Minigenes enhance heterologous expression and prevent aberrant splicing of mouse Spink1

The digestive enzyme trypsin is an important driver of pancreatitis development and progression. Inhibition of intrapancreatic trypsin activity is an attractive yet so far unsuccessful approach for the treatment and prevention of pancreatitis. Gene therapy using adeno-associated viral vector containing the human serine protease inhibitor Kazal type 1 (SPINK1) gene has shown efficacy against murine pancreatitis in preclinical experiments. To advance this method to clinical testing, viral vectors with improved inhibitor expression are needed. In this study, we investigated the effect of minigenes with single introns on the expression of the mouse Spink1 gene. We found that minigenes markedly stimulated the expression of mouse Spink1 mRNA and SPINK1 protein in HEK 293T cells transfected with plasmids and in AR42J rat pancreatic acinar cells and isolated mouse pancreatic acini transduced with adenoviral vectors. The optimal intron size for expression enhancement was 100 nucleotides. We also demonstrated that mouse Spink1 mRNA expressed from a cDNA construct underwent spurious mRNA splicing and minigenes prevented this splicing defect. However, enhancement of mouse Spink1 expression by minigenes was unrelated to the rescue of aberrant mRNA splicing. The observations will facilitate the development of advanced viral vectors harboring mouse Spink1 for preclinical therapeutic studies in mouse models of pancreatitis.