Production of transgenic pigs harbouring a rat phosphoenolpyruvate carboxykinase-bovine growth hormone fusion gene.

Over the past 5 years, reports detailing the production of transgenic pigs have focussed on enhanced growth performance. Phenotypic side-effects observed in pigs harbouring chimaeric constructs containing metallothionein or Moloney murine leukaemia virus transcriptional activators fused to growth hormone (GH) structural genes have been attributed to chronic overexpression of GH. In an effort to regulate a transgene product more effectively, a liver specific 460 bp 5' flanking sequence of the rat phosphoenolpyruvate carboxykinase (PEPCK) gene was ligated to a BamHI site of the first exon of the genomic bovine GH (bGH) structural gene. Following micro-injection of the PEPCK/bGH construct into 1- and 2-cell pig zygotes. 124 offspring were produced of which 7 pigs were determined to be transgenic by dot-blot and Southern analysis. The PEPCK gene expression, in terms of tissue and developmental specificity, appears similar to that observed in PEPCK/bGH transgenic mice. Germ-line transmission was identified in 1 of 3 mated founders. Dramatic influences on backfat thickness were observed including a 41% reduction in backfat depth when compared to non-transgenic sex-matched littermate control pigs. Both the regulation and characterization of gene expression in PEPCK/bGH transgenic pigs are under investigation.