Making mosaic fish primordia by focal electroporation

The lateral line is a mechanosensory system that comprises a set of discrete sense organs called neuromasts, which are arranged in reproducible patterns on the surface of fish and amphibians. The posterior component of the system, the posterior lateral line (PLL), comprises the neuromasts on the body and tail. It develops from the migrating primordium and so can be used to examine various aspects of neural development, including the control of long-range, collective cell migration and the mechanisms underlying the establishment of appropriate connectivity. Mosaic animals are those in which one or a few cells differ genetically from all others. Several methods have been developed to generate mosaic zebrafish, which can be used in long-term fate mapping or lineage tracing experiments if the progenitor cell stably expresses a reporter gene such as green fluorescent protein. Mosaic analysis can also be used to evaluate the cell autonomy of a given mutation, confronting mutant and wild-type cells, or two different types of mutant cells, in morphogenetic mosaics. Here we present an application of electroporation, which is designed to generate mosaics in defined parts of the developing zebrafish PLL. The method is based on the idea of focal electroporation, a technique developed to introduce dyes and constructs into cells within intact tissues. Current is forced into the embryo by sealing the tip of the electrode against the enveloping cells (periderm or ectoderm depending on the developmental stage, or mantle cells in the case of neuromasts).