Codon optimized membrane cofactor protein expression in alpha 1, 3 galactosyltransferase knockout pig cells improve protection against cytotoxicity of monkey serum

Abstract

In this study, we attempted to upgrade GT(-MCP/-MCP) pig genetically to express MCP at a higher level and additionally thrombomodulin (TBM), which have respective roles as a complement regulatory protein and a coagulation inhibitor. We constructed a dicistronic cassette consisting of codon-optimized MCP (mMCP) and TBM (m-pI2), designed for ubiquitous expression of MCP and endothelium specific expression of TBM. The cassette was confirmed to allow extremely increased MCP expression compared with non-modified MCP, and an endothelial-specific TBM expression. We thus transfected m-pI2 into ear-skin fibroblasts isolated from a GT(-MCP/-MCP) pig. By twice selection using magnetically activated cell sorting (MACS), and single-cell culture, we were able to obtain clones over 90% expressing MCP. The cells of a clone were provided as a donor for nuclear transfer resulting in the generation of a GT(-MCP/-MCP)/mMCP/TBM pig, which was confirmed to be carrying cells expressing MCP and functioning as an inhibitor against the cytotoxic effect of normal monkey serum, comparable with donor cells. Collectively, these results demonstrated an effective approach for upgrading transgenic pig, and we assumed that upgraded pig would increase graft survival.