have only an absent presence in discussions. We explore this puzzling ambivalence towards egg providers whose contributions are necessary to the success of current mitochondrial research and proposed therapies. We suggest that labels that diminish the contributions of egg providers serve certain governance objectives in managing possible future claims about, and by, therapeutic egg providers. We demonstrate that the social positioning of research egg providers is entangled within that of therapeutic egg providers which means that the former can also never receive their due recognition. This article contributes to the wider literature on the governance of new technological interventions. (shrink)

The United Kingdom is the first and so far only country to pass explicit legislation allowing for the licensed use of the new reproductive technology known as mitochondrial replacement therapy. The techniques used in this technology may prevent the transmission of mitochondrial DNA diseases, but they are controversial because they involve the manipulation of oocytes or embryos and the transfer of genetic material. Some commentators have even suggested that MRT constitutes germline genome modification. All eyes were on (...) the United Kingdom as the most likely location for the first MRT birth, so it was a shock when, on September 27, 2016, an announcement went out that the first baby to result from use of the intervention had already been born. In New York City, United States-based scientist John Zhang used maternal spindle transfer to generate five embryos for a woman carrying oocytes with deleterious mutations of the mitochondrial DNA. Zhang then shipped the only euploid embryo to Mexico, where it was transferred to the mother's uterus. Zhang's team's travel across international borders to carry out experimental procedures represents a form of scientific tourism that has not been properly ethically explored; it can, however, have seriously detrimental effects for developing countries. (shrink)

In this paper, we argue that lesbian couples who wish to have children who are genetically related to both of them should be allowed access to mitochondrial replacement techniques. First, we provide a brief explanation of mitochondrial diseases and MRTs. We then present the reasons why MRTs are not, by nature, therapeutic. The upshot of the view that MRTs are non-therapeutic techniques is that their therapeutic potential cannot be invoked for restricting their use only to those cases (...) where a mitochondrial DNA disease could be ‘cured’. We then argue that a positive case for MRTs is justified by an appeal to reproductive freedom, and that the criteria to access these techniques should hence be extended to include lesbian couples who wish to share genetic parenthood. Finally, we consider a potential objection to our argument: that the desire to have genetically related kin is not a morally sufficient reason to allow lesbian couples to access MRTs. (shrink)

In 2015 the United Kingdom (UK) became the first nation to legalize egg and zygotic nuclear transfer procedures using mitochondrial replacement techniques (MRTs) to prevent the maternal transmission of serious mitochondrial DNA diseases to offspring. These techniques are a form of human germline genetic modification and can happen intentionally if female embryos are selected during the MRT clinical process, either through sperm selection or preimplantation genetic diagnosis (PGD). In the same year, an MRT was performed by a (...) United States (U.S.)-based physician team. This experiment involved a cross-border effort: the MRT procedure per se was carried out in the US, and the embryo transfer in Mexico. The authors examine the ethics of MRTs from the standpoint of genetic relatedness and gender implications, in places that lack adequate laws and regulation regarding assisted reproduction. Then, we briefly examine whether MRTs can be justified as a reproductive option in the US and Mexico, after reassessing their legalization in the UK. We contend that morally inadequate and ineffective regulations regarding egg donation, PGD, and germline genetic modifications jeopardize the ethical acceptability of the implementation of MRTs, suggesting that MRTs are currently difficult to justify in the US and Mexico. In addition to relevant regulation, the initiation and appropriate use of MRTs in a country require a child-centered follow-up policy and more evidence for its safety. (shrink)

We review a recent paper in Genome Research by Guantes et al. showing that nuclear gene expression is influenced by the bioenergetic status of the mitochondria. The amount of energy that mitochondria make available for gene expression varies considerably. It depends on: the energetic demands of the tissue; the mitochondrial DNA (mtDNA) mutant load; the number of mitochondria; stressors present in the cell. Hence, when failing mitochondria place the cell in energy crisis there are major effects on gene expression (...) affecting the risk of degenerative diseases, cancer and ageing. In 2015 the UK parliament approved a change in the regulation of IVF techniques, allowing “Mitochondrial replacement therapy” to become a reproductive choice for women at risk of transmitting mitochondrial disease to their children. This is the first time that this technique will be available. Therefore understanding the interaction between mitochondria and the nucleus has never been more important. (shrink)

Mitochondrial function is key for maintaining cellular health, while mitochondrial failure is associated with various pathologies, including inherited metabolic disorders and age‐related diseases. In order to maintain mitochondrial quality, several pathways of mitochondrial quality control have evolved. These systems monitor mitochondrial integrity through antioxidants, DNA repair systems, and chaperones and proteases involved in the mitochondrial unfolded protein response. Additional regulation of mitochondrial function involves dynamic exchange of components through mitochondrial fusion and (...) fission. Sustained stress induces a selective autophagy – termed mitophagy – and ultimately leads to apoptosis. Together, these systems form a network that acts on the molecular, organellar, and cellular level. In this review, we highlight how these systems are regulated in an integrated context‐ and time‐dependent network of mitochondrial quality control that is implicated in healthy aging. (shrink)

Abstract Background The first live birth following the use of a new reproductive technique, maternal spindle transfer (MST), which is a mitochondrial replacement technique (MRT), was accomplished by dividing the execution of the MST procedure between two countries, the USA and Mexico. This was done in order to avoid US legal restrictions on this technique. -/- Sources of data Academic articles, news articles, documents obtained through freedom of information requests, laws, regulations and national reports. -/- Areas of agreement MRTs (...) are new reproductive techniques that present novel ethical and legal challenges, since genetic material from three people is employed to create a child. -/- Areas of controversy Could the first MST procedure that culminated in a live birth negatively impact reproductive medicine in Mexico? -/- Growing points The USA and Mexico need specific and clear legislation on MRTs, in order for such techniques not to be governed by prior existing legislation on assisted reproduction that is inadequate for dealing with the new challenges that these techniques present. -/- Areas timely for developing research There is a pressing need for work to be done on the international governance of new reproductive techniques. (shrink)

Mitochondrial DNA (mtDNA) diseases are a group of neuromuscular diseases that often cause suffering and premature death. New mitochondrial replacement techniques (MRTs) may offer women with mtDNA diseases the opportunity to have healthy offspring to whom they are genetically related. MRTs will likely be ready to license for clinical use in the near future and a discussion of the ethics of the clinical introduction ofMRTs is needed. This paper begins by evaluating three concerns about the (...) safety of MRTs for clinical use on humans: (1) Is it ethical to use MRTs if safe alternatives exist? (2) Would persons with three genetic contributors be at risk of suffering? and (3) Can society trust that MRTs will be made available for humans only once adequate safety testing has taken place, and that MRTs will only be licensed for clinical use in a way that minimises risks? It is then argued that the ethics debate about MRTs should be reoriented towards recommendingways to reduce the possible risks of MRT use on humans. Two recommendations are made: (1) licensed clinical access to MRTs should only be granted to prospective parents if they intend to tell their children about their MRT conception by adulthood; and (2) sex selection should be used in conjunction with the clinical use ofMRTs, in order to reduce transgenerational health risks. (shrink)

Children created through mitochondrial replacement techniques (MRTs) are commonly presented as possessing 50% of their mother’s nuclear DNA, 50% of their father’s nuclear DNA and the mitochondrial DNA of an egg donor. This lab-engineered genetic composition has prompted two questions: Do children who are the product of an MRT procedure have threegeneticparents? And, do MRT egg donors have parental responsibilities for the children created? In this paper, I address the second question and in doing so I also address (...) the first one. First, I present a brief account of mitochondrial diseases and MRTs. Second, I examine how MRTs affect the numerical identity of eggs and zygotes. Third, I investigate two genetic accounts of parenthood and MRT egg donation. Fourth, I explore three causal accounts of parenthood and MRT egg donation. My conclusion is that, under the appropriate circumstances, MRT egg donors are parentally responsible for the children created under genetic accounts of parenthood and under causal accounts of parenthood. (shrink)

Technical, ethical, and social questions of germ-line gene interventions have been widely discussed in the literature. The majority of these discussions focus on planned interventions executed on the nuclear DNA (nDNA). However, human cells also contain another set of genes that is the mitochondrial DNA (mtDNA). As the characteristics of the mtDNA grossly differ from those of nDNA, so do the social, ethical, psychological, and safety considerations of possible interventions on this part of the genetic substance.

Mitochondrial replacement techniques (MRTs) have made headlines as some countries have passed legislation permitting the creation of “three-parent embryos” and because of the recent revelation that a child has already been born following the use of these techniques. MRTs assist women with severe mitochondrial disease to have children who are free from mitochondrial disease. Essentially, the mitochondrial DNA of an ovum or embryo is removed and replaced with the mtDNA of a donor. The purpose of this (...) paper is to argue that MRTs are ethically impermissible but greater regulation is needed. There are five parts to this paper: (1) a brief history of mitochondrial manipulation, (2) a description of the MRT process, (3) ethical arguments in opposition to MRTs, (4) relevant counterarguments, and (5) a proposal for increased regulation. (shrink)

Technical, ethical, and social questions of germ-line gene interventions have been widely discussed in the literature. The majority of these discussions focus on planned interventions executed on the nuclear DNA (nDNA). However, human cells also contain another set of genes that is the mitochondrial DNA (mtDNA). As the characteristics of the mtDNA grossly differ from those of nDNA, so do the social, ethical, psychological, and safety considerations of possible interventions on this part of the genetic substance.

Mitochondrial replacement techniques (MRTs) are a new group of biotechnologies that aim to aid women whose eggs have disease-causing deleteriously mutated mitochondria to have genetically related healthy children. These techniques have also been used to aid women with poor oocyte quality and poor embryonic development, to have genetically related children. Remarkably, MRTs create humans with DNA from three sources: nuclear DNA from the intending mother and father, and mitochondrial DNA from the egg donor. In a recent publication Françoise (...) Baylis argued that MRTs are detrimental for genealogical research via mitochondrial DNA because they would obscure the lines of individual descent. In this paper, I argue that MRTs do not obscure genealogical research, but rather that MRT-conceived children can have two mitochondrial lineages. I argue for this position by showing that MRTs are reproductive in nature and, thus, they create genealogy. (shrink)

Mitochondrial donation or mitochondrial transfer enables a woman with mitochondrial disease to have a genetically related child without transmitting the disease to the child. The techniques used for mitochondrial donation or transfer which are maternal spindle transfer or pro-nuclei transfer, require three gametes to ultimately produce a healthy embryo. Both these techniques result in the child inheriting nuclear DNA from the intending parents and mitochondrial DNA from the female donor. Following the legalisation of mitochondrial (...) donation in the UK, after a rigorous process of scientific and ethical review, and the birth of another baby using the technique, coupled with the fact that there is no cure for mitochondrial disease, suggests that it is prudent for us to consider this reproductive intervention and its application in the South African setting. In addition, the 2019 UNESCO Report of the International Bioethics Committee (IBC) on assisted reproductive technologies (ART) and parenthood, encourages debate on changes in models of parenthood influenced by ART including the emergence of new models of families and forms of parenthood that extend beyond the classical rule of mater semper certa est (the mother is always known). ART, in particular mitochondrial donation, challenges this rule. The aim of this paper is to provide an outline of the legal and ethical positions of mitochondrial donation and resume the discussion with specific focus on the South African context. (shrink)

In April 2007, as part of its public consultation initiative, the Human Fertilisation and Embryology Authority in the United Kingdom published Hybrids and chimeras: A consultation on the ethical and social implications of creating human/animal embryos in research. This HFEA document identifies a number of possible arguments against the creation of human/animal embryos. One of these arguments concerns the worry that human/animal embryos “might be transferred to a woman to create babies with some animal DNA in them.” Although the HFEA (...) dismisses this slippery slope argument, I argue that this possible future is not as farfetched as one might think. For example, human admixed embryos might be transferred to women in an effort to prevent the transmission of mitochondrial diseases. The ethical acceptability of this possible future practice is examined from different feminist perspectives with a focus on issues of reproductive freedom and social justice. (shrink)

As individuals enter their 80s, they are inevitably confronted with the problem of neuronal loss in the brain. The incidence of the common movement disorder ‘mild parkinsonian signs’ (MPS) is approximately 50% over the age of 85 years. It has long been known that the loss of dopaminergic neurons in the substantia nigra pars compacta is a neuropathological hallmark of Parkinson's disease (PD). Recently, two papers1,2 present clear evidence for a high burden of mitochondrial DNA deletions within substantia nigra (...) neurons in aged individuals and individuals with PD, pointing towards a common pathway inevitably leading to neuronal dysfunction and death. BioEssays 28: 963–967, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

ObjectiveTo elucidate the clinical, radiologic characteristics of Leber’s hereditary optic neuropathy (LHON) associated with the other diseases.Materials and methodsClinical data were retrospectively collected from hospitalized patients with LHON associated with the other diseases at the Neuro-Ophthalmology Department at the Chinese People’s Liberation Army General Hospital (PLAGH) from December 2014 to October 2018.ResultsA total of 13 patients, 24 eyes (10 men and 3 women; mean age, 30.69 ± 12.76 years) with LHON mitochondrial DNA (mtDNA) mutations, were included in (...) the cohort. 14502(5)11778(4)11778 &11696(1)12811(1)11696(1)3460(1). One patient was positive for aquaporin-4 antibody (AQP4-Ab), and two were positive for myelin oligodendrocyte glycoprotein antibody (MOG-Ab). Three patients were associated with idiopathic optic neuritis (ON). Two patients were with compression optic neuropathy. Three patients were with the central nervous system (CNS) diseases. One patient was with proliferative diabetic retinopathy (PDR) and one with idiopathic orbital inflammatory syndrome (IOIS). At the onset, visual acuity (VA) in eighteen eyes was below 0.1, one eye was 0.5, five eyes were above 0.5, while VA in sixteen eyes was below a 0.1 outcome, three eyes experienced moderate vision loss. MRI images showed T2 lesions and enhancement in nine patients who received corticosteroids treatment; additional immune modulators treatment was performed on two patients. None of the patients had relapse during the follow-up time.ConclusionLeber’s hereditary optic neuropathy can be accompanied with multiple-related diseases, especially different subtypes of ON, which were also exhibited with IOIS and compression optic neuropathy for the first time in this cohort. This condition may be a distinct entity with an unusual clinical and therapeutic profile. (shrink)

Mitochondrial DNA (mtDNA) mutations escalate with increasing age in higher organisms. However, it has so far been difficult to experimentally determine whether mtDNA mutation merely correlates with age or directly limits lifespan. A recent study shows that budding yeast can also lose functional mtDNA late in life. Interestingly, independent studies of replicative lifespan (RLS) and of mtDNA‐deficient cells show that the same mutations can increase both RLS and the division rate of yeast lacking the mitochondrial genome. These exciting, (...) parallel findings imply a potential causal relationship between mtDNA mutation and replicative senescence. Furthermore, these results suggest more efficient methods for discovering genes that determine lifespan. (shrink)

Mammalian mitochondrial DNA (mtDNA) replication and repair have been studied intensively for the last 50 years. Although recently advances in elucidating the molecular mechanisms of mtDNA maintenance and the proteins involved in these have been made, there are disturbing gaps between the existing theoretical models and experimental observations. Conflicting data and hypotheses exist about the role of RNA and ribonucleotides in mtDNA replication, but also about the priming of replication and the formation of pathological rearrangements. In the presented review, (...) we have attempted to match these loose ends and draft consensus where it can be found, while identifying outstanding issues for future research. (shrink)

Mammalian mitochondrial DNA (mtDNA) replication and repair have been studied intensively for the last 50 years. Although recently advances in elucidating the molecular mechanisms of mtDNA maintenance and the proteins involved in these have been made, there are disturbing gaps between the existing theoretical models and experimental observations. Conflicting data and hypotheses exist about the role of RNA and ribonucleotides in mtDNA replication, but also about the priming of replication and the formation of pathological rearrangements. In the presented review, (...) we have attempted to match these loose ends and draft consensus where it can be found, while identifying outstanding issues for future research. (shrink)

Mitochondria exist in large numbers per cell. Therefore, the strength of natural selection on individual mtDNAs for their contribution to cellular fitness is weak whereas the strength of selection in favor of mtDNAs that increase their own replication without regard for cellular functions is strong. This problem has been solved for most mitochondrial genes by their transfer to the nucleus but a few critical genes remain encoded by mtDNA. Organisms manage the evolution of mtDNA to prevent mutational decay of (...) essential services mitochondria provide to their hosts. Bottlenecks of mitochondrial numbers in female germlines increase the homogeneity of mtDNAs within cells and allow intraorganismal selection to eliminate cells with low quality mitochondria. Mechanisms of intracellular “quality control” allow direct selection on the competence of individual mtDNAs. These processes maintain the integrity of mtDNAs within the germline but are inadequate to indefinitely maintain mitochondrial function in somatic cells. (shrink)

The proliferation of mitochondrial DNA (mtDNA) with deletion mutations has been linked to aging and age related neurodegenerative conditions. In this study we model the effect of mtDNA half-life on mtDNA competition and selection. It has been proposed that mutation deletions (mtDNAdel\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{del}$$\end{document}) have a replicative advantage over wild-type (mtDNAwild\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{wild}$$\end{document}) and that this is detrimental to the host cell, especially in (...) post-mitotic cells. An individual cell can be viewed as forming a closed ecosystem containing a large population of independently replicating mtDNA. Within this enclosed environment a selfishly replicating mtDNAdel\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{del}$$\end{document} would compete with the mtDNAwild\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{wild}$$\end{document} for space and resources to the detriment of the host cell. In this paper, we use a computer simulation to model cell survival in an environment where mtDNAwild\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{wild}$$\end{document} compete with mtDNAdel\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{del}$$\end{document} such that the cell expires upon mtDNAwild\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{wild}$$\end{document} extinction. We focus on the survival time for long lived post-mitotic cells, such as neurons. We confirm previous observations that mtDNAdel\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{del}$$\end{document} do have a replicative advantage over mtDNAwild\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{wild}$$\end{document}. As expected, cell survival times diminished with increased mutation probabilities, however, the relationship between survival time and mutation rate was non-linear, that is, a ten-fold increase in mutation probability only halved the survival time. The results of our model also showed that a modest increase in half-life had a profound affect on extending cell survival time, thereby, mitigating the replicative advantage of mtDNAdel\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {mtDNA}_{del}$$\end{document}. Given the relevance of mitochondrial dysfunction to various neurodegenerative conditions, we propose that therapies to increase mtDNA half-life could significantly delay their onset. (shrink)

This manuscript reviews recent evidence supporting the utility of telomeres and mitochondrial DNA copy number (mtDNAcn) in detecting the biological impacts of adverse childhood experiences (ACEs) and outlines mechanisms that may mediate the connection between early stress and poor physical and mental health. Critical to interrupting the health sequelae of ACEs such as abuse, neglect, and neighborhood disorder, is the discovery of biomarkers of risk and resilience. The molecular markers of chronic stress exposure, telomere length and mtDNAcn, represent critical (...) biological links between ACEs and poor health outcomes. We examine how telomeres and mtDNAcn may exacerbate health disparities and contribute to the intergenerational transmission of trauma. Finally, we explore how these molecular markers of early stress exposure may help define the role of resilience and develop effective interventions to moderate ACE health risk impact. (shrink)

Evidence for recombination suppression has been identified in linkage studies of several unstable DNA diseases. Also sex‐specific changes in recombination frequency have been detected at the loci of Huntington's disease and myotonic dystrophy. It can be hypothesized that meiotic recombination is regulated by genome‐wide genomic imprinting and that changes in meiotic recombination imply the presence of the genomic imprinting defect. If aberrant recombination at the locus of trinucleotide repeat expansion is verified, new theoretical and experimental opportunities will arise in (...) studies on the role of genomic imprinting in the unstable DNA diseases. (shrink)

This paper examines whether there are moral differences between the mitochondrial replacement techniques that have been recently developed in order to help women afflicted by mitochondrial DNA diseases to have genetically related children absent such conditions: maternal spindle transfer and pronuclear transfer. Firstly, it examines whether there is a moral difference between MST and PNT in terms of the divide between somatic interventions and germline interventions. Secondly, it considers whether PNT and MST are morally distinct under a (...) therapy/creation optic. Finally, it investigates whether there is a moral difference between MST and PNT from a human embryo destruction point of view. I conclude, contra recent arguments, that regarding the first two points there is no moral differences between PNT and MST; and that regarding the third one MST is morally preferable to PNT, but only if we hold a gradualist account of the moral value of human embryos where zygotes have slight moral value. (shrink)

The organisation of mammalian mitochondrial DNA (mtDNA) is more complex than usually assumed. Despite often being depicted as a simple circle, the topology of mtDNA can vary from supercoiled monomeric circles over catenanes and oligomers to complex multimeric networks. Replication of mtDNA is also not clear cut. Two different mechanisms of replication have been found in cultured cells and in most tissues: a strand‐asynchronous mode involving temporary RNA coverage of one strand, and a strand‐coupled mode rather resembling conventional nuclear (...) DNA replication. In addition, a recombination‐initiated replication mechanism is likely to be associated with the multimeric mtDNA networks found in human heart. Although an insight into the general principles and key factors of mtDNA organisation and maintenance has been gained over the last few years, there are many open questions regarding replication initiation, termination and physiological factors determining mtDNA organisation and replication mode. However, common themes in mtDNA maintenance across eukaryotic kingdoms can provide valuable lessons for future work. (shrink)

In February 2016, the Institute of Medicine released a report, commissioned by the United States Food and Drug Administration, on the ethical and social‐policy implications of so‐called three‐parent in vitro fertilization. The IOM endorses commencement of clinical trials on three‐parent IVF, subject to some initial limitations. Also called mitochondrial replacement or transfer, three‐parent IVF is an intervention comprising two distinct procedures in which the genetic materials of three people—the DNA of the father and mother and the mitochondrial DNA (...) of an egg donor—can be used to create a child. Three‐parent IVF would enable a woman with mitochondrial disease to have a genetically related child without transmitting the disease to the child. The possibility for three‐parent children has prompted criticism from many corners. Critics have pointed to ethical issues including safety concerns and risks to children, genetic and germline engineering concerns, the potential exploitation of the third‐parent egg donor, donor anonymity and privacy, and objections to creating babies with three parents, which undermines natural and traditional conceptions of procreation. Additionally, developing the technology would involve experimenting on, manipulating, and disposing of embryos. Although the IOM report considers the ethical concerns about the value of the three‐parent IVF technology, the IOM failed to give due attention to an important objection to the development of this technology: three‐parent IVF lacks the social value necessary to make investment of public resources in it ethical.Unlike the other concerns, this objection is not based on conservativism about new reproductive technologies or default favoritism of the status quo. I argue that the technology does not meet a plausible social value standard to render public research investment into its development ethical. Proponents of three‐parent IVF make inaccurate and exaggerated claims that it will eradicate mitochondrial disease and save lives. Were these claims true, proponents would have a strong case for the social value of the technology. But three‐parent IVF alone will not eradicate mitochondrial disease, and it will not save lives. Rather, it can create healthy lives. As I discuss, the moral distinction is crucial. Most importantly, investment in three‐parent IVF comes at the opportunity cost of researching treatment for mitochondrial disease that would benefit actual, living disease sufferers. (shrink)

Molecular genetic data have greatly improved our ability to test hypotheses about human evolution. During the past decade, a large amount of nuclear and mitochondrial data have been collected from diverse human populations. Taken together, these data indicate that modern humans are a relatively young species. African populations show the largest amount of genetic diversity, and they are the most genetically divergent population. Modern human populations expanded in size first on the African continent. These findings support a recent African (...) origin of modern humans, but this conclusion should be tempered by the possible effects of factors such as gene flow, population size differences, and natural selection. BioEssays 20:126–136, 1998. © 1998 John Wiley & Sons, Inc. (shrink)

Mitochondria contain a molecular genetic system to express the 13 protein components of the electron transport system encoded in the mitochondrial genome (mtDNA). Defects in the function of this system result in some diaseases, many of which are multisystem disorders, prominently involving highly aerobic, postmitotic tissues. These defects can be caused by large‐scale rearrangements of mtDNA, by point mutations, or by nuclear gene mutations resulting in abnormalities in mtDNA. Although any of these mutations would be expected to produce a (...) similar clinical phenotype by compromising oxidative phosphorylation, the surprising and puzzling result is that different clinical phenotypes are generally associated with specific mtDNA mutations. Moreover, the same mutation can produce a distinct clinical phenotype in different individuals or pedigrees. MtDNA rearrangements are also found in aged individuals, but at a subclinical level, suggesting that normal and pathological processes can differ by the effect of genetic or environmental factors on the error rate of mtDNA replication. (shrink)

The parents of Charlie Gard, who was born August 4, 2016, with an exceedingly rare and incurable disease called mitochondrial DNA depletion syndrome, fought a prolonged and heated legal battle to allow him access to experimental treatment that they hoped would prolong his life and to prevent his doctors from withdrawing life-sustaining care. Charlie's clinicians at the Great Ormond Street Hospital in London believed that the brain damage Charlie had suffered as a result of frequent epileptic seizures, along with (...) many other severe disabilities, would render any innovative therapy futile, and they disagreed with his parents’ wishes to use an experimental therapy. They felt it in Charlie's best interest that he be allowed to die. A battle ensued among Charlie's parents, his doctors, and a guardian who had been appointed to represent him that drew the attention of politicians and prominent persons from all over the world. The case was much in the news over the past year, but it has also been frequently misunderstood. (shrink)

On September 27, 2016 people across the world looked down at their buzzing phones to see the AP Alert: “Baby born with DNA from 3 people, first from new technique.” It was an announcement met with confusion by many, but one that polarized the scientific community almost instantly. Some celebrated the birth as an advancement that could help women with a family history of mitochondrial diseases prevent the transmission of the disease to future generations; others held it unethical, (...) citing medical tourism and consequences for the future of the therapy. The child in question was actually born a few months earlier on April 6, 2016, but the research was published a few months later in the October edition of Fertility and Sterility. The mother carries DNA that could have given the baby Leigh Syndrome, a severe neurological disorder characterized by psychomotor regression that typically results in death between ages two and three.[1] Also known as subacute necrotizing encephalomyelopathy, Leigh Syndrome is caused by genetic mutations in mitochondrial DNA, which causes defective oxidative phosphorylation. Because people with this condition cannot re-form ATP, “demyleniation, gliosis, necrosis, spongiosis, or capillary proliferation”[2] can occur, thereby producing bilateral lesions across the central nervous system. The 36-year-old mother previously had four miscarriages and successfully birthed two children, both of whom survived less than six years due to the syndrome. For religious reasons, the mother opted for Spindle Nuclear Transfer instead of Pronuclear Transfer,[3] which many religious organizations oppose because it entails the destruction of fertilized eggs.[4] In Pronuclear Transfer, both the parent and donor egg are fertilized. The parent’s nuclear material is then removed from the egg containing mutated mitochondria and inserted into the fertilized donor egg—from which the original nuclear material has been removed and destroyed. Spindle Nuclear Transfer, on the other hand, removes the mother’s nuclear material from the egg with unhealthy mitochondria, then implants it into a donor’s egg. The newly created egg is then fertilized with the father’s sperm. This Spindle Nuclear Transfer was performed in Mexico by a team of doctors led by Dr. John Zhang, the founder of the New Hope Fertility Center in New York City. In their report, the doctors outline that five oocytes were successfully reconstituted, four of which developed into blastocysts. Only one was euploid: containing 46 XY chromosomes. Researchers then biopsied that blastocyst and found that the transmission rate of maternal mtDNA was, “5.10 ± 1.11% and the heteroplasmy level for 8993T>G was 5.73%.”[5] This indicates that at the blastocyst stage, around five percent of the mitochondria are from the original maternal egg with the mutation for Leigh Syndrome. After birth, they biopsied different tissues and found that they had an average of less than 1.60 ± 0.92% of transmitted mtDNA from the original maternal egg. The baby is reportedly doing well and the team of doctors concluded that “[h]uman oocytes reconstituted by SNT are capable of producing a healthy live birth. SNT may provide a novel treatment option in minimizing pathogenic mtDNA transmission from mothers to their babies."[6] Even when considered theoretically, Spindle Nuclear Transfer is controversial. Many doctors believe that the risks at this stage of research are too great. Dr. Trevor Stammers, a bioethicist at St. Mary’s University in London, points out: “We do not yet have a clear picture of the interaction between nuclear DNA and mitochondria.”[7] Others hold that faulty mitochondrial DNA can still be transferred during the procedure. Still more argue this technology could create problems because of germline modification.[8] Dr. Paul Knoepfler, a cell biologist at the UC Davis School of Medicine, explains: “Since this is uncharted territory and the children born from this technology would have heritable genetic changes, there are also significant unknown risks to future generations.”[9] However, proponents counter these arguments. They say the benefits outweigh the risks, as “mitochondrial replacement techniques [like Spindle Nuclear Transfer] would eliminate maternal transmission of mitochondrial disease… allowing a woman with a family history of mitochondrial diseases to ensure her children would not be affected.”[10] Additionally, experts say that no symptoms will occur if less than 20% of the transferred mitochondrial DNA is faulty.[11] And while opponents see potential germline modification as a problem, advocates answer that this could stop a family history of mitochondrial disease, which they deem a more serious concern. In this case specifically, however, there are more issues at hand. While the team of doctors did eliminate the possibility of germline modification by selecting a male embryo, there are other ethical concerns. Some argue that this case could be described as “medical tourism.” While New Hope Medical Clinic does maintain a branch in Mexico, Dr. Zhang stated that Mexico has “no rules.”[12] It is a country with underdeveloped regulations, making it difficult to confirm that doctors adhere to widely-held medical and ethical standards. Furthermore, while it is highly unlikely that the child will develop Leigh’s Syndrome, Dr. Dietrich Egli of the New York Stem Cell Foundation says the 5% mitochondrial transfer rate indicates that the technique “was not carried out well.”[13] He points to studies of embryos where the rate of mtDNA transfer was almost ten times lower. Spindle Nuclear Transfer is currently legal in the UK,[14] and many are hoping to see it legalized in the US, although Congress currently prohibits the FDA from considering applications that would entail trials in people.[15] While Dr. Zhang’s work is arguably revolutionary, many wonder if the manner in which this study was performed—in Mexico and with a high mitochondrial transfer rate—will impact the technology’s future in the US. Last week, Dr. Zhang presented the report to scientists gathered in Salt Lake City, saying that while science isn’t a race, it is “in a sense, a race for the family to find a cure, to find hope.”[16] Only time will tell if this study set back other families racing and hoping for a cure. References 1. "Leigh Syndrome." Genetics Home Reference, US National Library of Medicine, 25 Oct. 2016. Accessed 26 Oct. 2016. 2. McKusick, Victor A., and Ada Hamosh. "LEIGH SYNDROME; LS." Online Mendelian Inheritance in Man, Johns Hopkins University, 20 Jan. 2016. Accessed 30 Oct. 2016. 3. Zhang, J, H Liu, S Luo, A Chavez-Badiola, and Z Liu. "First live birth using human oocytes reconstituted by spindle nuclear transfer for mitochondrial DNA mutation causing Leigh syndrome." Fertility and Sterility, vol. 106, no. 3, 2016, pp. e375-76. Accessed 30 Oct. 2016. 4. Sample, Ian. "‘Three-parent’ babies explained: what are the concerns and are they justified?" The Guardian, 2 Feb. 2015. Accessed 30 Oct. 2016. 5. Zhang, et al. 6. Ibid. 7. Knapton, Sarah. "Three-parent babies: the arguments for and against." The Telegraph, 3 Feb. 2015. 8. Ibid. 9. Ibid. 10. "Mitochondrial Replacement Therapy FAQs." New York Stem Cell Foundation Research Institute, New York Stem Cell Foundation. Accessed 30 Oct. 2016. 11. Reardon, Sara. "‘Three-parent baby’ claim raises hopes — and ethical concerns." Nature, 28 Sept. 2016. Accessed 30 Oct. 2016. 12. Hamzelou, Jessica. "Exclusive: World’s first baby born with new “3 parent” technique." New Scientist, 27 Sept. 2016. Accessed 30 Oct. 2016. 13. Reardon, Sara. "‘Three-parent baby’ claim raises hopes — and ethical concerns." Nature, 28 Sept. 2016. Accessed 30 Oct. 2016. 14. "3-Person IVF: A Resource Page." Center for Genetics and Society, 24 Oct. 2016. Accessed 30 Oct. 2016. 15. Ritter, Malcolm. "Baby born with DNA from 3 people, first from new technique." Associated Press, 27 Sept. 2016. Accessed 30 Oct. 2016. 16. Chen, Daphne. "Controversy swirls around first three-parent baby." Deseret News, 19 Oct. 2016. Accessed 30 Oct. 2016. Works consulted Swetlitz, Ike. "FDA urged to approve ‘three-parent embryos,’ a new frontier in reproduction." STAT, 3 Feb. 2016. Accessed 30 Oct. 2016. (shrink)

The major mechanism of repair of damage to DNA involves a conceptually simple process of enzymatic excision and resynthesis of small regions of DNA. In man and other mammals, this process is regulated by several gene loci; up to 15 mutually complementary genes or gene products may be involved. Repair deficiency results in an array of clinical symptoms in skin, central nervous system, and hematopoietic and immune systems, the major example being xeroderma pigmentosum (XP), a disease with a high incidence (...) of cancer. Cloning repair genes by straightforward methods has proved difficult, but we have begun the effort by demonstrating that correction of a human repair deficiency can be achieved by transferring very small fragments of DNA from normal hamsters into XP cells. One of the complementation groups of XP cells (group C) appears to express a change in gene regulation such that these cells repair only a small clustered region of the DNA with high efficiency. (shrink)

We argue that the most‐promising area of clinical application of microarrays in the foreseeable future is the diagnostics and monitoring of infectious diseases. Microarrays for the detection and characterization of human pathogens have already found their way into clinical practice in some countries. After discussing the persistent, yet often underestimated, importance of infectious diseases for public health, we consider the technologies that are best suited for the detection and clinical investigation of pathogens. Clinical application of microarray technologies for (...) the detection of mycobacteria, Bacillus anthracis, HIV, hepatitis and influenza viruses, and other major pathogens, as well as the analysis of their drug‐resistance patterns, illustrate our main thesis. BioEssays 30:673–682, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Under the putative influence of dietary selection pressure, the subcellular distribution of alanine:glyoxylate aminotransferase 1 (AGT) has changed on many occasions during the evolution of mammals. Depending on the particular species, AGT can be found either in peroxisomes or mitochondria, or in both peroxisomes and mitochondria. This variable localization depends on the differential expression of N‐terminal mitochondrial and C‐terminal peroxisomal targeting sequences by the use of alternative transcription and translation initiation sites. AGT is peroxisomal in most humans, but it (...) is mistargeted to the mitochondria in a subset of patients suffering from the rare herediatry disease primary hyperoxaluria type 1. Mistargeting is due to the unlikely combination of a normally occurring polymorphism that generates a functionally weak mitochondrial targeting sequence and a disease‐specific mutation which, in combination with the polymorphism, inhibits AGT dimerization. The mechanisms by which AGT can be targeted differentially to peroxisomes and/or mitochondria highlight the different molecular requirements for protein import into these two organelles. (shrink)

In October 2015 the UK enacted legislation to permit the clinical use of two cutting edge germline-altering, IVF-based embryonic techniques: pronuclear transfer and maternal spindle transfer. The aim is to use these techniques to prevent the maternal transmission of serious mitochondrial diseases. Major claims have been made about the quality of the debates that preceded this legislation and the significance of those debates for UK decision-making on other biotechnologies, as well as for other countries considering similar legislation. In (...) this article we conduct a systematic analysis of those UK debates and suggest that claims about their quality are over-stated. We identify, and analyse in detail, ten areas where greater clarity, depth and nuance would have produced sharper understandings of the contributions, limitations and wider social impacts of these mitochondrial interventions. We explore the implications of these additional considerations for the protection of all parties involved, should the techniques transfer to clinical applications; the legitimacy of focussing on short-term gains for individuals over public health considerations, and the maintenance and improvement of public trust in medical biotechnologies. We conclude that a more measured evaluation of the content and quality of the UK debates is important and timely: such a critique provides a clearer understanding of the possible, but specific, contributions of these interventions, both in the UK and elsewhere; also, these additional insights can now inform the emerging processes of implementation, regulation and practice of mitochondrial interventions. (shrink)

Mitochondrial replacement techniques are intended to avoid the transmission of mitochondrial diseases from mother to child. MRT represent a potentially powerful new biomedical technology with ethical, policy, economic and social implications. Among other ethical questions raised are concerns about the possible effects on the identity of children born from MRT, their families, and the providers or donors of mitochondria. It has been suggested that MRT can influence identity directly, through altering the genetic makeup and physical characteristics of (...) the child, or indirectly through changing the child's experience of disease, and by generating novel intrafamilial relationships that shape the sense of self. In this article I consider the plausibility and ethical implications of these proposed identity effects, but I focus instead on a third way in which identity may be affected, through the mediating influence of the wider social world on MRT effects on identity. By taking a narrative approach, and examining the nature and availability of identity narratives, I conclude that while neither direct genetic nor indirect experiential effects can be excluded, social responses to MRT are more likely to have a significant and potentially damaging influence on the generation of MRT children's narratives of identity. This conclusion carries some implications for the collective moral responsibility we hold to ensure that MRT, if implemented, are practised in ethically justifiable ways. (shrink)

Mitochondrial replacement technology (MRT) is an emerging and complex bioethical issue. This treatment aims to eliminate maternal inherited mitochondrial DNA (mtDNA) disorders. For Muslims, its introduction affects every aspect of human life, especially the five essential interests of human beings—namely, religion, life, lineage, intellect, and property. Thus, this technology must be assessed using a comprehensive and holistic approach addressing these human essential interests. Consequently, this article analyses and assesses tri-parent baby technology from the perspective of Maqasidic bioethics—that is, (...) Islamic bioethics based on the framework of Maqasid al-Shariah. Using this analysis, this article suggests that tri-parent baby technology should not be permitted for Muslims due to the existence of third-party cell gametes which lead to lineage mixing and due to the uncertain safety of the therapy itself and because the major aim of the technology is to fulfil the affected couples interest to conceive their own genetically healthy child, not to treat and cure mtDNA disorders sufferers. (shrink)

Taking advantage of the fact that they need not replicate their DNA, terminally differentiated neurons only repair their expressed genes and largely dispense with the burden of removing damage from most of their genome. However, they may pay a heavy price for this laxity if unforeseen circumstances, such as a pathological condition like Alzheimer's disease, cause them to re‐enter the cell cycle. The lifetime accumulation of unrepaired lesions in the silent genes of neurons is likely to be significant and may (...) result in aborting the mitotic process and triggering cell death if the cells attempt to express these dormant genes and resume DNA replication. BioEssays 25:168–173, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

Mitochondrial/nuclear transfer (M/NT) to avoid the transmission of serious mitochondrial disease raises complex and challenging ethical, legal and social issues (ELSI). In February 2015, the United Kingdom became the first country in the world to legalize M/NT, making the heated debate surrounding this technology even more relevant. This critical interpretive review identified 95 relevant papers discussing the ELSI of M/NT, including original research articles, government-commissioned reports, editorials, letters to editors and research news. The review presents and synthesizes the (...) arguments present in the literature in relation to the most commonly raised themes: terminology; identity, relationships and parenthood; potential harm; reproductive autonomy; available alternatives; consent; impact on specific interest groups; resources; “slippery slope”; creation, use and destruction of human embryos; and beneficence. The review concludes by identifying those ELSI that are specific to M/NT and by calling for follow-up longitudinal clinical and psychosocial research in order to equip future ELSI debate with empirical evidence. (shrink)

This article argues that two forms of mitochondrial replacement therapy, maternal spindle transfer and pro-nuclear transfer, are not therapies at all because they do not treat children who are coming into existence. Rather, these technologies merely create healthy children where none was inevitable. Even if creating healthy lives has some value, it is not to be confused with the medical value of a cure or therapy. The article addresses a recent Bioethics article, ‘Mitochondrial Replacement: Ethics and Identity,’ by (...) Wrigley, Wilkinson, and Appleby, who argue that PNT is morally favorable to MST due to the Non-Identity Problem. Wrigley et al. claim that PNT, since it occurs post-conception, preserves the identity of the resulting child, whereas MST, since it occurs pre-conception, is an identity-altering technique. As such, a child born with mitochondrial disease could complain that her parents failed to use PNT, but not MST. The present article argues that the authors are mistaken: both MST and PNT are identity-affecting techniques. But this is of little matter, for we should be cautious in drawing any moral conclusions from the application of the Non-Identity Problem to cases. The article then argues that the authors are mistaken in inferring that PNT is a type of embryonic cure or therapy for children with mitochondrial disease. The article cautions against the mistaken life-saving rhetoric that is common in bioethics discussions of MRTs. (shrink)

Mitochondrial replacement techniques, known in the popular media as 'three-parent' or 'three-person' IVFs, have the potential to enable women with mitochondrial diseases to have children who are genetically related to them but without such diseases. In the debate regarding whether MRTs should be made available, an issue that has garnered considerable attention is whether MRTs affect the characteristics of an existing individual or whether they result in the creation of a new individual, given that MRTs involve (...) the genetic manipulation of the germline. In other words, do MRTs affect the qualitative identity or the numerical identity of the resulting child? For instance, a group of panelists on behalf of the UK Human Fertilisation and Embryology Authority has claimed that MRTs affect only the qualitative identity of the resulting child, while the Working Group of the Nuffield Council on Bioethics has argued that MRTs would create a numerically distinct individual. In this article, I shall argue that MRTs do create a new and numerically distinct individual. Since my explanation is different from the NCOB's explanation, I shall also offer reasons why my explanation is preferable to the NCOB's explanation. (shrink)