%0 Generic
%A Schwarz, Andre
%C Heidelberg
%D 2020
%F heidok:28384
%R 10.11588/heidok.00028384
%T Nucleoporin mRNA localization and Annulate Lamellae biosynthesis during Drosophila melanogaster oogenesis
%U https://archiv.ub.uni-heidelberg.de/volltextserver/28384/
%X Nuclear pore complexes (NPCs) are large protein assemblies that connect the eukaryotic nucleus with the cytoplasm, thus facilitating all transport between them. Besides the nuclear envelope (NE), NPCs also occur in parallel stacks of cytoplasmic membranes called Annulate Lamellae (AL) that can serve as storage, facilitating rapid nuclear growth via NE insertion during fruit fly embryogenesis. How and when AL are assembled is largely unknown. In this work, I established that AL are already abundant in late stage oocytes, and progressively accumulate throughout oogenesis specifically in the oocyte. By screening the localization of 39 nucleoporin and related mRNAs, I detected the specific enrichment of two nucleoporin and three importin encoding transcripts to AL, the NE, and previously unidentified nucleoporin granules throughout the egg chamber. Perturbation experiments revealed a dependence on active translation, but independence of an intact microtubule network on mRNA localization. Generation of GFP::Nup358 transgenic flies revealed granules with distinct partial nucleoporin contents, that are subject to microtubule-dependent transport and interactions among them. Their spatiotemporal abundance distribution is indicative of NPC precursors, and they contain partial accumulations of pore complexes within internal membranes. These granules further displayed characteristics of biomolecular condensates, including fast intra-granule dynamics, exclusion of cytoplasmic constituents, and sensitivity to 1,6-hexanediol. Both condensation state and AL assembly were dependent on Ran, a protein also fundamental for NPC assembly at the NE. Its nucleotide status throughout this is likely controlled by differential localization of its modulators RanGAP and Rcc1 to granules and cytoplasm respectively. This work thus established a molecular framework and basic sequence of events that leads to the assembly of AL, which are crucial during early development, and might have broader implications for NPC assembly also at the NE.