THE POSSIBILITY TO ALTER THE GENETICS OF DOMESTIC ANIMALS AND FISH IN A PREDICTABLE MANNER IS CLEARLY VERY ATTRACTIVE :
- SCIENTIFICALLY, THIS RESEARCH SHOULD CONTRIBUTE TO A BETTER UNDERSTANDING OF A FOREIGN GENE IN THE GERM LINE OF ANIMALS.
- TECHNICALLY, IT SHOULD IMPROVE THE PRACTICAL METHODS OF TRANSFER.
- ECONOMICALLY, IT SHOULD PROVIDE A SHORT CUT FOR THE IMPROVEMENT OF THE GENETICS OF ANIMALS, FOR INSTANCE IN OBTAINING ANIMALS GROWING AT A FASTER RATE. IT ALSO SHOULD PROVIDE METHODS TO PREPARE MASSIVELY PROTEINS OF HIGH VALUE THROUGH MILK OF BLOOD OF TRANSGENIC ANIMALS.
Regulatory sequence from several rabbit milk protein genes have been identified. One of them, from the WAP gene (whey acidic protein) is highly efficient to direct the expression of foreign genes in the mammary gland. The rabbit WAP gene promotor has been patented. Several recombinant proteins of pharmaceutical interest have been produced in the milk of transgenic mice and rabbits (human and bovine growth hormones, EC superoxide dismutase, erythropoietin) some of them at a high level. Several litres of rabbit milk have been collected for some of the proteins. Vectors optimized for the expression of foreign genes in the mammary gland are prepared. Transgenic rabbits used as models in biomedical studies have been obtained (AIDS, atherosclerosis) and others are being prepared. In addition methods to obtain transgenic trout have been defined and promotors working in fish cells have been determened.
Genetic characteristics of domestic animals can be rapidly modified through the transfer of deoxyribonucleic acid (DNA) to fertilized ova and the development of transgenics. Biological fluids (milk, blood, egg white, etc) of transgenic animals can be an abundant source of well matured proteins of clinical and veterinary interest. These goals can be reached if specific genes, promoters and vectors are prepared, and if methods to obtain transgenic animals in various species are defined.
Recombinant genes containing different promoters and growth hormone genes were prepared and tested in cultured mammalian and fish cells and in whole transgenic salmonids. Most of the regulatory elements from mammalian genes when tested in fish cells or in fish worked only on low levels. Fish genepromoters seem to be a better choice for the future. Several fish genes were cloned and characterized. Rabbit milk and bovine complementary deoxyribonucleic acid (cDNA) and genes were isolated and sequenced. Recombinant genes containing milk gene or bovine liver gene promoters and reporter genes were expressed in mammary cells in vitro and in transgenic mice. Retroviral vectors from birds were prepared. These vectors harbouring foreign genes transfer efficiently to chickens. Conditions were established for the efficient recovery of fertilized bovine ova, their microinjection, in vitro culture and transfer to recipients, with a high rate of survival. Finally, protocols were established for efficient generation of transgenic fish.
TWO STRATEGIES WILL BE USED TO INTRODUCE A NUMBER OF GENES INTO THE GERM LINE OF THE ANIMALS :
- MICROINJECTION OF DNA,
- DELIVERY OF THE DNA BY RETROVIRUSES.
THREE GENES ARE ALREADY AVAILABLE : MOUSE METALLOTHINEIN, AND THE MMTV AND SV40 PROMOTERS. IT IS PROPOSED TO CLONE PROMOTERS FOR : HIGH LEVEL OF CALF PROTEIN SEQUENCE, HIGH LEVEL OF A SALMON PROTEIN SEQUENCE, THE RABBIT CASEIN PROMOTER AND THE SALMON AND BOVINE GROWTH HORMONE PROMOTERS.
Funding SchemeCSC - Cost-sharing contracts