The Optimal Condition of Poly(I: C)-Induced Knockout of Cre Recombinase for Mx1-Cre/ Cre-loxP Mice

Abstract BackgroundThe Cre-loxP system is widely applied for conditional knockout mice, commonly used to study the function of specific genes. Although some different promoters drive Cre expression, the poly(I: C)-inducible Mx1-Cre is the most commonly used to delete the target gene in experimental hematology. However, the optimal induction knockout condition for Mx1-Cre/ Cre-loxP mice using the Poly(I:C)-inducible Cre-loxP conditional system remains unclear. Here, we present two different components and three injection protocols of poly(I: C) to find the optimized condition. ResultsThe results showed that the better knockout efficiency of Cre-loxP in mice injected with pure poly(I: C) has than those injected with poly(I: C) with some components. From the perspective of lethal genes (Brg1), data showed that mice injected with a single high dose (500 µg) of pure Poly (I:C) had a lower knockout rate. For mice injected media-dose (10µg/g) poly(I: C) triple, which induced a high knockout rate, but the mortality rate was still high. Importantly, the mice injected low-dose (6µg/g) poly(I: C) triple, both the knockout rate and survival rate of mice was high. Similarly, the knockout rate of non-lethal mice injected with media-dose (10µg/g) or low-dose (6μg/g) poly(I: C) triple was very high, but injected with a single high dose (500 µg) of pure poly(I: C) had a low knockout rate. ConclusionOur studies provided the optimized condition for using poly(I: C)-inducible effective knockout and maintaining the survival rate for the Cre-loxP mice, which might be applied in other knockout mice for this system to ensure both the gene knockout and the mice survival.