A Cis-Element in magu-2 Mediates Apical mRNA Localization via Active Transport in C. elegans

mRNA subcellular localization is a key mechanism of post-transcriptional gene regulation and is widely conserved across cell types and species. Although increasing evidence suggests that transcripts associated with epithelial polarity also undergo asymmetric subcellular distribution, the trafficking patterns and regulatory mechanisms governing this process remain elusive. MAGU-2, the Caenorhabditis elegans ortholog of the Drosophila polarity gene stardust (sdt), has previously been reported to demonstrate apical mRNA enrichment. In this study, a truncation screen of magu-2 exon 3 was performed, leading to the identification of a 270-nt SH3 domain-containing fragment that drives apical localization of both its encoded mRNA and the corresponding truncated MAGU-2 protein, indicating that this 270-nt fragment within magu-2 is sufficient to direct the apical localization of both the transcript and its protein product. Live imaging, RNAi-mediated knockdown of DHC-1, BicD, or EGAL-1, together with nocodazole treatment, revealed that this mRNA undergoes active transport and that its apical targeting is disrupted upon impairment of dynein/BicD/Egalitarian function or microtubule integrity is compromised, implicating the conserved dynein/BicD/Egalitarian axis in magu-2 mRNA trafficking. While deletion of this 270-nt element exerted no overt effect on epithelial polarity or development, these findings provide insight into the active transport of epithelial polarity- related transcripts and position magu-2 as a useful model for dissecting cis-elements and trans-acting factors modulating subcellular RNA localization.