Transposable elements in fish functional genomics: technical challenges and perspectives

Table 1 Reported performance of various transposable elements in zebrafish

Element	Element size^a	Cargo size^b	Germline transgenesis^c	Inserts per F₁	Genomic re-transposition in germline^d	Reference
Tc3	0.9 kb	About 2 kb	8% (40)^GFP+PCR			[2]
mariner	0.1 kb [63]	1.3 kb	33% (12)^PCR			[1]
SB	0.4 kb	1.4 kb	31% (42)	2		[4]
		4.5 kb	10% (202)			[4]
		1.4 kb	39% (26)			[8]
		1.3 kb	24% (330)			[8]
		1.2 kb	35% (23)			[8]
Tol2	2.8 kb	2.2 kb	50% (10)			[7]
	2.8 kb	1.2 kb	51% (156)^GFP+PCR	6		[7]
	2.8 kb	2.7 kb	29% (7)			[7]
	0.4 kb	2.2 kb	70% (10)			[11]
	0.35 kb	2.2 kb	60% (10)			[11]
	1.1 kb	10.6 kb	83% (6)			[11]
	3.2 kb	1.2 kb	16% (230)		>10%	[9]
Ac/Ds	0.6 kb	3.1 kb	58% (111)	4	>77%	[6]
		6.5 kb	42% (12)
Retroviral vectors	About 2 kb	About 3.5 kb	83% (133)	11		[64]

^aThe combined size of 5' and 3' cis sequences of the element. ^bThe size of the nontransposon DNA fragment confined between the 5' and 3' cis sequences (excluding the letter). ^cAll transposon-mediated transgenesis data were produced in an essentially similar experimental setup. In each case the transposon DNA and the transposase RNA were co-injected into fertilized zebrafish eggs. The founders were outcrossed to the wild-type fish. Germline transgenesis was calculated as the percentage of founders that produced green fluorescent protein (GFP)-positive offspring among the total number of founders screened (shown in brackets). Except for a few cases, only the offspring expressing the GFP reporter was counted. '^PCR' indicates that no reporter gene was used; transgenic offspring was identified using polymerase chain reaction (PCR). '^GFP+PCR' indicates that the number included those expressing GFP reporter and those that were PCR-positive but did not express detectable amounts of GFP reporter. ^dIn these reports the transposase RNA was injected into fertilized eggs of a transgenic fish carrying a single transposon insert in its genome. The genomic re-transposition rates were calculated as the number of founders that produced offspring with novel enhancer trap patterns distinct from the pattern of the founder. Thus, the rates were underestimated. kb, kilobase.

ISSN: 1474-760X