All animals descended from a single-celled protozoan, yet the molecular genetic events that lead to the evolution of animal multicellularity remain a mystery. The research in this proposal will test two hypotheses relating to the evolution of multicellularity: (1) that animals and a group of protozoans called choanoflagellates share a recent common ancestor and (2) that the genes required for the transition to multicellularity evolved in the protozoan ancestors to choanoflagellates and animals. Homologs of cell adhesion and developmental regulatory genes will be isolated from a colony-forming choanoflagellate by a combination of genomics-based and homology-based strategies for gene cloning. To test whether conserved genes are important for colony formation (and potentially for the evolution of multicellularity), their functions will be disrupted at the levels of the mRNA and protein products. Cloning of cell adhesion genes will extend the history of these clinically important molecules back past the origin of animal multicellularity and lay the groundwork for mechanistic studies of colony formation.
