Genome engineering through CRISPR/Cas9 technology in the human germline and pluripotent stem cells

With the recent development of CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 genome editing technology, the possibility to genetically manipulate the human germline (gametes and embryos) has become a distinct technical possibility. Although many technical challenges still need to be overcome in order to achieve adequate efficiency and precision of the technology in human embryos, the path leading to genome editing has never been simpler, more affordable, and widespread. In this narrative review we seek to understand the possible impact of CRISR/Cas9 technology on human reproduction from the technical and ethical point of view, and suggest a course of action for the scientific community. This non-systematic review was carried out using Medline articles in English, as well as technical documents from the Human Fertilisation and Embryology Authority and reports in the media. The technical possibilities of the CRISPR/Cas9 technology with regard to human reproduction are analysed based on results obtained in model systems such as large animals and laboratory rodents. Further, the possibility of CRISPR/Cas9 use in the context of human reproduction, to modify embryos, germline cells, and pluripotent stem cells is reviewed based on the authors' expert opinion. Finally, the possible uses and consequences of CRISPR/cas9 gene editing in reproduction are analysed from the ethical point of view. We identify critical technical and ethical issues that should deter from employing CRISPR/Cas9 based technologies in human reproduction until they are clarified. Overcoming the numerous technical limitations currently associated with CRISPR/Cas9 mediated editing of the human germline will depend on intensive research that needs to be transparent and widely disseminated. Rather than a call to a generalized moratorium, or banning, of this type of research, efforts should be placed on establishing an open, international, collaborative and regulated research framework. Equally important, a societal discussion on the risks, benefits, and preferred applications of the new technology, including all relevant stakeholders, is urgently needed and should be promoted, and ultimately guide research priorities in this area.