UCSF

The Adhesion family of G protein-coupled receptors (AdGCPRs) is a unique set of cell-surface receptors with relatively unknown signaling capabilities and physiological functions. Previous work has revealed physiological roles for some AdGPCRs, ranging from orchestrating planar cell polarity in Drosophila epithelium to mediating cell-extracellular matrix interactions in the developing central nervous system. Mutations in some AdGPCRs have been linked to human disease. However, most AdGPCRs remain orphans, with unidentified binding partners, unclear physiological roles, and unknown downstream signaling.

Eltd1 (also referred to as ETL) is a member of the AdGPCR subfamily known to be expressed in cardiovascular tissues including heart and blood vessels. I performed morpholino-mediated knockdown of eltd1 in zebrafish to elucidate its physiological function and attempt to gain insight into binding partners and putative signaling pathways. I found that knockdown of eltd1 in zebrafish produced a defect in the establishment of left-right (LR) asymmetry as well as the processes of convergence and extension. Using targeted morpholino injections and fluorescent timelapse microscopy, I was able to show that loss of eltd1 disrupts nodal flow in Kuppfer's vesicle, the organ responsible for establishing LR asymmetry in zebrafish. Interestingly, the early developmental phenotypes associated with eltd1 knockdown are similar to those often observed in morphants and mutants of various planar cell polarity (PCP) genes.

Eltd1 morphants also displayed defects in cardiovascular development, consistent with expression data from mouse and rat that localize eltd1 transcripts most strongly to heart and blood vessels. I sought to characterize this phenotype and implement cell-culture assays to visualize Eltd1 in primary and cultured cells. Finally, I developed a strategy to isolate N-terminal binding partners of Eltd1. This work provides a foundation for further investigation of candidate Eltd1 binding partners and putative downstream signaling pathways.