Cell-cell fusion is the process by which multinucleated cells called syncytia form from plasma membrane fusion of cells developmentally programmed to fuse. Cell fusion is a vital universal developmental and cellular process that occurs in a wide variety of organisms. The mechanism of and factors required for cell-cell fusion are currently under investigation in multiple model organisms and systems. C. elegans is an ideal model system for studying cell-cell fusion because one-third of their somatic cells fuse to form syncytia in an invariant and predictable spatiotemporal manner. The only currently known cellular fusogens, proteins that fuse membranes, of non-viral origin have been identified in C. elegans. The cellular fusogen EFF-1 in C. elegans is essential for epithelial cell fusion but molecules that regulate it are largely unknown. We hypothesize that EFF-1 requires cofactors for its expression in and localization to the membrane borders between fusion-fated cells, activation, and function. Undergraduate research students initiated genetic screens to search for potential mutants with the intention of disseminating these mutants to additional students for characterization. We performed an enhancer modifier genetic screen using a C. elegans strain (
eff-1(
oj55)) that expresses an intermediate loss-of-function phenotype. We induced mutations within
eff-1(
oj55) animals using EMS. We then screened for the "dumpy" strong loss-of-function phenotype that can result from an increase in reduced cell fusions, which we anticipated was caused by mutation in genes involved in regulating EFF-1 and cell-cell fusion. Finally, we investigated if isolated mutants showed a decrease in epithelial cell fusion with confocal fluorescence microscopy of epithelial cell membranes in syncytial tissues such as the hypodermis and vulva. We concluded that our initial candidate enhanced strong loss-of-function cell-cell fusion mutants were not "dumpy" because of a reduction of cell-cell fusions. We plan to continue our enhancer genetic screen of
eff-1 intermediate loss-of-function mutants. In addition, we will begin a suppressor genetic screen of these mutants to expand our efforts in isolating mutations in
eff-1 regulatory molecules. Once we isolate such mutations, we will map and identify the mutations that are enhancing or suppressing the loss of
eff-1 function and further characterize their effects on cell-cell fusion and
eff-1 expression, localization, and function.