Meeting Abstract

87.3  Monday, Jan. 6 10:45  Notch signaling may have evolved to control cellular differentiation and growth during development of metazoan animals LAYDEN, MJ*; MARTINDALE, MQ; University of Florida layden@whitney.ufl.edu

The emergence of multicellular animals possessing distinct differentiated cell types requires a mechanism to regulate the cellular decision to differentiate or remain undifferentiated. Notch is a novel metazoan signaling pathway used to regulate cellular differentiation during animal development. However, essentially all functional characterization has been conducted in bilaterian species. Though it is likely Notch has been co-opted into multiple developmental programs, one way to generalize Notch signaling is that the cell(s) in which the Notch receptor is activated remain undifferentiated and are often characterized as proliferative. This observation suggests Notch may be a core conserved metazoan regulator of cellular differentiation. Thus, characterization of Notch signaling in more basally branching animals is critical for reconstructing putative ancestral Notch functions. To address this issue we investigated Notch during neural development of the cnidarian sea anemone Nematostella vectensis. We find that cells experiencing high Notch fail to express differentiated neural markers. However, we have currently found no correlation between active Notch signaling and cell proliferation. We find evidence that the Notch ligand Delta also functions as a receptor, suggesting that Notch signaling in Nematostella is bidirectional. Misexpression of an activated form of Delta induces neural differentiation and inhibits cell proliferation. The conserved role for Notch-Delta signaling as a regulator of cellular differentiation in basally branching animals suggests that one of the driving forces for the emergence of Notch signaling in the metazoans was a general mechanism to regulate the delicate balance of growth and differentiation during development of multicellular animals.