Cell Lineage Analyses in Living Tissues

Developmental biologists require methods for marking cell lineages as they arise in living tissues. Traditionally, lineages have been traced in fixed tissues but these observations are difficult to verify. We present a method by which a progenitor cell and all of its lineage become marked by a nuclear-localised fluorescent protein. This allows rapid estimation of the effects of genetic or physical manipulation of developing tissues. Heat shock is used to activate YFP expression in single progenitor cells which is heritable by all daughter cells in subsequent rounds of mitosis. Heat shock can be applied to specimens generally using an incubator to generate random lineage patterns or more specifically to single cells or small regions using laser activation of the lineage marking system.