Visualizing developmental dynamics of nuclear morphology and transport machinery in Drosophila.

Communication between the cytoplasm and the nucleus requires a continuous exchange of molecules across the nuclear envelope (NE). The nuclear pore complex (NPC) is the gateway embedded in the NE through which cargo moves, while transport receptors mediate the passage of macromolecules through the NPC. Although their essential role as the components of the nuclear transport machinery has been extensively studied, how these factors respond to developmental and environmental cues has been underexplored. Here we tag the nucleoporin Nup96 and the transport receptor Impβ with mEGFP and mScarlet-I at their endogenous loci in Drosophila. We demonstrate the functionality of these markers in multiple tissues and offer new options for better visualization of nuclear morphology in densely packed, complex tissues. Then, we characterize the spatiotemporal dynamics of these markers in multiple developmental contexts. We find that Nup96 and Impβ form cytoplasmic puncta, whose size, numbers, and co-localization patterns change dynamically during oogenesis and early embryogenesis. Moreover, we find that the abundance of NPCs per nucleus decreases during early embryogenesis, complementing the emerging model in which NPCs play a regulatory role in development. The tools and observations described here will be useful in understanding the dynamic regulation of nuclear morphology and transport machinery in development.