Abstract
A single layer of squamous endothelial cells (ECs), the endothelium, regulates the flow of substance and fluid into and out of a tissue. The endothelium is also involved in vasculogenesis, the formation of new blood vessels, which is a crucial process for organ development in the embryo and fetus. Because most murine mutations of genes involved in EC development cause early embryo lethality, EC-specific conditional knockout (cKO) mouse models are indispensable for in vivo studies. cKO mice including the floxed allele can be generated through advanced approaches including embryonic stem cell-mediated gene targeting or the CRISPR/Cas system. EC-specific mouse models can be generated through further breeding of floxed mice with a Cre driver line, the latest information of which is available in the Jackson Cre Repository or the EUCOMMTOOLS project. Because it takes a long time (generally 1-2 years) to generate EC-specific mouse models, researchers must thoroughly design and plan a breeding strategy before full-scale mouse experiments, which saves time and money for in vivo study. In summary, revolutionary technical advances in embryo manipulation and assisted reproduction technologies have made it easier to generate EC-specific mouse models, which have been used as essential resources for in vivo studies of the endothelium.