Distinguishing Functional Roles of Nup93 Paralogs in Tissue Identity and Growth

Julia Hartmann

Program: Master’s Program in Cell and Molecular Biology
Date: Monday, May 4, 2026
Time: 9:00am
Location: Donald P. Shiley BioScience Center (BSCI)
Zoom: https://SDSU.zoom.us/j/86176861891

Abstract

The nuclear pore complex (NPC) is a highly conserved macromolecular structure that spans the nuclear lipid bilayer membrane. The NPC comprises 30 different types of proteins called nucleoporins (Nups), which are involved in nucleocytoplasmic transport, chromatin organization, gene expression regulation, DNA repair, RNA processing and quality control, and cell cycle control. Interestingly, Drosophila contains two orthologs of human Nup93, Nup93-1 and Nup93-2, suggesting that flies have evolved distinct functions for each paralog.

Understanding the paralog’s unique roles will provide greater insight into diverse functions of human Nup93, which has been linked to cancer and kidney disease. Nup93 is currently known for its essential role in NPC formation and association with chromatin, including at Polycomb-silenced domains. The differences between Nup93-1 and Nup93-2 in Drosophila are yet to be fully established or characterized. Our preliminary evidence suggests that while both contribute to nuclear pore architecture, they differ in their roles in signaling pathways and gene expression.

We found that the loss of Nup93-2 exhibits large, tumor-like structures and irregularities in larval wing discs. Consistently, the RNA sequencing data revealed an upregulation of the JAK/STAT and Wingless signaling pathways specifically in Nup93-2 RNAi-depleted tissue. The tumor-like phenotype and the hyperactivation of the JAK/STAT pathway suggests that Nup93-2 plays a unique role in signaling or gene silencing, relative to Nup93-1. We used RNAi-mediated knockdowns in vitro and in vivo to assess how downregulating each paralog affects NPC stability and whether upregulating the JAK/STAT pathway is independent of NPC levels and of Nup93’s structural roles. Using CRISPR-tagged HA-Nup93-1 and FLAG-Nup93-2, we also analyzed the subnuclear localization of Nup93 paralogs across different tissues via immunofluorescence and quantitative colocalization analysis to determine whether the paralogs occupy distinct NPC structures or localize with other protein complexes.

A genetic rescue experiment explored functional differences and showed that activation of the JAK/STAT pathway partially contributes to the developmental and growth phenotypes observed in the Nup93-2 knockdown. Together, these experiments reveal how the Nup93 paralogs contribute to NPC structure, signaling, and gene regulation, and identify a unique role for Nup93-2 in repressing JAK/STAT signaling and growth control.