Human germline genetic modification: scientific and bioethical perspectives

Modular Ontologies for Genetically Modified People and their Bioethical Implications

Participants in the long-running bioethical debate over human germline genetic modification (HGGM) tend to imagine future people abstractly and on the basis of conventionalized characteristics familiar from science fiction, such as intelligence, disease resistance and height. In order to distinguish these from scientifically meaningful terms like "phenotype" and "trait," this article proposes the term "persemes" to describe the units of difference for hypothetical people. In the HGGM debate, persemes are frequently conceptualized as similar, modular entities, like building blocks to be assembled into genetically modified people. They are discussed as though they each would be chosen individually without affecting other persemes and as though they existed as components within future people rather than being imposed through social context. This modular conceptual framework appears to influence bioethical approaches to HGGM by reinforcing the idea of human capacities as natural primary goods subject to distributive justice and supporting the use of objective list theories of well-being. As a result, assumptions of modularity may limit the ability of stakeholders with other perspectives to present them in the HGGM debate. This article examines the historical trends behind the modular framework for genetically modified people, its likely psychological basis, and its philosophical ramifications.

Germline genome editing of human IVF embryos should not be subject to overly stringent restrictions

This paper critiques the restrictive criteria for germline genome editing recently proposed by Chin, Nguma, and Ahmad in this journal. While praising the authors for resisting fervent calls for an outright ban on clinical applications of the technology, this paper argues that their approach is nevertheless unduly restrictive, and may thus hinder technological progress. This response advocates for weighing potential benefits against risks without succumbing to excessive caution, proposing that ethical oversight combined with genetic scrutiny at the embryo stage post-editing can enable responsible use of the technology, ultimately reducing the burden of genetic diseases and enhancing human health, akin to how IVF transformed reproductive medicine despite strong initial opposition.

Human Germline Genome Editing: On the Nature of Our Reasons to Genome Edit

Ever since the publication of Derek Parfit's Reasons and Persons, bioethicists have tended to distinguish between two different ways in which reproductive technologies may have implications for the welfare of future persons. Some interventions harm or benefit particular individuals: they are "person affecting." Other interventions determine which individual, of a number of possible individuals, comes into existence: they are "identity affecting" and raise the famous "non-identity problem." For the past several decades, bioethical debate has, for the most part, proceeded on the assumption that direct genetic modification of human embryos would be person affecting. In this paper, I argue that that genome editing is highly unlikely to be person affecting for the foreseeable future and, as a result, will neither benefit nor harm edited individuals.

Should germline genome editing be allowed? The effect of treatment characteristics on public acceptability

STUDY QUESTION

To what extent do characteristics of germline genome editing (GGE) determine whether the general public supports permitting the clinical use of GGE?

SUMMARY ANSWER

The risk that GGE would cause congenital abnormalities had the largest effect on support for allowing GGE, followed by effectiveness of GGE, while costs, the type of application (disease or enhancement) and the effect on child well-being had moderate effects.

WHAT IS KNOWN ALREADY

Scientific progress on GGE has increased the urgency of resolving whether and when clinical application of GGE may be ethically acceptable. Various expert bodies have suggested that the treatment characteristics will be key in determining whether GGE is acceptable. For example, GGE with substantial risks (e.g. 15% chance of a major congenital abnormality) may be acceptable to prevent a severe disease but not to enhance non-medical characteristics or traits of an otherwise healthy embryo (e.g. eye colour or perhaps in the future more complex traits, such as intelligence). While experts have called for public engagement, it is unclear whether and how much the public acceptability of GGE is affected by the treatment characteristics proposed by experts.

STUDY DESIGN, SIZE, DURATION

The vignette-based survey was disseminated in 2018 among 1857 members of the Dutch general public. An online research panel was used to recruit a sample representing the adult Dutch general public.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A literature review identified the key treatment characteristics of GGE: the effect on the well-being of the future child, use for disease or enhancement, risks for the future child, effectiveness (here defined as the chance of a live birth, assuming that if the GGE was not successful, the embryo would not be transferred), cost and availability of alternative treatments/procedures to prevent the genetic disease or provide enhancement (i.e. preimplantation genetic testing (PGT)), respectively. For each treatment characteristic, 2-3 levels were defined to realistically represent GGE and its current alternatives, donor gametes and ICSI with PGT. Twelve vignettes were created by fractional factorial design. A multinominal logit model assessed how much each treatment characteristic affected participants' choices.

MAIN RESULTS AND THE ROLE OF CHANCE

The 1136 respondents (response rate 61%) were representative of the Dutch adult population in several demographics. Respondents were between 18 and 89 years of age. When no alternative treatment/procedure is available, the risk that GGE would cause (other) congenital abnormalities had the largest effect on whether the Dutch public supported allowing GGE (coefficient = -3.07), followed by effectiveness (coefficient = 2.03). Costs (covered by national insurance, coefficient = -1.14), the type of application (disease or enhancement; coefficient = -1.07), and the effect on child well-being (coefficient = 0.97) had similar effects on whether GGE should be allowed. If an alternative treatment/procedure (e.g. PGT) was available, participants were not categorically opposed to GGE, however, they were strongly opposed to using GGE for enhancement (coefficient = -3.37). The general acceptability of GGE was higher than participants' willingness to personally use it (P < 0.001). When participants considered whether they would personally use GGE, the type of application (disease or enhancement) was more important, whereas effectiveness and costs (covered by national insurance) were less important than when they considered whether GGE should be allowed. Participants who were male, younger and had lower incomes were more likely to allow GGE when no alternative treatment/procedure is available.

LIMITATIONS, REASONS FOR CAUTION

Some (e.g. ethnic, religious) minorities were not well represented. To limit complexity, not all characteristics of GGE could be included (e.g. out-of-pocket costs), therefore, the views gathered from the vignettes reflect only the choices presented to the respondents. The non-included characteristics could be connected to and alter the importance of the studied characteristics. This would affect how closely the reported coefficients reflect 'real-life' importance.

WIDER IMPLICATIONS OF THE FINDINGS

This study is the first to quantify the substantial impact of GGE's effectiveness, costs (covered by national insurance), and effect on child well-being on whether the public considered GGE acceptable. In general, the participants were strikingly risk-averse, in that they weighed the risks of GGE more heavily than its benefits. Furthermore, although only a single study in one country, the results suggests that-if sufficiently safe and effective-the public may approve of using GGE (presumably combined with PGT) instead of solely PGT to prevent passing on a disease. The reported public views can serve as input for future consideration of the ethics and governance of GGE.

STUDY FUNDING/COMPETING INTEREST(S)

Young Academy of the Royal Dutch Academy of Sciences (UPS/RB/745), Alliance Grant of the Amsterdam Reproduction and Development Research Institute (2017-170116) and National Institutes of Health Intramural Research Programme. No competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Ethical Challenges of Germline Genetic Enhancement

The new reproductive technologies have opened the door to different processes of germline genetic enhancement by which the characteristics of an individual according to the interests of the agents involved could be selected during its gestation. Although the initiative is apparently oriented towards developing individuals that would excel in society, critical voices raise the concerns about that this approach would generate and need for a reflection on the ethical, social and legal implications of these techniques and their implementation in society. We reviewed the literature about these issues throughout their historical records to date, focusing on the moral arguments and non-clinical aspects that affect the legal and social environment. We have observed various trends of thought with divergent positions (proactive, preventive, and regulatory) as well as a large number of articles that try to reconcile the different approaches. This review illustrates a series of concepts from the ethics and philosophy fields which are frequently used in studies that evaluate the ethical implications of germline genetic enhancement, such as dignity, benefit, autonomy, and identity. In addition, amongst the many unresolved controversies surrounding genetic enhancement, we identify procreative beneficence, genetic disassociation, gender selection, the value of disability, embryo chimerization, and the psychosocial inequality of potentially enhanced individuals as crucial. We also develop possible scenarios for future debate. We consider especially important the definition and specification of three aspects which are essential for the deployment of new reproductive technologies: the moral status of the embryo undergoing enhancement, the legal status of the enhanced individual, and the responsibility of the agents executing the enhancement. Finally, we propose the precautionary principle as a means to navigate ethical uncertainties.

The ethics of clinical applications of germline genome modification: a systematic review of reasons

STUDY QUESTION

What are the reasons for or against the future clinical application of germline genome modification (GGM)?

SUMMARY ANSWER

A total of 169 reasons were identified, including 90 reasons for and 79 reasons against future clinical application of GGM.

WHAT IS KNOWN ALREADY

GGM is still unsafe and insufficiently effective for clinical purposes. However, the progress made using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)- CRISPR-associated system (Cas) has led scientists to expect to overcome the technical hurdles in the foreseeable future. This has invited a debate on the socio-ethical and legal implications and acceptability of clinical applications of GGM. However, an overview of the reasons presented in this debate is missing.

STUDY DESIGN, SIZE, DURATION

MEDLINE was systematically searched for articles published between January 2011 and June 2016. Articles covering reasons for or against clinical application of intentional modification of the nuclear DNA of the germline were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two researchers independently extracted the reported reasons from the articles and grouped them into categories through content analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

The systematic search yielded 1179 articles and 180 articles were included. Most papers were written by professionals in ethics, (science) journalism and biomedical sciences. Overall, 169 reasons were identified, including 90 reasons for, and 79 reasons against future clinical application of GGM. None of the included articles mentioned more than 60/169 reasons. The reasons could be categorized into: (i) quality of life of affected individuals; (ii) safety; (iii) effectiveness; (iv) existence of a clinical need or alternative; (v) costs; (vi) homo sapiens as a species (i.e. relating to effects on our species); (vii) social justice; (viii) potential for misuse; (ix) special interests exercising influence; (x) parental rights and duties; (xi) comparability to acceptable processes; (xii) rights of the unborn child; and (xiii) human life and dignity. Considerations relating to the implementation processes and regulation were reported.

LIMITATIONS, REASONS FOR CAUTION

We cannot ensure completeness as reasons may have been omitted in the reviewed literature and our search was limited to MEDLINE and a 5-year time period.

WIDER IMPLICATIONS OF THE FINDINGS

Besides needing (pre)clinical studies on safety and effectiveness, authors call for a sound pre-implementation process. This overview of reasons may assist a thorough evaluation of the responsible introduction of GGM.

STUDY FUNDING/COMPETING INTEREST(S)

University of Amsterdam, Alliance Grant of the Amsterdam Reproduction and Development Research Institute (I.D.), and Clinical Center, Department of Bioethics, National Institutes of Health Intramural Research Program (S.H.). There are no competing interests.

Reasons for being in favour of or against genome modification: a survey of the Dutch general public

STUDY QUESTION

What are the general public's reasons for being in favour of or against the use of genome modification for five potential applications?

SUMMARY ANSWER

Overall, 43 reasons for being in favour, 45 reasons for being against as well as 26 conditional reasons for the use of genome modification were identified.

WHAT IS KNOWN ALREADY

Various applications of somatic genome modification are progressing towards clinical introduction and several recent studies have reported on germline genome modification. This has incited a debate on ethical and legal implications and acceptability. There is a growing plea to involve the general public earlier on in the developmental process of science and (bio)technology including genome modification.

STUDY DESIGN SIZE DURATION

In April 2016, a cross-sectional survey was launched online among the Dutch general public. A documentary on genome modification on public television and calls in social media invited viewers and non-viewers, respectively, to participate.

PARTICIPANTS/MATERIALS SETTING METHODS

The questionnaire introduced five potential future applications of genome modification: modified wheat for individuals with gluten intolerance; somatic modification for individuals with neuromuscular diseases; germline modification to prevent passing on a neuromuscular disease; germline modification to introduce resistance to HIV; and germline modification to increase intelligence. Participants were asked to indicate whether and why they would make use of genome modification in these scenarios. The reasons mentioned were analysed through content analysis by two researchers independently. The proportion of respondents that was willing to modify was described per scenario and associations with respondent characteristics were analysed.

MAIN RESULTS AND THE ROLE OF CHANCE

The survey was completed by 1013 participants. Forty-three reasons for being in favour, 45 reasons for being against as well as 26 conditional reasons for the use of genome modification were identified. These could be categorized into 14 domains: safety of the individuals concerned; effectiveness; quality of life of the individuals concerned; existence of a clinical need or an alternative; biodiversity and ecosystems; animal homo sapiens (i.e. relating to effects on humans as a species); human life and dignity; trust in regulation; justice; costs; slippery slope; argument of nature; parental rights and duties; and (reproductive) autonomy. Participants' willingness to use genome modification was dependent on the application: most participants would eat modified wheat if gluten intolerant (74%), would use genome modification to cure his/her own neuromuscular disease (85%) and would apply germline modification to prevent passing on this neuromuscular disease (66%). A minority would apply germline modification to introduce resistance to HIV (30%) or increase intelligence (16%). Being young (odds ratio (OR) = 0.98 per year increase), being male (OR = 2.38), and having watched the documentary (OR = 1.82) were associated with being willing to apply genome modification in more scenarios.

LIMITATIONS REASONS FOR CAUTION

Inquiring for reasons through open questions in a survey allowed for a larger sample size and intuitive responses but resulted in less depth than traditional face-to-face interviews. As the survey was disseminated through social media, the sample is not representative of the overall Dutch population, and hence the quantitative results should not be interpreted as such.

WIDER IMPLICATIONS OF THE FINDINGS

Further public consultation and a more in-depth ethical and societal debate on principles and conditions for responsible use of (germline) genome modification is required prior to future clinical introduction.

STUDY FUNDING/COMPETING INTERESTS

Funded by the University of Amsterdam and University Medical Centre Utrecht. No conflict of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

Effects of SCN9A gene modification on Na+ channel and the expression of nerve growth factor in a rat model of diarrhea‑predominant irritable bowel syndrome

The aim of the present study was to identify whether the sodium voltage-gated channel alpha subunit 9 (SCN9A) gene modification is a potential treatment for diarrhea‑predominant irritable bowel syndrome (D‑IBS), via regulating the Na+ channel and the expression of nerve growth factor (NGF). The recombinant adenovirus vector of the SCN9A gene was established, and rat colon cells were isolated for SCN9A gene modification. All subjects were divided into four groups: i) The SCN9A‑modified (D‑IBS rat model implanted with SCN9A‑modified colon cells), ii) negative control (NC; D‑IBS rat model implanted with colon cells without SCN9A gene modification), iii) blank (D‑IBS rat model without any treatment) and iv) normal (normal rats without any treatment). Western blotting and reverse transcription‑quantitative polymerase chain reaction were used to detect the protein and mRNA expression levels of SCN9A, NGF and voltage gated sodium channels (Nav)1.8 and Nav1.9 in rat colon tissues. Compared with the normal group, the rats in the SCN9A, NC and blank groups had significantly elevated mRNA and protein expression levels of NGF, SCN9A, Nav1.8 and Nav1.9. The rats in the SCN9A group demonstrated significantly increased mRNA and protein expression levels of NGF, SCN9A, Nav1.8 and Nav1.9 compared with the NC group and the blank group (all P<0.05). SCN9A gene modification can promote the expression of Nav1.8 and Nav1.9 channels, in addition to NGF which may provide a novel therapeutic basis for treating of D‑IBS.

Paternal age bioethics

Modern genetic sequencing studies have confirmed that the sperm of older men contain a greater number of de novo germline mutations than the sperm of younger men. Although most of these mutations are neutral or of minimal phenotypic impact, a minority of them present a risk to the health of future children. If demographic trends towards later fatherhood continue, this will likely lead to a more children suffering from genetic disorders. A trend of later fatherhood will accelerate the accumulation of paternal-origin de novo mutations in the gene pool, gradually reducing human fitness in the long term. These risks suggest that paternal age is of ethical importance. Children affected by de novo mutations arising from delayed fatherhood can be said to be harmed, in the sense of 'impersonal' harm or 'non-comparative' harm. Various strategies are open at societal and individual levels towards reducing deleterious paternal age effects. Options include health education to promote earlier fatherhood, incentives for young sperm donors and state-supported universal sperm banking. The latter approach would likely be of the greatest benefit and could in principle be implemented immediately. More futuristically, human germline genetic modification offers the potential to repair heritable mutational damage.