Mouse development taken ex utero

The study of embryonic development in mice is limited by the relative inaccessibility of embryos to manipulations and imaging. Jacob Hanna and colleagues have developed a culture protocol that allowed them to grow mouse embryos ex utero from before gastrulation (embryonic day 5.5) to hind limb formation (embryonic day 11.5), covering crucial steps in early development and organogenesis. They show that mouse embryos developed ex utero closely resemble embryos that develop in utero. Importantly, their system is amenable to genetic manipulations and live imaging. This work provides a new tool for developmental biologists to investigate key steps in embryonic development.