Genetically modified organisms: adapting regulatory frameworks for evolving genome editing technologies

Genetic modification of living organisms has been a prosperous activity for research and development of agricultural, industrial and biomedical applications. Three decades have passed since the first genetically modified products, obtained by transgenesis, become available to the market. The regulatory frameworks across the world have not been able to keep up to date with new technologies, monitoring and safety concerns. New genome editing techniques are opening new avenues to genetic modification development and uses, putting pressure on these frameworks. Here we discuss the implications of definitions of living/genetically modified organisms, the evolving genome editing tools to obtain them and how the regulatory frameworks around the world have taken these technologies into account, with a focus on agricultural crops. Finally, we expand this review beyond commercial crops to address living modified organism uses in food industry, biomedical applications and climate change-oriented solutions.

CRISPR-mediated base editing in mice using cytosine deaminase base editor 4

BACKGROUND: Many human genetic diseases arise from point mutations. These genetic diseases can theoretically be corrected through gene therapy. However, gene therapy in clinical application is still far from mature. Nearly half of the pathogenic single-nucleotide polymorphisms (SNPs) are caused by G:C>A:T or T:A>C:G base changes and the ideal approaches to correct these mutations are base editing. These CRISPR-Cas9-mediated base editing does not leave any footprint in genome and does not require donor DNA sequences for homologous recombination. These base editing methods have been successfully applied to cultured mammalian cells with high precision and efficiency, but BE4 has not been confirmed in mice. Animal models are important for dissecting pathogenic mechanism of human genetic diseases and testing of base correction efficacy in vivo. Cytidine base editor BE4 is a newly developed version of cytidine base editing system that converts cytidine (C) to uridine (U). RESULTS: In this study, BE4 system was tested in cells to inactivate GFP gene and in mice to introduce single-base substitution that would lead to a stop codon in tyrosinase gene. High percentage albino coat-colored mice were obtained from black coat-colored donor zygotes after pronuclei microinjection. Sequencing results showed that expected base changes were obtained with high precision and efficiency (56.25%). There are no off-targeting events identified in predicted potential off-target sites. CONCLUSIONS: Results confirm BE4 system can work in vivo with high precision and efficacy, and has great potentials in clinic to repair human genetic mutations.

Tratamiento farmacológico y génico en las distrofias musculares de Duchenne y Becker / Pharmacologic and genetic treatment in the Duchenne and Becker muscular dystrophies

Introducción: Las distrofias musculares son las enfermedades degenerativas más comunes dentro de las enfermedades neuromusculares, cursan con debilidad muscular que progresa hasta la pérdida de la deambulación y en la segunda década de vida surgen complicaciones cardíacas, respiratorias y ortopédicas. Objetivo: Analizar el estado actual de los tratamientos génico y farmacológico en las distrofias musculares de Duchenne y Becker Métodos: Se realizó una búsqueda en los meses de enero, febrero y marzo de 2018 en las bases de datos Medline, Cinhal, Web Of Science y Scopus. Se obtuvieron 232 resultados y después de aplicar los criterios de inclusión y exclusión, se consiguieron para analizar 15 artículos válidos para la revisión. Resultados: Los artículos analizados investigan mayoritariamente el efecto de las terapias mencionadas a nivel de funcionalidad y de síntesis de la proteína distrofina durante períodos largos, en los que participan muestras de tamaño y edades variadas tanto como distrofia muscular de Duchenne y como distrofia muscular de Becker. Conclusiones: Existen más artículos enfocados en la distrofia muscular de Duchenne que en la distrofia muscular de Becker. Esto puede ser debido a que la primera es la más grave y de peor pronóstico. Sigue siendo necesario realizar más estudios para avanzar sobre el estado actual de estos tratamientos(AU)

Introduction: Muscular dystrophies are one of the most common degenerative pathologies within neuromuscular diseases. They present muscular weakness that develops until loss of wandering and in the second decade of life can appear cardiac, respiratory and orthopaedic complications. Objective: To know the current state of genetic and pharmacology treatments in the Duchenne and Becker muscular dystrophies. Methods: A search was made from January to March 2018 at Medline, Cinhal, Web Of Science and Scopus databases. 232 results were obtained, and applying the inclusion and exclusion criteria, 15 acceptable articles for reviewing were found. Results: Analyzed articles mostly investigate the effect of the mentioned therapies in the levels of functionality and dystrophin protein synthesis during long periods, in which samples of different sizes and ages are used. Conclusions: There are more articles focused on Duchenne Muscular Dystrophy than Becker Muscular Dystrophy. That can be due to the fact that the first is the most severe and with the worst prognosis. It is still necessary to carry out more scientific studies to move forward from the current stage of these treatments(AU)

Gene therapy: advances, challenges and perspectives / Terapia gênica: avanços, desafios e perspectivas

ABSTRACT The ability to make site-specific modifications to the human genome has been an objective in medicine since the recognition of the gene as the basic unit of heredity. Thus, gene therapy is understood as the ability of genetic improvement through the correction of altered (mutated) genes or site-specific modifications that target therapeutic treatment. This therapy became possible through the advances of genetics and bioengineering that enabled manipulating vectors for delivery of extrachromosomal material to target cells. One of the main focuses of this technique is the optimization of delivery vehicles (vectors) that are mostly plasmids, nanostructured or viruses. The viruses are more often investigated due to their excellence of invading cells and inserting their genetic material. However, there is great concern regarding exacerbated immune responses and genome manipulation, especially in germ line cells. In vivo studies in in somatic cell showed satisfactory results with approved protocols in clinical trials. These trials have been conducted in the United States, Europe, Australia and China. Recent biotechnological advances, such as induced pluripotent stem cells in patients with liver diseases, chimeric antigen receptor T-cell immunotherapy, and genomic editing by CRISPR/Cas9, are addressed in this review.

RESUMO A habilidade de fazer modificações pontuais no genoma humano tem sido o objetivo da medicina desde o conhecimento do DNA como unidade básica da hereditariedade. Entende-se terapia gênica como a capacidade do melhoramento genético por meio da correção de genes alterados (mutados) ou modificações sítio-específicas, que tenham como alvo o tratamento terapêutico. Este tipo de procedimento tornou-se possível por conta dos avanços da genética e da bioengenharia, que permitiram a manipulação de vetores para a entrega do material extracromossomal em células-alvo. Um dos principais focos desta técnica é a otimização dos veículos de entrega (vetores) que, em sua maioria, são plasmídeos, nanoestruturados ou vírus − sendo estes últimos os mais estudados, devido à sua excelência em invadir as células e inserir seu material genético. No entanto, existe grande preocupação referente às respostas imunes exacerbadas e à manipulação do genoma, principalmente em linhagens germinativas. Estudos em células somáticas in vivo apresentaram resultados satisfatórios, e já existem protocolos aprovados para uso clínico. Os principais trials têm sido conduzidos nos Estados Unidos, Europa, Austrália e China. Recentes avanços biotecnológicos empregados para o aprimoramento da terapia gênica, como células-tronco pluripotentes induzidas em pacientes portadores de doenças hepáticas, imunoterapia com células T do receptor do antígeno quimera e edição genômica pelos sistema CRISPR/Cas9, são abordados nesta revisão.