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Efficiency comparison of B6(Cg)-Tyrc-2j /J and C57BL/6NTac embryos as hosts for the generation of knockout mice.

Transgenic research (2021-04-13)
Yu'e Ma, Lei He, Lijie Xiang, Jie Zhang, Jing Wang, Wenjing Zhu, Wenni Cao, Yichen Zhu, Man Gao, Fei Zhou, Zhiwei Liu
ABSTRACT

Careful selection of the host embryo is critical to the efficient production of knockout (KO) mice when injecting mouse embryonic stem (mES) cells into blastocysts. B6(Cg)-Tyrc-2j/J (B6 albino) and C57BL/6NTac (B6NTac) strains of mice are widely used to produce host blastocysts for such procedures. Here, we tested these two strains to identify an appropriate match for modified agouti C57BL/6N (JM8A3.N1) mES cells. When comparing blastocyst yield, super-ovulated B6NTac mice produced more injectable blastocysts per female than B6 albino mice (8.2 vs. 5.4). There was no significant difference in birth rate when injected embryos were transferred to the same pseudopregnant recipient strain. However, the live birth rate was significantly higher for B6NTac blastocysts than B6 albino blastocysts (62.7% vs. 50.2%). In addition, the proportion of pups exhibiting high-level and complete chimerism, as identified by coat color, was also significantly higher in the B6NTac strain. There was no obvious difference in the efficiency of germline transmission (GLT) when compared between B6NTac and B6 albino host embryos (61.5% vs. 63.3% for mES clones; 64.5% vs. 67.9% for genes, respectively), thus suggesting that an equivalent GLT rate could be obtained with only a few blastocyst injections for B6NTac embryos. In conclusion, our data indicate that B6NTac blastocysts are a better choice for the microinjection of JM8A3.N1 mES cells than B6 albino blastocysts.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
M16 Medium, With sodium bicarbonate and lactic acid, without penicillin and streptomycin, liquid, sterile-filtered
Sigma-Aldrich
M2 medium, With HEPES, without penicillin and streptomycin, liquid, sterile-filtered, suitable for mouse embryo cell culture
Sigma-Aldrich
ESGRO® Recombinant Mouse LIF Protein, ESGRO Leukemia Inhibitory Factor (LIF) supplement for mouse ES cell culture. Each vial contains 10^7 units/ml.