Photoactivation cell labeling for cell tracing in avian development.

INTRODUCTIONTracing cell movements in a living embryo or embryo slice culture remains a challenging problem due to difficulties in cell accessibility and in accurate delivery of fluorescent labels into an individual cell or subgroup of cells. Here, we describe a photoactivation cell-labeling technique in avian embryos that allows for selective marking of individual cells or groups of cells at precise times and spatial locations normally not accessible using previous techniques. The current protocol is also less invasive than previously described methods. We provide details of fluorescent protein delivery into cells of interest utilizing microinjection and in ovo electroporation, as well as the optical parameters needed for photoactivation and imaging of both single- and dual-color photoactivatable fluorescent proteins (PAFPs). We present applications to label single cells and small subgroups of cells throughout the head and trunk of the developing vertebrate embryo, using the avian neural crest as our model cell population.