RAB13 mRNA compartmentalisation spatially orients tissue morphogenesis

Abstract

Polarised targeting of diverse mRNAs to cellular protrusions is a hallmark of cell migration. Although a widespread phenomenon, definitive functions for endogenous targeted mRNAs and their relevance to modulation of in vivo tissue dynamics remain elusive. Here, using single‐molecule analysis, gene editing and zebrafish live‐cell imaging, we report that mRNA polarisation acts as a molecular compass that orients motile cell polarity and spatially directs tissue movement. Clustering of protrusion‐derived RNAseq datasets defined a core 192‐nt localisation element underpinning precise mRNA targeting to sites of filopodia formation. Such targeting of the small GTPase RAB13 generated tight spatial coupling of mRNA localisation, translation and protein activity, achieving precise subcellular compartmentalisation of RAB13 protein function to create a polarised domain of filopodia extension. Consequently, genomic excision of this localisation element and perturbation of RAB13 mRNA targeting—but not translation—depolarised filopodia dynamics in motile endothelial cells and induced mispatterning of blood vessels in zebrafish. Hence, mRNA polarisation, not expression, is the primary determinant of the site of RAB13 action, preventing ectopic functionality at inappropriate subcellular loci and orienting tissue morphogenesis.

RNA localization and co‐translational interactions control RAB 13 GTP ase function and cell migration

“…Overall, our data highlight a role for local translation in directing Rab GTPase activation and suggest that the microenvironment into which a protein is synthesized can affect its regulation and downstream function. Concurrent work by Costa et al (2020) has identified a similar GA‐rich region involved in localization of the RAB13 RNA in endothelial cells and has demonstrated its importance during zebrafish blood vessel morphogenesis, further supporting the generality and physiological relevance of the mechanism described here.…”

Collective cancer cell invasion requires RNA accumulation at the invasive front

“…Furthermore, RNA accumulation is accompanied by a concentration of various RNA-binding proteins and translation factors at the leading edge and protrusions of migrating cells ( 6 – 9 ). RNA accumulation at protrusions is functionally relevant since preventing protrusion localization of certain RNAs or inhibiting translation at protrusions leads to protrusion destabilization and impedes the efficiency of cell migration ( 6 , 7 , 10 – 12 ).…”

The kinesin KIF1C transports APC-dependent mRNAs to cell protrusions

“…Similar to what has been described for other localized RNAs, sequences within the 3'UTR of APC-dependent RNAs are necessary and sufficient for targeting to the periphery (Mili et al, 2008). Specifically, interfering with or deleting particular GA-rich regions is sufficient to disrupt peripheral localization and perturb cell movement in various systems (Moissoglu et al, 2020;Costa et al, 2020;Chrisafis et al, 2020). Furthermore, localization to the periphery requires the microtubule cytoskeleton and in particular a subset of stable, detyrosinated microtubules (Wang et al, 2017;Moissoglu et al, 2019).…”

“…The kinesin KIF1C controls a widespread mammalian mRNA transport system RNA localization controls spatial and temporal aspects of gene expression in a variety of species and cell types. Although its significance is better understood in specialized cells such as neurons, recent reports highlight its widespread prevalence, including in cells with a mesenchymal phenotype (Mardakheh et al, 2015;Wang et al, 2017;Fazal et al, 2019;Costa et al, 2020;Chouaib et al, 2020). Our current understanding of the transport mechanisms includes the requirement of cis-acting sequence elements and trans-acting factors, which work with the actin or microtubule networks and motor proteins to bring mRNAs to their destination (Cody et al, 2013;Medioni et al, 2012;Bovaird et al, 2018).…”

“…Apart from -actin, numerous other RNAs are localized at protrusions of mesenchymal cells and their local translation is important for cell migration (Mili et al, 2008;Mardakheh et al, 2015;Moissoglu et al, 2020;Costa et al, 2020). Localization of these RNAs is carried out through at least two distinct pathways.…”