Strain Detail: lox-Eisuke mice

The lox-Eisuke mice are transgenic mice expressing the probe which is consisted of cytoplasm-localized föster (or fluorescence) resonance energy transfer (FRET) biosensor monitoring ERK activity added with lox-tdKeima. Extracellular signal-regulated kinase (ERK) is a member of MAPK familiy and related to cellular growth and differentiation, especially plays an important role in oncogene signal transduction cascade. This strain expresses Keima fluorescent protein under the control of CAG promoter in almost all tissues. These mice are able to switch expression tissue-specifically from Keima fluorescent protein to FRET biosensor by mating with tissue-specific Cre-expressed mouse. It's possible to measure ERK activity spatially and temporally in fetal or adult various tissues by live imaging observation of this strain in the two-photon microscopy. This strain expects not only to analyze the signal transduction cascade in live animals, but also apply drug development such as the pharmacodynamic analysis targeting signal molecules, because these mice are showed rich expression in primary cultured cells derived from various tissues. In the case of using epithelial tissues when you detect the difference of ERK activity in cell lines, nucleus-localized FRET biosensor is easier to use. However, it's necessary to use cytoplasm-localized FRET biosensor if you want to observe cell forms. FRET biosensor generally can't use for fixed samples.

1. Kamioka Y, Sumiyama K, Mizuno R, Sakai Y, Hirata E, Kiyokawa E, and Matsuda M. Live imaging of protein kinase activities in transgenic mice expressing FRET biosensors. Cell Struct. Funct. 2012; 37: 65-73. [PMID: 22277578]