Pigs taking wing with transposons and recombinases

Table 2 Evaluation of methods for swine transgenesis

	Pronuclear (naked DNA)	Pronuclear (transposon)^a	SCNT (PFF)	Lentiviral
Live-born/embryo manipulated	10% to 15%	ND	0.05% to 1.2%	18% to 27%
Transgenic per live-born	+	++	+++	++
Integration preference	Random	Random/class specific	Random or targeted	Gene coding regions
Null/hypomorph	RNAi/DN	RNAi/DN	Gene targeting/RNAi/DN	RNAi/DN
Cargo size limitations^b	ND	ND	ND	About 8 kilobases
Integrations per live-born	Typically 1	1 to 10	Typically 1	1 to 20
Mosaicism	Often	Often	Seldom	often
Ease of vector production	++	++	++/(± HR constructs)	+
Concatemer instability	Yes	No	Yes^c	No
Precision (to the base pair)	No	Yes	No^c	Yes
Homologous recombination	No	No	Yes	No
Genome aberrations	Yes	No	No	No
Heritable expression	++	+++	++^d	++
Preimplantation screen	±	±	++^e	±
Selection required	No	No	Yes	No

^aAs observed previously in mice. ^bIncreasing size invariably decreases efficiency. ^cTargeted alleles are stable. ^dMosaicism observed in clones of clones [200]. ^eExpression in SCNT donor cells does not ensure expression in animal. DN, dominant negative translocations; HR, homologous recombination; ND, not determined; PFF, porcine fetal fibroblasts; RNAi, RNA interference; SCNT, somatic cell nuclear transfer.

ISSN: 1474-760X