TABLE 1.

Techniques, working mechanisms, and features for transgene pig model creation.

Technique		Mechanism	Feature	Reference
Microinjection		Injecting the DNA material into the male pronucleus	Random feature of integration	(Lavitrano et al., 1989; Stout et al., 2009a)
		Injecting the RNA material into the cytoplasm	Low efficiency on a specific structure, function, and expression regulation of genes
		Injecting proteins into the cytoplasm or pronucleus	Depends greatly on many aspects	Piedrahita, (2000)
				Le et al. (2021)
Sperm-mediated gene transfer (SMGT)		Using exogenous DNA molecules to transfer them into the oocyte at fertilization	High rate of integration with the natural combining process	Umeyama et al. (2012)
			Less damage to the embryo caused by the machine
			Large efficiency gaps occurred among species
Somatic cell nuclear transfer (SCNT)		Injecting the RNA material into the cytoplasm	Low efficiency on a specific structure, function, and expression regulation of genes	Campbell, (2002)
		Injecting proteins into the cytoplasm or pronucleus	Depends greatly on many aspects	Piedrahita, (2000)
		Injecting the RNA material into the cytoplasm	Low efficiency of genome-edited somatic cells	Le et al. (2021)
			Low efficiency on a specific structure, function, and expression regulation of genes
Gene-targeted technique	Homologous recombination	Homologous recombination between DNA sequences residing in the chromosome and newly introduced, cloned DNA sequences (gene targeting)	Allowing the transfer of any modification of the cloned gene into the genome of a living cell	(Watanabe et al., 2010; Zhou et al., 2015)
	Zinc-finger nucleases (ZFNs)		Knockout genes	Watanabe et al. (2010)
				Cermak et al. (2011)
	Transcription activator-like effector nucleases, (TALENs)		Knockout genes	Li et al. (2015)
	CRISPR/Cas9		Multiple knockout genes	(Cong et al., 2013; Ding et al., 2013; Mali et al., 2013)