LAUSR

A window to the embryo Mammalian embryonic development is a complex process, continuously changing in space and time. Q. Huang et al. designed an abdominal window to image mouse embryos in utero from embryonic day 9.5 to birth. Using this technique, they visualized dynamic activities during embryonic organ formation, including neurotransmission and cell division in the brain, autophagy in the retina, viral gene delivery, and placental drug transfer. They also tracked diverging fates of human and mouse neural crest cells in interspecies chimeras. Science, this issue p. 181 An abdominal window enables real-time imaging of live mouse embryos from embryonic day 9.5 to birth. Embryonic development is a complex process that is unamenable to direct observation. In this study, we implanted a window to the mouse uterus to visualize the developing embryo from embryonic day 9.5 to birth. This removable intravital window allowed manipulation and high-resolution imaging. In live mouse embryos, we observed transient neurotransmission and early vascularization of neural crest cell (NCC)–derived perivascular cells in the brain, autophagy in the retina, viral gene delivery, and chemical diffusion through the placenta. We combined the imaging window with in utero electroporation to label and track cell division and movement within embryos and observed that clusters of mouse NCC-derived cells expanded in interspecies chimeras, whereas adjacent human donor NCC-derived cells shrank. This technique can be combined with various tissue manipulation and microscopy methods to study the processes of development at unprecedented spatiotemporal resolution.