The transformational impact of site-specific DNA modifiers on biomedicine and agriculture.

Kathryn Polkoff,Jorge A Piedrahita

doi:10.21451/1984-3143-ar2018-0065

Kathryn Polkoff, Jorge A Piedrahita

Open Access

https://doi.org/10.21451/1984-3143-ar2018-0065

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Journal: Animal reproduction	Publication Date: Jan 1, 2018
Citations: 1	License type: cc-by

Affiliation: North Carolina State University

Abstract

The development of genetically modified livestock has been dependent on incremental technological advances such as embryo transfer, homologous recombination, and somatic cell nuclear transfer (SCNT). This development rate has increased exponentially with the advent of targeted gene modifiers such as zinc finger nucleases, TAL-effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR-Cas). CRISPR-Cas based systems in particular have broad applicability, and have low technical and economic barriers for their implementation. As a result, they are having, and will continue to have, a transformational impact in the field of gene editing in domestic animals. With these advances also comes the responsibility to properly apply this technology so it has a beneficial effect throughout all levels of society.

Highlights

Embryo culture and embryo transfer, pronuclear injection, homologous recombination: technical advances that gradually made it possible to generate genetically modified large animals such as pigs, cattle and sheep
From the initial observation of Keith Campbell and Ian Wilmut that sheep could be cloned from a somatic cell using somatic cell nuclear transfer (SCNT) (Campbell et al, 1996), multiple groups rapidly moved to genetic modification of somatic cells in vitro followed by SCNT
While homology-directed repair (HDR) and non-homologous end joining (NHEJ) are effective for knockouts and knock-ins, the advent of base editors introduces a new paradigm for therapeutic gene editing

Summary

Introduction

Embryo culture and embryo transfer, pronuclear injection, homologous recombination: technical advances that gradually made it possible to generate genetically modified large animals such as pigs, cattle and sheep. From the initial observation of Keith Campbell and Ian Wilmut that sheep could be cloned from a somatic cell using SCNT (Campbell et al, 1996), multiple groups rapidly moved to genetic modification of somatic cells in vitro followed by SCNT This led to the first reports of SCNT-generated transgenic sheep (Schnieke et al, 1997), pigs (Dai et al, 2002) and cattle (Cibelli et al, 1998). There was tremendous excitement in the field and most, if not all, laboratories worldwide working in the area of genetic modification of domestic animals quickly moved to implement SCNT While this transition was successful for many groups, gene targeting by HR remained a significant barrier. Homologous Recombination (HR) Homologous recombination and Smithies, 2001; Smithies et al, 1984; targeted NHEJ

Short or no homology arms

Single and multi loci targeted epigenetic modifications

Base editors

Approaches to generating gene edited offspring

Epigenetic modifiers

Findings

Summary and conclusions