Episomal maintenance of a bovine papilloma virus vector in transgenic mice.

Elbrecht, A; DeMayo, Francesco J.; Tsai, M J; O'Malley, B W

doi:10.1128/mcb.7.3.1276

Cited by 14 publications

(4 citation statements)

References 13 publications

(18 reference statements)

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“…The production of extrachromosomal structures and their propagation to the next generation have been reported in transgenic animals obtained by SMGT in mammals (Kuznetsov et al, 2000), birds (Rottmann et al, 1992), fish (Khoo et al, 1992), and insects (Robinson et al, 2000) and also, in some cases, by DNA microinjection in mammals (Kiessling et al, 1986;Elbrecht et al, 1987), amphibia (Etkin and Pearman, 1987), fish (Culp et al, 1991), nematodes (Mello et al, 1991), and insects (Nikolaev et al, 1993). A significant implication of the present work for SMGT experiments is that the rate of positive animals may be found to vary over time, and in particular may be higher among younger animals, while progressively decreasing among older ones; in other words, animals that were positive in an early screening may be classified as negative upon subsequent analysis.…”

Section: Discussionmentioning

confidence: 99%

Generation of biologically active retro‐genes upon interaction of mouse spermatozoa with exogenous DNA

Pittoggi

Beraldi

Sciamanna

et al. 2006

Molecular Reproduction Devel

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Mature spermatozoa of most animal species can spontaneously take up foreign DNA molecules which can be delivered to embryos upon fertilization. Following this procedure, transgenic animals of various species have been generated. We recently discovered a reverse transcriptase (RT) activity in mouse spermatozoa that can reverse-transcribe exogenous RNA molecules into cDNA copies. These cDNA copies are transferred to embryos at fertilization, mosaic propagated as non-integrated structures in tissues of founder individuals and further transmitted to F1 progeny. Reverse-transcribed sequences behave as functional genes, being correctly expressed in tissues of F0 and F1 animals. To learn more about this mechanism and further characterize the reverse transcription step, we have now incubated spermatozoa with a plasmid harboring a green fluorescent protein (EGFP) retrotransposition cassette interrupted by an intron in the opposite orientation to the EGFP gene. We found that reverse-transcribed spliced EGFP DNA sequences are generated in sperm cells and transmitted to embryos in IVF assays. After implantation in foster mothers, embryos developed into mice that expressed EGFP in the blood vessel endothelia of a variety of organs. The EGFP-encoding cDNA sequences were detected in positive tissues as extrachromosomal mosaic-propagated structures, maintained in low-copy number (<1 copy/genome), and mosaic transmitted from founders to the F1 progeny. These results indicate that an efficient machinery is present in mature spermatozoa, which can transcribe, splice, and reverse-transcribe exogenous DNA molecules. This mechanism is implicated in the genesis and non-Mendelian propagation of new genetic information besides that contained in chromosomes.

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Section: Discussionmentioning

confidence: 99%

Generation of biologically active retro‐genes upon interaction of mouse spermatozoa with exogenous DNA

Pittoggi

Beraldi

Sciamanna

et al. 2006

Molecular Reproduction Devel

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“…In particular, transgenic sequences can generate extrachromosomal structures that are transmitted to the next generation, as documented in studies of transgenic mammals, (62,98) birds, (21) fish (19) and insects (56) obtained by SMGTand, in certain cases, by DNA microinjection. (99,100) The genesis of such extrachromosomal structures in transgenic animals, and their sexual transmission to the progeny, are unclear. According to the model, transgenic episomal DNA is thought to represent the product of an endogenous RT activity.…”

Section: Endogenous Reverse Transcriptase Activitiesmentioning

confidence: 99%

Sperm‐mediated gene transfer: Applications and implications

2005

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Recent developments in studies of sperm-mediated gene transfer (SMGT) now provide solid ground for the notion that sperm cells can act as vectors for exogenous genetic sequences. A substantive body of evidence indicates that SMGT is potentially useable in animal transgenesis, but also suggests that the final fate of the exogenous sequences transferred by sperm is not always predictable. The analysis of SMGT-derived offspring has shown the existence of integrated foreign sequences in some cases, while in others stable modifications of the genome are difficult to detect. The appearance of SMGT-derived modified offspring on the one hand and, on the other hand, the rarity of actual modification of the genome, suggest inheritance as extrachromosomal structures. Several specific factors have been identified that mediate distinct steps in SMGT. Among those, a prominent role is played by an endogenous reverse transcriptase of retrotransposon origin. Mature spermatozoa are naturally protected against the intrusion of foreign nucleic acid molecules; however, particular environmental conditions, such as those occurring during human assisted reproduction, can abolish this protection. The possibility that sperm cells under these conditions carry genetic sequences affecting the integrity or identity of the host genome should be critically considered. These considerations further suggest the possibility that SMGT events may occasionally take place in nature, with profound implications for evolutionary processes.

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“…A possible explanation is that in the male the foreign DNA is present as an episome. Episomal maintenance has already been Transgenics after lipid transfection 213 described on some rare occasions (Rassoulzadegan et al, 1986;Elbrecht et al, 1987). We are more inclined, though, to accept that it is integrated, but in such a small number of cells that its visualisation is very difficult.…”

Section: Discussionmentioning

confidence: 99%

Generation of transgenic mice by transfection of pronuclear embryos using lipid-DNA complexes

Carballada

Relloso

Esponda

2002

Zygote

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We had previously developed a methodology to introduce foreign DNA into mouse eggs and embryos using cationic lipids as vectors. In this report we use this technique to produce transgenic animals. Mouse embryos at the pronuclear stage were transfected using a mixture of a plasmid DNA, encoding for a nuclear form of β-galactosidase, and a commercial lipid transfection reagent. Embryos were washed and incubated overnight. Those that cleaved and develop to the 2-cell stage of normal appearance were transferred to the Fallopian tubes of pseudopregnant foster mothers. We analysed a total of 158 offspring and found two, a female and a male, to be transgenic (1.27% of the total). Integration of the foreign DNA in the female was showed by Southern blot. Both animals expressed the lacz in several organs, but none of them either displayed expression in the germ cells or transmitted the transgene to their offspring. Taken together our results show that lipid transfection can generate transgenic mice, but the efficiency needs to be improved for this method to be widely applied.

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Episomal maintenance of a bovine papilloma virus vector in transgenic mice.

Cited by 14 publications

References 13 publications

Generation of biologically active retro‐genes upon interaction of mouse spermatozoa with exogenous DNA

Generation of biologically active retro‐genes upon interaction of mouse spermatozoa with exogenous DNA

Sperm‐mediated gene transfer: Applications and implications

Generation of transgenic mice by transfection of pronuclear embryos using lipid-DNA complexes

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