A transgenic pig model expressing a CMV-ZsGreen1 reporter across an extensive array of tissues

Since genetic engineering of pigs can benefit both biomedicine and agriculture, selecting a suitable gene promoter is critically important. The cytomegalovirus (CMV) promoter, which can robustly drive ubiquitous transgene expression, is commonly used at present, yet recent reports suggest tissue-specific activity in the pig. The objective of this study was to quantify ZsGreen1 protein (in lieu of CMV promoter activity) in tissues from pigs harboring a CMV-ZsGreen1 transgene with a single integration site. Tissue samples ( n=35) were collected from neonatal hemizygous ( n=3) and homozygous ( n=3) piglets and ZsGreen1 abundance was determined via immunoblotting. ZsGreen1 was detected in all tissues, except hypothalamus, kidney cortex and oviduct. The expression patterns of homozygous and hemizygous piglets were similar ( P>0.05). However, quantification revealed that ZsGreen1 protein levels were tissue-specific. Within neural/endocrine tissues, ZsGreen1 abundance was highest in the anterior pituitary gland, intermediate in the cerebellum and lowest in the cerebrum, spinal cord and posterior pituitary ( P<0.05). In the digestive system, ZsGreen1 was more abundant in the salivary gland than esophagus, stomach, pancreas, duodenum, jejunum, ileum, spleen, colon, gallbladder and liver ( P<0.05). Interestingly, ZsGreen1 amounts also differed within an organ ( i.e., the right ventricle had 3-fold higher levels than the other heart chambers; P<0.05). These results provide useful information for the use of the CMV promoter to drive transgene expression in the pig. Moreover, this swine model represents a novel resource of ZsGreen1-labeled organs and a valuable tool to advance genome editing research.