Fibroblast Growth Factor Receptors (FGFRs) are a type of receptor tyrosine kinase (RTK) that control many developmental processes. These include cell proliferation, cell migration, and cell survival. Mutations to these FGFRs and their pathways in humans result in developmental disorders such as achondroplasia, craniosynostosis, and thanatophoric dysplasia. To better understand FGFR signaling specificity we use the nematode C. elegans as a model. C. elegans contain a single FGFR, EGL‐15 which is imperative for sex myoblast migration and fluid homeostasis. Defects in the processes mediated by the EGL‐15 FGFR result in striking phenotypes that can be used to discover additional signaling components of the EGL‐15 pathway. For example, hyperactivation of EGL‐15 signaling causes the worm to accumulate excessive amounts of a clear fluid in its body which is known as the Clr phenotype. The isolation of suppressors of Clr (soc) mutants has helped to identify many of the core components of EGL‐15 signaling. A previous soc screen identified the adaptor protein SEM‐5 which links RTK activation to the activation of the RAS/MAPK pathway.SEM‐5 is known to bind to EGL‐15 at two tyrosine residues (Y1009 and Y1087). However, previous work suggests that removal of these binding sites does not confer a Soc phenotype. To verify this, we utilized three different CRISPR/Cas9 mutants. One mutant contains the Y1009F mutation, the second mutant contains the Y1087F mutation, and the third mutant contains both the Y1009F and Y1087F mutations. Each of these mutations was tested for their ability to suppress the Clr phenotype associated with the hyperactivation of the EGL‐15 signaling pathway. Neither the Y1009F or Y1087F mutation alone or together, results in a Soc (suppressor of Clr) phenotype. This would suggest that a key component that links EGL‐15 to SEM‐5 has yet to been identified. We performed an additional modified suppressor screen to isolate these potential “links” between EGL‐15 and SEM‐5 and are in the process of mapping and identifying these components.Support or Funding InformationIthaca College H&S Summer Scholars, Ithaca College CSTEP and FERP Funding, NIH R15 (RGM122001A), MNEIU Student Center For Science EngagementThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.