The technical risks of human gene editing

Efficient CRISPR genome editing and integrative genomic analyses reveal the mosaicism of Cas-induced mutations and pleiotropic effects of scarlet gene in an emerging model system

Despite the revolutionary impacts of CRISPR-Cas gene editing systems, the effective and widespread use of CRISPR technologies in emerging model organisms still faces significant challenges. These include the inefficiency in generating heritable mutations at the organismal level, limited knowledge about the genomic consequences of gene editing, and an inadequate understanding of the inheritance patterns of CRISPR-Cas-induced mutations. This study addresses these issues by 1) developing an efficient microinjection delivery method for CRISPR editing in the microcrustacean Daphnia pulex; 2) assessing the editing efficiency of Cas9 and Cas12a nucleases, examining mutation inheritance patterns, and analyzing the local and global mutation spectrum in the scarlet mutants; and 3) investigating the transcriptomes of scarlet mutants to understand the pleiotropic effects of scarlet underlying their swimming behavior changes. Our reengineered CRISPR microinjection method results in efficient biallelic editing with both nucleases. While indels are dominant in Cas-induced mutations, a few on-site large deletions (>1kb) are observed, most likely caused by microhomology-mediated end joining repair. Knock-in of a stop codon cassette to the scarlet locus was successful, despite complex induced mutations surrounding the target site. Moreover, extensive germline mosaicism exists in some mutants, which unexpectedly produce different phenotypes/genotypes in their asexual progenies. Lastly, our transcriptomic analyses unveil significant gene expression changes associated with scarlet knock-out and altered swimming behavior in mutants, including several genes (e.g., NMDA1, ABAT, CNTNAP2) involved in human neurodegenerative diseases. This study expands our understanding of the dynamics of gene editing in the tractable model organism Daphnia and highlights its promising potential as a neurological disease model.

Advancements and future prospects of adeno-associated virus-mediated gene therapy for sensorineural hearing loss

Sensorineural hearing loss (SNHL), a highly prevalent sensory impairment, results from a multifaceted interaction of genetic and environmental factors. As we continually gain insights into the molecular basis of auditory development and the growing compendium of deafness genes identified, research on gene therapy for SNHL has significantly deepened. Adeno-associated virus (AAV), considered a relatively secure vector for gene therapy in clinical trials, can deliver various transgenes based on gene therapy strategies such as gene replacement, gene silencing, gene editing, or gene addition to alleviate diverse types of SNHL. This review delved into the preclinical advances in AAV-based gene therapy for SNHL, spanning hereditary and acquired types. Particular focus is placed on the dual-AAV construction method and its application, the vector delivery route of mouse inner ear models (local, systemic, fetal, and cerebrospinal fluid administration), and the significant considerations in transforming from AAV-based animal model inner ear gene therapy to clinical implementation.

Islamic Perspectives on Polygenic Testing and Selection of IVF Embryos (PGT-P) for Optimal Intelligence and Other Non-Disease-Related Socially Desirable Traits

In recent years, the genetic testing and selection of IVF embryos, known as preimplantation genetic testing (PGT), has gained much traction in clinical assisted reproduction for preventing transmission of genetic defects. However, a more recent ethically and morally controversial development in PGT is its possible use in selecting IVF embryos for optimal intelligence quotient (IQ) and other non-disease-related socially desirable traits, such as tallness, fair complexion, athletic ability, and eye and hair colour, based on polygenic risk scores (PRS), in what is referred to as PGT-P. Artificial intelligence (AI) and machine learning-based analysis of big data sets collated from genome sequencing of specific human ethnic populations can be used to estimate an individual embryo's likelihood of developing such multifactorial traits by analysing the combination of specific genetic variants within its genome. Superficially, this technique appears compliant with Islamic principles and ethics. Because there is no modification of the human genome, there is no tampering with Allah's creation (taghyīr khalq Allah). Nevertheless, a more critical analysis based on the five maxims of Islamic jurisprudence (qawa'id fiqhiyyah) that are often utilized in discourses on Islamic bioethics, namely qaṣd (intention), yaqın̄ (certainty), ḍarar (injury), ḍarūra (necessity), and `urf (custom), would instead reveal some major ethical and moral flaws of this new medical technology in the selection of non-disease-related socially desirable traits, and its non-compliance with the spirit and essence of Islamic law (shariah). Muslim scholars, jurists, doctors, and biomedical scientists should debate this further and issue a fatwa on this new medical technology platform.

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.

Revertant Mosaicism in Genodermatoses: Natural Gene Therapy Right before Your Eyes

Revertant mosaicism (RM) is the intriguing phenomenon in which nature itself has successfully done what medical science is so eagerly trying to achieve: correcting the effect of disease-causing germline variants and thereby reversing the disease phenotype back to normal. RM was molecularly confirmed for the first time in a genodermatosis in 1997, the genetic skin condition junctional epidermolysis bullosa (EB). At that time, RM was considered an extraordinary phenomenon. However, several important discoveries have changed this conception in the past few decades. First, RM has now been identified in all major subtypes of EB. Second, RM has also been identified in many other genodermatoses. Third, a theoretical mathematical exercise concluded that reverse mutations should be expected in all patients with a recessive subtype of EB or any other genodermatosis. This has shifted the paradigm from RM being an extraordinary phenomenon to it being something that every physician working in the field of genodermatoses should be looking for in every patient. It has also raised hope for new treatment options in patients with genodermatoses. In this review, we summarize the current knowledge on RM and discuss the perspectives of RM for the future treatment of patients with genodermatoses.

Application of CRISPR/Cas Genomic Editing Tools for HIV Therapy: Toward Precise Modifications and Multilevel Protection

Although highly active antiretroviral therapy (HAART) can robustly control human immunodeficiency virus (HIV) infection, the existence of latent HIV in a form of proviral DNA integrated into the host genome makes the virus insensitive to HAART. This requires patients to adhere to HAART for a lifetime, often leading to drug toxicity or viral resistance to therapy. Current genome-editing technologies offer different strategies to reduce the latent HIV reservoir in the body. In this review, we systematize the research on CRISPR/Cas-based anti-HIV therapeutic methods, discuss problems related to viral escape and gene editing, and try to focus on the technologies that effectively and precisely introduce genetic modifications and confer strong resistance to HIV infection. Particularly, knock-in (KI) approaches, such as mature B cells engineered to produce broadly neutralizing antibodies, T cells expressing fusion inhibitory peptides in the context of inactivated viral coreceptors, or provirus excision using base editors, look very promising. Current and future advancements in the precision of CRISPR/Cas editing and its delivery will help extend its applicability to clinical HIV therapy.

Genome Editing among Bioethics and Regulatory Practices

In the last decade, genome editing technologies became very effective and several clinical trials have been started in order to use them for treating some genetic diseases. Interestingly, despite more than 50 years of discussion about the frontiers of genetics in human health and evolution, the debate about the bioethics and the regulatory practices of genome editing is still far from satisfactory answers. This delay results from an excessive emphasis on the effectiveness of the genome editing technologies that is relevant for the regulatory practices, but not at a bioethical level. Indeed, other factors (such as accessibility and acceptability) could make these techniques not accepted at the bioethical level, even in the presence of their 100% effectiveness.

You can't keep a bad idea down: Dark history, death, and potential rebirth of eugenics

"Be careful what you wish for": This adage guides both how this project came to life, and how the topic covered in this review continues to unfold. What began as talks between two friends on shared interests in military history led to a 4-year discussion about how our science curriculum does little to introduce our students to societal and ethical impacts of the science they are taught. What emerged was a curricular idea centered on how "good intentions" of some were developed and twisted by others to result in disastrous consequences of state-sanctioned eugenics. In this article, we take the reader (as we did our students) through the long and soiled history of eugenic thought, from its genesis to the present. Though our focus is on European and American eugenics, we will show how the interfaces and interactions between science and society have evolved over time but have remained ever constant. Four critical 'case studies' will also be employed here for deep, thoughtful exploration on a particular eugenic issue. The goal of the review, as it is with our course, is not to paint humanity with a single evil brush. Instead, our ambition is to introduce our students/readers to the potential for harm through the misapplication and misappropriation of science and scientific technology, and to provide them with the tools to ask the appropriate questions of their scientists, physicians, and politicians.

Cutting Through the "Gray Area": An Analysis of the IBC Regulatory Oversight of Applications of CRISPR Technology in Clinical Research

The advent of clustered regularly interspaced short palindromic repeats (CRISPR) technology has quickly ushered in a new era of gene editing and offered exciting potential for the development of biomedical products. While the breadth of applications for CRISPR encompasses nearly the entire field of medical science, its utilization to produce next-generation CAR T cells stands to benefit most substantially in the short-term. These novel therapeutics are now beginning to enter the clinical trial phase of the numerous approval pipelines, but does the existing regulatory framework have the capability to adequately review and approve the initiation of these new age research endeavors in the clinical setting? This analysis will illuminate the similarity and differences between CRISPR developed interventions and existing techniques used to produce biomedical products from a regulatory perspective in the United States. Further, the "gray area" surrounding CRISPR regulatory oversight will be explored and recommendations will be made to facilitate the elimination of inconsistencies that currently exist in the assessment of this work prior to the initiation of associated clinical trials.

Advanced Therapies and Regulatory Framework in Different Areas of the Globe: Past, Present, and Future

PURPOSE

The field of human medicine is in a constant state of evolution, developing and incorporating technological advances from diverse scientific fields. In recent years, cellular and gene therapies have come of age, challenging regulatory agencies to define the path for commercial registration. Approval necessarily demands robust evidence for safety and efficacy, but these exigencies must not be such that they render unviable the development and testing of the therapeutic agent. Furthermore, reimbursement strategies are required to guarantee commercial viability of these products, to avoid the risk that they will be removed from the market or become unavailable to most patients through lack of financial resources. To address such challenges, several countries have created strategies to manage advanced therapy products.

METHODS

Based on official documents published by regulatory agencies worldwide, this review summarizes the current scenario in the United States, Europe, Brazil, Japan, South Korea, and China in this regard, discussing the harmonized and dissonant aspects of the regulatory framework in different regions of the world and exploring perspectives for the future.

FINDINGS

The technical aspects of advanced therapies are increasingly complex, bringing challenges for high mass commercialization and demanding specific regulation. The regulatory framework of the analyzed regions is mainly recent and discordant, but many harmonizing initiatives were observed.

IMPLICATIONS

The comparative analysis of regulatory frameworks in different parts of the world is informative, as scientists must be aware of the rationale of regulators to assertively develop new technology and products that will be commercialized. The comparative analysis also provides insight into the main dissonances that must be addressed, fostering the harmonization of local regulatory frameworks. Many unanswered questions still lie ahead for the field of advanced therapies, and empirical evidence will be the most effective way to separate hype from hope and to establish the most sustainable mechanisms to regulate and finance such products in each part of the world.

Advances and challenges in adeno-associated viral inner-ear gene therapy for sensorineural hearing loss

There is growing attention and effort focused on treating the root cause of sensorineural hearing loss rather than managing associated secondary characteristic features. With recent substantial advances in understanding sensorineural hearing-loss mechanisms, gene delivery has emerged as a promising strategy for the biological treatment of hearing loss associated with genetic dysfunction. There are several successful and promising proof-of-principle examples of transgene deliveries in animal models; however, there remains substantial further progress to be made in these avenues before realizing their clinical application in humans. Herein, we review different aspects of development, ongoing preclinical studies, and challenges to the clinical transition of transgene delivery of the inner ear toward the restoration of lost auditory and vestibular function.

Responsible Translational Pathways for Germline Gene Editing?

PURPOSE OF REVIEW

Continued development of gene editing techniques has raised the real possibility of clinical application of germline gene editing. These results, as well as reports of an unethical experiment which resulted in the birth of at least two children from edited embryos in 2018, have highlighted the urgency and importance of ethical issues about translational pathways for editing of human germline cells. Charting responsible translational pathways for germline gene editing requires tackling some significant and complex ethical issues.

RECENT FINDINGS

A literature on development of clinical applications of germline gene editing is emerging, and several key ethical issues are coming into focus as major challenges for responsible translational pathways.

SUMMARY

Potential clinical utility, clinical justification, and human subjects research for germline gene editing raise outstanding ethical questions. Work on these questions will help provide guidance to researchers and clinicians and direct translational projects toward justifiable applications.