Intellectual Merit: Building the animal body requires cells to change position in organized ways during embryonic development, but the how cells are guided as they move remains poorly understood. Dorsal intercalation in the epidermis of the C. elegans embryo is an outstanding model system for examining how cell rearrangement is controlled at the level of single cells. This proposal seeks to investigate how the rearrangement of small cohorts of dorsal epidermal cells is controlled in three ways:
(1) Identification of local cues for rearrangement: By capitalizing on the highly stereotyped anterior-posterior divisions that create the right- and left-hand rows of posterior dorsal cells, laser ablation and cell isolation experiments will identify which surrounding cells are required for posterior dorsal cells to become committed to the intercalation morphogenetic program. (2) Identification of the role of noncanonical Wnt signaling for rearrangement: Wnt pathway signals, acting at least in part through WRM-1/b-catenin, are required for correct patterning and rearrangement of the dorsal epidermis. Phenotypic defects associated with mutants for components that are known to regulate pop-1/Tcf function, including wrm-1/b-catenin, lit-1/NLK, and dsh-2/Dishevelled will be examined. gfp::pop-1/Tcf and wrm-1::gfp constructs will be used as markers for A-P (and hence right-left) asymmetries to determine when such asymmetries are established. Finally, temperature-sensitive lit-1 and wrm-1 mutants and an inducible, dominant negative pop-1 construct will be used to determine when this pathway is required to regulate dorsal intercalation. (3) Identification of the roles of SYS-1, a divergent b-catenin, in rearrangement: SYS-1 is known to modulate POP-1 activity in postembryonic contexts but is also required for dorsal intercalation. When SYS-1 is required to regulate intercalation will be determined using sys-1 overexpression constructs, which are known to reverse the polarity of POP-1 asymmetries postembryonically. Because zygotic loss of function phenotypes suggest that SYS-1 could also play a later role in regulating cell adhesion through the cadherin complex, whether SYS-1 localizes to junctions and whether it interacts with cadherin complex components will also be determined.
Broader Impacts: In addition to training of graduate students and undergraduates, including NSF-funded Research Experience for Undergraduate (REU) students and Jess Vera, a Puerto Rican-American undergraduate, movies and other data generated from this project will be incorporated into dynamic, QuickTime-based learning modules being developed as an educational outreach initiative through the Laboratory for Optical and Computational Instrumentation (LOCI) at the University of Wisconsin. Developed modules will be field-tested with students in the Biology Core Curriculum, a four-semester honors biology sequence that the PI directs. As a result of these studies, we will gain fundamental insights into how Wnt signaling components, which are highly conserved throughout the animal kingdom, regulate cell rearrangement, and the results of these studies will be translated to the undergraduate curriculum.
