Scientists report new strategy to create genetically-modified animals

Sep 20, 2007

Researchers at the University of Pennsylvania School of Veterinary Medicine have demonstrated the potential of a new strategy for genetic modification of large animals. The method employs a harmless gene therapy virus that transfers a genetic modification to male reproductive cells, which is then passed naturally on to offspring.

Ina Dobrinski, associate professor and director of the Center for Animal Transgenesis and Germ Cell Research at Penn Vet, and her colleagues introduced adeno-associated virus, AAV, to male germline stem cells in both goats and mice. The study showed that AAV stably transduced male germ line stem cells and led to transgene transmission through the male germ line.

The findings, available online in The FASEB Journal and in the February 2008 print edition, are the first report of transgenesis via germ cell transplantation in a non-rodent species, a promising approach to germ line genetic modification. It also demonstrates that germline transduction and germ cell transplantation in large animals provides an approach that is potentially less costly than microinjection and cloning, the traditional methods used to generate transgenic large animal models for biomedical research.

Researchers used mouse germ cells harvested from experimentally induced cryptorchid donor testes that were then exposed in vitro to AAV vectors carrying a green fluorescent protein transgene and transplanted to germ cell-depleted recipient testes, resulting in colonization of the recipient testes by transgenic donor cells.

When researchers mated these recipient males with wild-type females, 10 percent of offspring carried the gene originally introduced into the transplanted germ cells, meaning the genetic modification had been passed on. To broaden the approach to non-rodent species, AAV-transduced germ cells from goats were transplanted to recipient males in which endogenous germ cells had been depleted by fractionated testicular irradiation. Transgenic germ cells colonized recipient testes and produced transgenic sperm. When semen was used for in vitro fertilization, 10 percent of embryos were transgenic.

“Initially, the team used the established germ cell transplantation model in the mouse to investigate whether AAV-mediated transduction of germ cells was possible and could result in transgene transmission,” Dobrinski said. “To broaden the applicability of the results for different mammalian species, the approach was then applied to a large animal species in which germ cell transplantation-mediated transgenesis would provide an important alternate approach to the generation of transgenic animal models for biomedical research.”

Currently, somatic cell nuclear transfer or pronuclear injection is used to generate transgenic animals. These inefficient and difficult methods also carry a risk of producing offspring with developmental abnormalities. The use of retroviral or lentiviral vectors has been reported in rodents, but it requires that animals be handled and maintained under higher biosafety precautions that render this approach less practical for transgenesis in large animal species. In contrast, animals exposed to AAV can be maintained under standard husbandry conditions.

AAV is a dependent virus that carries no disease and causes only a very mild response from the immune system. Because AAV can infect both dividing and non-dividing cells and passes its genome, it is considered an excellent candidate for use in gene therapy.

Source: University of Pennsylvania

Explore further: Alaska's popular walrus cam streams again after a decade

Related Stories

Controlling the internal structure of mitochondria

May 05, 2015

(Phys.org)—One might think of mitochondria as devices for transporting electrons to their lowest energy state. Little bags of finely-tuned respiratory chain subunits which combine electrons extracted from ...

Upside down and inside out

Apr 27, 2015

Researchers have captured the first 3D video of a living algal embryo turning itself inside out, from a sphere to a mushroom shape and back again. The results could help unravel the mechanical processes at ...

Viral proteins may regulate human embryonic development

Apr 21, 2015

A fertilized human egg may seem like the ultimate blank slate. But within days of fertilization, the growing mass of cells activates not only human genes but also viral DNA lingering in the human genome from ...

Recommended for you

For pollock surveys in Alaska, things are looking up

14 hours ago

Shelikof Strait, in the Gulf of Alaska, is an important spawning area for walleye pollock, the target of the largest—and one of the most valuable—fisheries in the nation. This year, a team of NOAA Fisheries ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.