CRISPR in livestock: From editing to printing

Abstract

Precise genome editing of large animals applied to livestock and biomedicine is nowadays possible since the CRISPR revolution. This review summarizes the latest advances and the main technical issues that determine the success of this technology. The pathway from editing to printing, from engineering the genome to achieving the desired animals, does not always imply an easy, fast and safe journey. When applied in large animals, CRISPR involves time- and cost-consuming projects, and it is mandatory not only to choose the best approach for genome editing, but also for embryo production, zygote microinjection or electroporation, cryopreservation and embryo transfer. The main technical refinements and most frequent questions to improve this disruptive biotechnology in large animals are presented. In addition, we discuss some CRISPR applications to enhance livestock production in the context of a growing global demand of food, in terms of increasing efficiency, reducing the impact of farming on the environment, enhancing pest control, animal welfare and health. The challenge is no longer technical. Controversies and consensus, opportunities and threats, benefits and risks, ethics and science should be reconsidered to enter into the CRISPR era.

Keywords: Cows; Gene editing; Goats; Pigs; Sheep.

Fig. 1

The CRISPR pipeline to transform livestock: From editing to printing. Different approaches for CRISPR-Cas system, consisting of a single guide RNA (sgRNA) designed to direct Cas9 to the desired DNA site and induce double strand breaks (DSB). DNA cleavage results in different gene repair mechanisms as nonhomologous end joining (NHEJ) or homology-directed repair (HDR, i.e., in the presence of a DNA donor template). Zygotes are obtained by in vitro embryo production (in vitro maturation and fertilization), or derived from in vivo production (insemination and oviduct flushing). Delivery of CRISPR-Cas components into the zygote is performed by direct microinjection into the cytoplasm, or alternatively, by electroporation with no need for embryo micromanipulation. Embryo transfer is carried out either with fresh or cryopreserved embryos by vitrification with minimum volume method (e.g., Cryotop). The wide range of CRISPR applications in large animals include improving productive traits, enhancing animal welfare through adaptation and resilience, conferring resistance to infectious and transmissible diseases, generating animal models for biomedical research, and suppressing other species considered as pests for livestock.