Genome Editing in Livestock Species

Goals / Objectives
The breeding of domestic animals has a longstanding and successful history, starting with domestication several thousand years ago. Modern animal breeding strategies, predominantly based on population genetics, artificial insemination (AI) and embryo transfer (ET) technologies have led to significant increases in the performance of domestic animals, and are the basis for regular supply of high quality animal derived food at acceptable prices. However, the current strategy of marker- assisted selection and breeding of animals to introduce novel traits over multiple generations is too pedestrian in responding to unprecedented challenges such as changing climate, global pandemics, reduction in animal production footprints, and the anticipated 33% increase in global population as well as increase demand for animal protein consumption in the next three decades. The goal of our laboratory is to utilize site-specific genome editing technologies as a basis for ¿directed¿ or ¿rational selection¿ of agricultural traits that are monogenic or if polygeneic, well defined and not too complex. These genome editing tools are expected to facilitate targeted modification of individual traits without affecting the overall genetic merit of the animal thereby ushering animal biotechnology into the functional genomics era. Our laboratory envisions these technologies as essential tools in addressing critical priorities for global food security and environmental sustainability. The specific cooperative agreement (SCA) will help develop and implement these technologies for maximum societal benefit.

Project Methods
ARS has a long standing history of success with creating genetically modified animals with conventional as well as somatic cell transfer technology. A UMD collaborator has recently demonstrated success with the newer genome editing technologies [transcription activator like effector nucleases (TALENS) and clustered regularly interspaced short palindromic repasts (CRISPRs)]. It is the intention of this SCA to embrace the newer technologies and through this collaboration bring these newer genome editing technologies (and their higher success rates over conventional technologies) to the ARS. Collaborative work will focus on establishing direct genome editing technology in livestock and avian species to improve: 1) animal health by introducing resistance diseases significant economic impact to enhance growth, minimize zoonoses (in the case of zoonotic diseases) and reduce the need for antibiotics to minimize the development of antibiotic resistance and antibiotic residue in food products, and 2) biosynthetic pathway. a. CRISPR enzyme complexes are capable of gene-specific modifications of the genome and will be utilized to address selected phenotypes. b. In vivo-derived embryos will be collected and UMD-CP and ARS scientists will use CRISPRs for site-directed mutagenesis or the introduction of double strand breaks to induce small deletions of a target gene(s) in the genome of livestock embryos with the purpose of ablating the target gene function as a means to either test for gene function or generate new desirable phenotypes. c. UMD and ARS scientists, after manipulation of embryos with CRISPR, will transfer the embryos to recipient females to generate target-gene-deficient offspring and the resultant progeny will be screened for gene silencing and the predicted phenotype. d. The animals will be housed and reared in ARS facilities. e. The genes to be addressed under this agreement are associated with both a proof of concept for the use of the technology in cattle and swine, and to address metabolic and zoonotic disease. Projects include, disease/antibiotic resistance and improved growth via expression of an essential amino acid biosynthetic pathway in order to minimize feed additives.