Germ-line-competent embryonic stem cells of the Chinese Kunming mouse strain with long-term self-renewal ability.

Kunming (KM) mice are the most widely used strain in China. However, authentic embryonic stem cells (ESCs) from KM mice have never been available, and this hampers the genetic manipulation of this valuable mice strain. In this study, we show that KM ESCs can be efficiently derived and maintained in chemically defined N2B27 medium with the presence of two small molecules PD0325901 and CHIR99021 (2i medium). These KM ESCs exhibit all features of ESCs, including long-term self-renewal ability, expression of key molecular markers (Oct4, Nanog, and Sox2), the ability to form teratomas, and the capacity to incorporate into the developing embryo and then transmit through the germ line.