Liver-specific and high-level expression of human serum amyloid P component gene in transgenic mice

To analyze the regulation of human serum amyloid P component (SAP) gene expression, we have produced seven transgenic mice. The 3.3 kb human SAP genes containing about 0.8 kb of 5′ and 1.5 kb of 3′ flanking region were injected into fertilized eggs of C57BL/6 mice. In five of the seven transgenic mice, human SAP was detected in the sera and serum concentrations were higher than that of human serum in three lines. The human SAP gene was expressed only in the liver. Amounts of human mRNA in the liver and serum concentrations of human SAP were roughly proportional to the copy number of the integrated gene. Human SAP production lowered the serum levels of mouse endogenous SAP. With the intraperitoneal administration of lipopolysaccharide, the mRNA levels in the liver and serum levels of mouse SAP increased several-fold in both the control and transgenic mice. On the other hand, neither the mRNA nor the serum levels of human SAP increased significantly.