BRC Current Technology December 2017

11. First knockout MSM/Ms mouse created

Taming wild-derived mice by gene knockout

Figure 1. MSM mice before and after knockout of the nonagouti (a) gene.

Left: A MSM mouse with original agouti coat color (from RIKEN BRC website).
Right: A MSM mouse carrying a mutation of the nonagouti (a) gene. It shows a black coat color and stays on hand.

Figure 2. Results of the stay-on-hand test.

Comparison of the stay-on-hand test in wild-type (WT) mice and nonagouti (a) knockout (KO) mice. Genotype, but not sex, had a significant effect on the duration of time on the hand. The dashed lines represent the average values.

Assisted reproductive technologies have been developed for wild derived strains maintained at RIKEN BRC. Superovulation and embryo transfer techniques are now routinely used for maintenance, preservation, and distribution of more than 40 wild-derived strains [1, 2].
Recently, the CRISPR/Cas9 system has been applied for generation of knockout wild-derived MSM/Ms mice and met with success. Two homozygous knockout strains are now available from RIKEN BRC.

RBRC10151 MSM-A<em1Ogu>
RBRC10152 MSM-A<em2Ogu>

Both are knockout strains for the nonagouti (a) gene with a black coat color (Fig. 1). They are tamer than the original strain (Fig. 2). As other phenotypes including body weight and serum biochemical values are not different from those of the original strain, they can be broadly used as MSM mice with easy handling.

References	[1]	Hasegawa A, Mochida K, Matoba S, Yonezawa K, Ohta A, Watanabe G, Taya K, Ogura A. Efficient production of offspring from Japanese wild-derived strains of mice (Mus musculus molossinus) by improved assisted reproductive technologies. Biol Reprod.; 86(5):167, 1-7, 2012.
	[2]	Mochida K, Hasegawa A, Otaka N, Hama D, Furuya T, Yamaguchi M, Ichikawa E, Ijuin M, Taguma K, Hashimoto M, Takashima R, Kadota M, Hiraiwa N, Mekada K, Yoshiki A, Ogura A. Devising assisted reproductive technologies for wild-derived strains of mice: 37 strains from five subspecies of Mus musculus. PLoS One.; 9(12):e114305, 2014.
	[3]	Hirose M, Hasegawa A, Mochida K, Matoba S, Hatanaka Y, Inoue K, Goto T, Kaneda H, Yamada I, Furuse T, Abe K, Uenoyama Y, Tsukamura H, Wakana S, Honda A, Ogura A. CRISPR/Cas9-mediated genome editing in wild-derived mice: generation of tamed wild-derived strains by mutation of the a (nonagouti) gene. Sci Rep.; 7:42476, 2017.

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