Microinjection of fluorescent tracers to study neural cell lineages

The examination of cell lineages is an important step towards understanding the developmental events that specify the various cell types in the organism. The mechanisms that control which cell types are formed, their locations, and their numbers remain unknown. Analyses of cell lineage in the frog neural retina have revealed that individual precursors are multipotent and are capable of producing almost any combination of cell types. In addition to giving rise to a wide range of phenotypes, the precursors can give rise to a wide range of clone sizes. Cell lineage studies in other systems indicate that some precursors are multipotent, like those in the retina, while others appear to produce a more restricted range of descendants, perhaps even a single phenotype. These differences in the developmental potential of precursor cells suggest that the nervous system uses several strategies for producing its many cell types. Investigation of these strategies, at the cellular and molecular level, requires more than a description of the normal cell lineages. We are now exploiting the frog neural retina to perform the experimental manipulations needed to elucidate these strategies.