Genetics: deaf by design

A burden shared: The evolutionary case for studying human deafness in Drosophila

Hearing impairment is the most prevalent sensory disease in humans and can have dramatic effects on the development, and preservation, of our cognitive abilities and social interactions. Currently 20 % of the world's population suffer from a form of hearing impairment; this is predicted to rise to 25 % by 2050. Despite this staggering disease load, and the vast damage it inflicts on the social, medical and economic fabric of humankind, our ability to predict, or prevent, the loss of hearing is very poor indeed. We here make the case for a paradigm shift in our approach to studying deafness. By exploiting more forcefully the molecular-genetic conservation between human hearing and hearing in morphologically distinct models, such as the fruit fly Drosophila melanogaster, we believe, a deeper understanding of hearing and deafness can be achieved. An understanding that moves beyond the surface of the 'deafness genes' to probe the underlying bedrock of hearing, which is shared across taxa, and partly shared across modalities. When it comes to understanding the workings (and failings) of human sensory function, a simple fruit fly has a lot to offer and a fly eye might sometimes be a powerful model for a human ear. Particularly the use of fly avatars, in which specific molecular (genetic or proteomic) states of humans (e.g. specific patients) are experimentally reproduced, in order to study the corresponding molecular mechanisms (e.g. specific diseases) in a controlled yet naturalistic environment, is a tool that promises multiple unprecedented insights. The use of the fly - and fly avatars - would benefit humans and will help enhance the power of other scientific models, such as the mouse.

Transfer of embryos with positive PGT-M results: Genetic Counselors' perspectives and ethical considerations

Increasing numbers of fertility patients use preimplantation genetic testing for monogenic conditions (PGT-M) during in vitro fertilization (IVF). While PGT-M is primarily used to avoid implanting embryos with a monogenic condition, patients can request to transfer an embryo with the monogenic condition (positive embryo transfer), especially in cases where an IVF cycle results in no unaffected embryos. Transferring embryos with known disease-causing variants raises ethical concerns. There is limited understanding about how stakeholders in the assisted reproductive technology (ART) field approach these issues. In this study, genetic counselors were sent a survey to gather insight into their views about transferring embryos with different monogenic conditions. N = 99 genetic counselors completed the survey, 22 of whom had experience with patients requesting or deciding to transfer an embryo with a monogenic condition (positive embryo transfer experience). Most participants, including those with positive embryo transfer experience, were supportive of positive embryo transfer, regardless of the genetic condition. While participating genetic counselors were largely supportive of all patient decisions, they reported increased moral uneasiness around transferring embryos with life-limiting monogenic conditions, such as Huntington's disease. Further investigation into the experiences of genetic counselors who have experienced positive embryo transfer requests in practice can help delineate the ethical questions that ART providers face in this context and clarify how genetic counselors can contribute to establishing guidelines in the ART field.

A New Ethical Framework for Assessing the Unique Challenges of Fetal Therapy Trials

New fetal therapies offer important prospects for improving health. However, having to consider both the fetus and the pregnant woman makes the risk-benefit analysis of fetal therapy trials challenging. Regulatory guidance is limited, and proposed ethical frameworks are overly restrictive or permissive. We propose a new ethical framework for fetal therapy research. First, we argue that considering only biomedical benefits fails to capture all relevant interests. Thus, we endorse expanding the considered benefits to include evidence-based psychosocial effects of fetal therapies. Second, we reject the commonly proposed categorical risk and/or benefit thresholds for assessing fetal therapy research (e.g., only for life-threatening conditions). Instead, we propose that the individual risks for the pregnant woman and the fetus should be justified by the benefits for them and the study's social value. Studies that meet this overall proportionality criterion but have mildly unfavorable risk-benefit ratios for pregnant women and/or fetuses may be acceptable.

Assessing potential cures: are there distinctive elements of value beyond health gain?

Assessing the 'value' of potential cures can be challenging, as some have suggested that cures may offer distinctive benefits from noncurative treatments. We explore what these - previously unspecified - additional benefits may be. We suggest that three new elements of value seem distinctive to cures: liberation from the identity of being diseased, liberation from the stigma associated with the disease and liberation from the burden of ongoing therapy. However, including additional elements of value in health technology assessment may result in double counting and requires consideration of potential opportunity costs. We suggest health technology assessment should explore the relevance of these three elements of value and may have good reasons to - judiciously - integrate them through the deliberative process.

The Past, Present, and Future of Preimplantation Genetic Testing

Preimplantation genetic testing (PGT) of oocytes and embryos is the earliest form of prenatal testing. PGT requires in vitro fertilization for embryo creation. In the past 25 years, the use of PGT has increased dramatically. The indications of PGT include identification of embryos harboring single-gene disorders, chromosomal structural abnormalities, chromosomal numeric abnormalities, and mitochondrial disorders; gender selection; and identifying unaffected, HLA-matched embryos to permit the creation of a savior sibling. PGT is not without risks, limitations, or ethical controversies. This review discusses the techniques and clinical applications of different forms of PGT and the debate surrounding its associated uncertainty and expanded use.

Preimplantation genetic testing: indications and controversies

In the last two decades, the use of preimplantation genetic testing has increased dramatically. This testing is used for identifying singlegene disorders, chromosomal abnormalities, mitochondrial disorders, gender selection in non-mendelian disorders with unequal gender distribution, aneuploidy screening, and other preconceptually identified genetic abnormalities in prospective parents. Genetic testing strategies and diagnostic accuracy continues to improve, but not without risks or controversies. In this review the authors discuss the techniques and clinical application of preimplantation genetic diagnosis, and the debate surrounding its associated uncertainty and expanded use.

Analysing our qualms about "designing" future persons: autonomy, freedom of choice, and interfering with nature

Actually possible and conceivable future uses of preimplantation genetic diagnosis (PGD) and germ-line genetic intervention in assisted reproduction seem to offer increasing possibilities of choosing the kind of persons that will be brought to existence. Many are troubled by the idea of these technologies being used for enhancement purposes. How can we make sense of this worry? Why are our thoughts about therapeutic genetic interventions and non-genetic enhancement (for instance education) not accompanied by the same intuitive uneasiness? I argue that the concepts of autonomy and freedom of choice, typically invoked to delimit the morally acceptable uses of reproductive technologies, cannot fully answer these questions. Instead, I suggest that an alternative answer might begin with reflections on the notion of interfering with nature. Drawing on Martin Heidegger's critique of modern technology and Hans Jonas's moral philosophy, I outline an argument that attempts to capture what might be particularly troubling about the idea of "designing" future persons. At the core of the argument is the suggestion that enhancing selections and modifications on embryos might be bound up with an instrumentalising, non-responsive perspective on the future persons into which they are intended to grow.

Assessing parental attitudes toward genetic testing for childhood hearing loss: Before and after genetic consultation

We report on the development of a Genetic Attitude Assessment Tool (GAAT) to measure parental attitudes in contemplating genetic testing for childhood hearing loss, and to examine the differences in assessments made before and after genetic counseling. The GAAT tool was administered to a convenient sample of 119 parents of children with bilateral sensorineural hearing loss. The respondents completed the survey either before (n = 77) or after (n = 42) genetic counseling. Exploratory Factor Analysis was applied to identify and quantify the underlying psychosocial structure. Our results showed the validated 54-item GAAT instrument contains six subscales: (1) "test intention," (2) "beliefs in non-genetic causes of hearing loss," (3) "deferral of decision to undergo genetic testing," (4) "appropriate use of genetic testing results," (5) "beliefs in the benefits," and (6) "concerns about stigma." The respondents who answered the survey after genetic counseling had higher "test intention" (P = 0.017) and endorsed to a greater extent "beliefs in the benefits" (P < 0.001). They believed to a lesser extent that childhood hearing loss was due to "non-genetic causes" (P < 0.001) and were less inclined to prefer "decision deferral" (P = 0.031). Respondents who themselves had a hearing loss expressed a significantly weaker belief in "non-genetic causes" of hearing loss (P < 0.0001). In conclusion the validated GAAT instrument is responsive to changes in parental attitudes after genetic counseling. The GAAT may be used to monitor parental attitudes serially, to further understand how parental attitudes change from pre genetic counseling, post genetic counseling, to post test result disclosure.

Parental narratives on genetic testing for children with hearing loss: A qualitative inquiry

Studies on parental attitudes towards genetic testing for hearing loss have surveyed parents of newborns with hearing loss as well as deaf and hearing adults. Although research indicates that most people have positive attitudes about genetic testing, few studies examine parental narratives about the personal implications of genetic hearing loss in their children. In this qualitative study we conducted semi-structured interviews with 24 parents whose children had been referred for, but had not yet undergone, genetic testing for hearing loss. The parents were recruited to represent a diverse range of racial, ethnic, and socioeconomic groups. Genetics and genetic testing for hearing loss were poorly understood topics. Beyond supporting or opposing genetic testing for hearing loss, parents' construction of meaning included struggles to locate responsibility (metaphysical attributions, ascription or alleviation of parental responsibility) as well as questions about the usefulness and implications of genetic testing for hearing loss in their child. Based on the themes that emerged from this study, we highlight the need for healthcare professionals to be aware and sensitized to parents' narratives, personal meanings and socio-cultural context when referring them for genetic testing for hearing loss. Listening attentively to parental narratives can help minimize prevailing misconceptions among parents and enable appropriate medical care and education.

Genetic screening and diagnosis

PURPOSE OF REVIEW

To review the latest developments in screening and diagnosis of non-chromosomal genetic diseases.

RECENT FINDINGS

Major recent advances include the completion of the Human Genome Project, the use of microarray and related technologies for mass screening and diagnosis of thousands of genetic abnormalities, and non-invasive prenatal diagnosis using fetal DNA in maternal plasma.

SUMMARY

The rapid development in molecular biological technologies makes it possible to screen and to diagnosis thousands of genetic conditions, mutations and also predispositions to chronic diseases or traits, either prenatally or after birth. Clinical application of non-invasive prenatal diagnosis using fetal DNA in maternal plasma has become a reality. The arrival of the molecular genetic era also leads to many new ethical, social and medico-legal problems and dilemmas that obstetricians will have to face in the near future. There is an urgent need for the development of a new model for provision of genetic screening and diagnosis.

Ethics and the future of preimplantation genetic diagnosis

The future growth of preimplantation genetic diagnosis (PGD) will depend on refinements in genetic knowledge and genetic analysis of blastomeres. Equally important, however, is an acceptance of the ethical legitimacy of parents using technologies to select genetic traits of offspring. Objections based on embryo status, the giftedness of reproduction, eugenics, and protecting the child's welfare are not convincing grounds to oppose most uses of PGD. Whether PGD should be accepted for new medical or non-medical uses should depend upon a careful assessment of the proposed use's importance to the person or couple requesting it, and the harmful effects, if any, which it might cause. Such an approach leads to the conclusion that most new medical uses of PGD and some non-medical uses should be permitted.