Optimization and in vitro validation of EGFP expression controlled by porcine insulin promoter / 中国实验动物学报

ABSTRACT

Objective Getting the robust exogenous gene expression vector under the control of porcine insulin promoter, and to lay the foundation for pancreaticβ-cells specific transgene expressing pigs.Method Using porcine insu-lin promoter ( PIP, 1500 bp of the 5′UTR from the porcine INS gene including the first exon and the first intron) to con-struct expression vector, the HindIII restriction site which connected the sequences of PIP and EGFP was designed before ATG, named PIP-HindIII-EGFP.Considering that the different location of restriction site may affect the expression efficien-cy of the transgene, we optimized the expression vector.Firstly the HindIII restriction site was deleted to realize the seam-less connection of PIP and EGFP,the vector was named PIP-EGFP.Also we mutated the 3′intron splicing acceptor site( SA) of the first intron into HindIII restriction site, named as PIP-SA( M)-EGFP.Three different EGFP expression vectors were respectively transfected MIN-6 mouse pancreatic β-cells, pig ear fibroblasts and kidney cells.The transfected cells were cultured for 48 h and harvested for RT-PCR, flow cytometry and Western blot analysis, to analyze and compare the expres-sion efficiency of vectors.Results After transfection,green fluorescence was observed only in MIN-6 mouse pancreaticβ-cells.RT-PCR analysis and product sequencing showed that the three expression vectors did have different stability with in-tron splicing.The PIP-HindIII-EGFP construct and PIP-EGFP vector produced two kinds of mRNA with the first intron spliced and no spliced, indicating the instability of intron splicing.Mutation of the PIP splice site would cause the first in-tron not spliced, while flow cytometry and Western blot displayed that the mutation induced a most efficient expression of the downstream gene.Conclusions A robust and specific β-cells expression vector has been successfully generated by mutating the intron splicing acceptor site of the porcine insulin promoter.It provides the foundation for preparation of pigs with pancreaticβ-cells specifically expressing the transgene.