Transgenic overexpression of a stable Plasminogen Activator Inhibitor-1 variant
Abigail T Fahim1, He Wang, Jining Feng
1Department of Human Genetics, University of Michigan, Ann Arbor, MI, United States.
Introduction:
Plasminogen Activator Inhibitor-1 (PAI-1) is a member of the Serine Protease Inhibitor (SERPIN) gene family and a key regulator of fibrinolysis. PAI-1 is unique among SERPINs in its spontaneous transition to a latent, inactive state, with a half-life of approximately 2 hours under physiologic conditions. The biologic importance of the PAI-1 transition to latency is unknown. This study aimed to engineer transgenic overexpression of a stable murine PAI-1 variant to examine the physiologic effects in vivo from delayed transition of PAI-1 to latency.
Materials And Methods:
Ten independent transgenic lines were generated with expression of a stable PAI-1 variant driven by the hybrid CMV/chicken beta-actin promoter.
Results:
Plasma PAI-1 levels in the transgenic founders ranged from 3.1+/-0.1 ng/mL to 1268.8+/-717.0 ng/mL. Quantitative PCR analysis in 3 transgenic lines demonstrated elevated PAI-1 mRNA in multiple tissues, with the highest increases observed in liver, brain, heart, and kidney. The fold-increase in PAI-1 mRNA over wild-type ranged from 2-fold to >2000-fold. Immunohistochemistry showed increased PAI-1 in liver, kidney, heart, spleen, and lung. Histologic examination of transgenic mice showed no evidence of thrombosis. The two founders with the highest plasma PAI-1 levels failed to produce any transgenic offspring that survived to weaning, although genotyping of expired pups revealed successful transmission of the transgene.
Conclusion:
These results suggest that high expression of a stable variant of PAI-1 may be lethal in mice, while more moderate expression is generally well tolerated and produces no apparent thrombosis.
