August 9 – 13, 2015
“What if . . . we had cows that did not have horns? We do! This is a naturally-occurring mutation, and these are called “polled” (or, hornless) cows. This is a great benefit to the cattle industry, as this reduces the amount of trauma that cows can cause each other. Unfortunately, there are only a few types of cows that contain the mutation causing the polled phenotype. Other cows must have their horns removed to safely interact with each other in groups and their handlers. You can see that this type of “surgery” could also cause animal welfare issues.
But, what if we could transfer the naturally-occurring mutation from one type of cow to another? This can be accomplished by breeding the mutation into non-polled cattle. Keeping in mind that the time for gestation in cattle is 9 months, and then the time to sexual maturity could be another one to one and a half years, the time needed to do the number of crosses to generate this mutation in a new strain of cattle could be significant—one breeder’s lifetime. But (again, another “but”), what if we could introduce this mutation in a single generation by genetic engineering and leave no footprint behind—just this ONE MUTATION. It is now possible to do this using the CRISPR/Cas9 system; one could introduce the mutation and carefully characterize the animals that result to insure that there are no additional changes in the genome—no footprints. You could argue that this would be incredibly beneficial for animal welfare issues and for the benefit of those who care for these animals.”
This is the type of discussion that can result, based on the research presented at the Tenth Transgenic Animal Research Conference (TARC X) [http://www.cevs.ucdavis.edu/confreg/?confid=732] just completed in Lake Tahoe, California, USA. The discussions and talks centered around transgenic animals other than mice, including cows, sheep, goats and pigs, as well as avians (chickens), rabbits, and even mosquitoes! An especially valuable addition to the signature 10th Conference was the inclusion of reviews of different aspects of the technology given at the start of each session.
In the first session, Dr. Jim Murray (UC Davis, USA) reviewed how genetically engineered livestock have been developed for agriculture since the first TARC meeting in 1997. This was closely followed by a talk from Maeve Ballantyne (Roslin Institute, Scotland) about their efforts to engineer resilience to African swine fever into pigs. This disease is rapidly spreading from Africa throughout Eastern Europe. Thus, this type of genetic engineering could be critical for maintaining the health of swine herds. The following talk by Jayne Raper (CUNY, USA), was a natural extension in this session, discussing how genes encoding resistance to trypanosomiasis in non-human primates could be moved into sheep and cattle. The expectation is that such genes are critical for maintaining the health of these herds throughout Africa.
The second session was devoted to new technologies for genome engineering. It started with an excellent review from Bruce Whitelaw (Roslin Institute, Scotland). His review showed how the initial slow progress in generating precisely mutated animals has become much more rapid with the introduction of genome editing. The promise of this technology was soon demonstrated by Mark Tizard (CSIRO, Australia), who described efforts to edit the genome of poultry, and by Bhanu Teluga (University of Maryland, USA), who described his highly efficient CRISPR/Cas targeted genome editing in pigs.
After an afternoon break for hiking, shopping, boating and general fun in Lake Tahoe, there was a late afternoon poster session with submissions from throughout the world. After dinner, the evening session began with a talk from Pablo Ross (UC Davis). Pablo reviewed how pluripotent stem cells have been used to generate targeted livestock, and tantalized the audience with a promise of an upcoming publication describing a new media for growth of pluripotent stem cells from large animals, hopefully capable of generating chimeras and germline transmission. This was closely followed by talks from Franklin West (Univ. of Georgia, USA) and Jorge Piedrahita (NCSU, USA) about the use of stem cells in both pigs and chickens.
The second full day of the meeting was begun with a review by Chris Rogers (Exemplar Genetics, USA) on how genetically engineered livestock have been developed for biomedical models. Simon Bawden (SARI, AU) reported how Huntington’s disease has been recreated in sheep. This was followed by a talk from Lydia Garas (UC Davis, USA) about lysozyme transgenic goats whose milk can be used to prevent and treat intestinal diseases. After a short break, Mingjun Liu (China) described how the sheep FGF5 and MSTN genes have been altered using CRISPR/Cas9 gene editing. The final talk of the morning was from Margareth Capurro (Univ. of Sao Paulo, Brazil), where she captivated the audience with her description of the methods used to gain acceptance for release of GE mosquitoes to reduce the incidence of dengue fever in one Brazilian village. Margareth finished her talk with a most memorable jingle used as a public service announcement!
The Tuesday afternoon session was composed of talks from Eddie Sullivan (SABBiotherapeutics, USA) about the generation of humanized antibodies produced in cows, and from Lissa Herron (Roslin Institute, Scotland) about the isolation of pharmaceutical proteins from avian egg whites. These talks were then followed by an enthusiastic review from Tim Doran (CSIRO, AU) where he surveyed the advances made in engineering of the avian genome. A number of conference attendees added to their notoriety by being listed in his “Hall of Fame”! The final talk on Tuesday, given by Marie-Cecile van de Lavoir (Crystal Biosciences, USA), described the generation of transgenic chickens carrying Cre-recombinase, which can be used to delete selectable markers in vivo.
The final day of the regular conference began with a review by Kevin Wells (Univ. of Missouri, USA) of the regulations governing genetic engineered animals and the food supply. He emphasized that, in the US, while there are regulations that apply, there have not been laws passed that oversee this area, and he called for the preparation of a “white paper” by the experts in the field to advise the US government. His talk was followed by a presentation of the “Glo-fish”@ experience with obtaining US approval given by Alan Blake (Yorktown Technologies, USA). William Muir (Purdue Univ., USA) then presented his statistical model (Hazard Assessment at Critical Control Points, or HAACP) that can assess environmental risk of GE animals based on net fitness of the organism, demonstrating its effectiveness in an experiment on a model organism. He then showed its application to the Aquabounty@ salmon currently awaiting approval, showing that the fear of an accidental release is irrelevant, as the GE salmon would quickly be eliminated from the population.
The next session had talks from Jun Wu (Salk Institute, USA) on the development of pluripotent stem cells, and their use in the pig to generate humanized organs for transplant; and from Hiro Nakauchi (Stanford Univ., USA) on exploiting an “organ niche” by injecting pluripotent stem cells from one organism (rat) into another, deficient organism (Pdx1-/- mouse) to generate a xenogenic pancreas. He is now testing this process in pigs as well.
Attendees were then given another welcome afternoon off to play in the surrounding area, where there is ample opportunity for boating, biking and hiking. This being the final day of the regular conference, everyone truly welcomed this last chance to enjoy the lake and surrounding mountains.
The final session of the meeting began (after another poster session and dinner) with a review given by Heiner Niemann (Hannover, Germany), where he spoke about the use of pigs as xeno-donors for human organs. He described three major hurdles to this scenario, including immune responses, physiological incompatibilities, and the risk of transmitting zoonotic organisms. His own work is an attempt to modify the immune response by humanizing several candidate genes.
The last talk of the meeting was from Alison Van Eenennaam (UC-Davis, USA) about how the technology has progressed but the acceptance of transgenic food animals has not over the past twenty years that TARC meetings have been held. She made an eloquent request that scientists take the time to explain and assure the public that genetic engineering technology can be safe and assist the world with developing a healthy, sustainable food supply. The scientific portion of the meeting then ended with the presentation of the poster award (sponsored by the Roslin Institute) to Dorothea Aumann (Munich, Germany) for her poster on “Analyzing gamma/delta T-cell function in chicken by reverse genetics”. The award presentation was followed by a discussion of how to advance the regulatory environment.
An optional Livestock Industry Day was held the following day, 14 August, 2015, where various company representatives could share their work, interact with attending scientists, and have another enjoyable day in Lake Tahoe. All in all, it was a very informative, interesting, and pleasurable meeting. Granlibakken Conference Center [http://www.granlibakken.com], The UC Davis Department of Animal Science [http://animalscience.ucdavis.edu], Drs. Jim Murray, Elizabeth Maga, Alison Van Eenennaam and Pablo Ross should be commended for their hard work in producing such a successful gathering. The next meeting will be held August 13-17, 2017—please plan on attending!
Respectfully submitted by:
Jan Parker-Thornburg, with editing from Walter Tsark and Jim Murray