PHENOTYPIC AND GENOTYPIC STABILITY OF MULTIPLE LINES OF TRANSGENIC PIGS EXPRESSING RECOMBINANT HUMAN PROTEIN-C

The genotypic and phenotypic stability of four lines of transgenic pig s expressing recombinant human protein C in milk was examined. Two lin es were established with a construct consisting of a 2.6 kb mouse WAP promoter and a 9.4 kb human protein C genomic DNA. Two lines were esta blished with another construct consisting of a 4.1 kb mouse WAP promot er and a 9.4 kb human protein C genomic DNA. Genotypic stability was m easured by transgene copy number transmission. Outbred offspring havin g a single transgene integration locus were established from a founder having three independent, multicopy loci. Phenotypic stability over m ultiple lactations was defined by the combination of recombinant human protein C expression levels and the isoform signature of recombinant human protein C in western blots. Both cDNA and genomic human protein C transgenes gave similar ranges of expression levels of about 100-180 0 mu g ml(-1). Within a given outbred lineage having a single loci for the cDNA transgene, the expression levels ranged between 100-400 mu g ml(-1). Western blots of reduced recombinant protein C revealed that single chain content was not dependent on expression level and was con sistent within each transgenic line, but varied between transgenic lin es. This suggests that native swine genetics may play a role in select ion of production herds with optimal post-translational proteolytic pr ocessing capability. Although swine are not conventional dairy livesto ck, it is agreed that the short generation times, multiple offspring p er litter, stable paternal transmission of the transgene, and milk pro duction capabilities of swine offer distinct advantages over conventio nal dairy livestock for the establishment of a herd producing a therap eutic recombinant protein.