The primary aim of this research is to understand the developmental mechanisms which account for the intricate cellular composition of the mature nervous system. In the leech, individual neurons arise from precise cell lineages and express unique combinations of differentiated characteristics. These neuronal cell lineages have only been partially described, and one of the objectives of the research will be to characterize the complete sequence of cell divisions which lead to the formation of a small number of identified neurons. The investigators will then perform embryonic cell ablations in order to ascertain whether the number and identity of the neurons produced by a given lineage are determined by cell interactions or by factors that are intrinsic to precursor cells. The cellular basis of those interactions and/or intrinsic factors will be studied in further detail. In addition, the P.I.'s will investigate the way in which different cell lineages communicate in order to bring about coordinated patterns of neurogenesis. In particular, they will examine the spatial coordination of homologous cell lineages located in different portions of the nervous system. Results obtained from this work will advance our understanding of the way in which cellular diversity and specificity arise during neural development.
