In developing embryos, the type of tissue that a cell becomes is primarily determined by signals each cell receives from its neighbors. These same signals also regulate the behavior of fully functional cells in adult tissues. Defects in cell signaling are the cause of many birth defects and can also cause cancer cells to form. Although great strides have been made in understanding the molecular basis of cell signaling, most of this work has been conducted in cells that are not dividing. The effect of cell division on cell response to signals remains poorly understood. This project will help fill this crucial gap by examining the interplay between cell division and signaling. The proposed experiments will examine how proteins that receive signals from neighboring cells are moved around inside dividing cells. Because both cancer cells and embryonic cells frequently divide, the distribution of these signal-receiver proteins during cell division is likely to play a crucial role in creating embryonic cell identity and in promoting cancerous cell behaviors. This proposal will also promote intensive training of diverse undergraduate researchers in designing and carrying out independent research projects. The project will also promote public education through interactions with many well-established outreach programs in the Philadelphia area.
Cell fate induction is affected by trafficking of signal components. Recent studies have overturned the long-held assumption that membrane trafficking is shut down during mitosis. Thus, mitotic trafficking of signaling components may play a profound, largely unrecognized role in cell fate specification. The long-term goal of the PI is to understand how cell division affects inductive signal processing. This question is addressed by examining heart progenitor induction in the basal chordate, Ciona intestinalis. The PI has exploited the extreme cellular simplicity of Ciona embryos to perform high-resolution, in vivo analysis of inductive signaling mechanisms, and focuses on Fibroblast Growth Factor (FGF)-dependent induction of the heart progenitor lineage. Mitotic redistribution of FGF receptors (FGFRs) was found to promote differential heart progenitor induction. The PI hypothesizes that mitotic kinases regulate trafficking of FGFR-enriched adherent domains, and will test this hypothesis through the following specific aims: 1) Characterization of mitotic trafficking of FGFR-enriched signaling domains through image analysis of tagged proteins in live, intact embryos; 2) Delineation of the role of specific endocytic pathways in signaling domain redistribution through co-localization analysis using pathway-specific markers and targeted disruption of pathway-specific components; 3) Determination of how mitotic kinases affect endocytic trafficking of FGFR-enriched domains through targeted disruption of kinase activity. Completion of the proposed studies will provide fundamental insights regarding the interplay between division and signaling in both embryonic and stem cells.