A Dominant Modifier Screen for Genetic Interactor of Jagunal in Drosophila

By: Jorge Inojoza and Judy Abuel      

Department: Physiology

Faculty Advisor: Dr. Blake Riggs 

Endoplasmic reticulum (ER) is a continuous network of membrane tubules and flattened cisternae. It is a multifunctional organelle involved in proteins and lipids synthesis, secretory proteins, and post-translational modification of proteins. Recent studies have shown that the ER is partitioned asymmetrically in proneuronal cells during mitosis in early embryonic development of Drosophila just cell fate determination. Furthermore, this asymmetric ER partitioning relies on the highly conserved transmembrane protein Jagunal (Jagn), however, the molecular pathway that drives Jagn-dependent ER partitioning is currently unknown. Here, we hypothesize that Jagn interacts with cell fate determinants to drive the generation of neuronal cell diversity. To identify possible genes that interact with Jagn, we performed a dominant modifier screen in the Drosophila compound eye. Expression of JagnRNAi in the Drosophila compound eyes results in a rough eye phenotype in 80% of the eyes examined. Based on this, we crossed a collection of deficiency lines (DF) covering the entire 3rd chromosome and examined for either enhancement or suppression of the rough eye phenotype. We have identified ten suppressors and twelve enhancers of Jagn-induced rough eye lines phenotype. We examined these DF hit and selected eight genes involved in many functions such as organelle assembly, microtubule attachment, and organelle movements. We performed a secondary dominant modifier screen in the Drosophila compound eye, using mutants of the selected target genes and mutant gene Dally gave us a similar rough eye phenotype percentage. Dally is important for neuron projection morphogenesis, and positive regulation of signal transduction. We hypothesize that Dally can be working with Jagn as a cell fate determinant. Targets will provide important insight into the molecular pathway involved in ER organization and partitioning.