Use of FOXJ1CreER2T mice for inducible deletion of embryonic node gene expression.

The ciliated cells of the node of the mouse embryo contribute to the establishment of left-right patterning via generation of leftward laminar fluid flow and initiation of a left-sided morphogen gradient. Here, we identify FOXJ1CreER(2T) mice in which expression of Cre recombinase is directed to ciliated node cells. The data demonstrate that foxj1 is expressed specifically in the node throughout the developmental window critical for left-right patterning. In transgenic embryos, Cre expression is detected by immunohistochemistry in ciliated cells of the node. Rosa26R reporter mice, in which expression of lacZ is activated only after Cre-mediated recombination, demonstrate strong and uniform labeling at the node when crossed with FOXJ1CreER(2T) mice. Cell labeling occurred as early as 0- to 2-somite stages, specifically within cells of the node, and recombination was highly efficient in response to tamoxifen. FOXJ1CreER(2T) transgenic mice represent a new genetic tool for the analysis of node-specific gene expression and will also be valuable in the study of node cell lineage and temporal cell fate mapping.