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.
Highlights
Dynamic subcellular polarisation of a myriad of proteins fundamentally shapes the front-rear orientation and directed movement of motile cells during tissue formation
We identified 233 transcripts enriched in fractionated cellular protrusions of migrating primary human umbilical vein endothelial cells (ECs) (HUVECs) in vitro (Fig 1A and B; Table EV1)
The motile protrusions and trailing cell bodies of ECs were separated and protrusion-enriched transcripts identified by RNAseq (Fig 1B; Table EV1). k-means clustering analysis of these data alongside RNAseq datasets from unrelated cell types (NIH/3T3 fibroblasts (Wang et al, 2017), MDA-MB231 metastatic breast cancer cells (Mardakheh et al, 2015), induced neuronal cells (Zappulo et al, 2017)) revealed unexpected cell typespecific diversity to transcript polarisation, with only five mRNAs exhibiting universal targeting to protrusions in all cell types tested
Summary
Dynamic subcellular polarisation of a myriad of proteins fundamentally shapes the front-rear orientation and directed movement of motile cells during tissue formation (reviewed in Mayor & EtienneManneville, 2016). In many other biological contexts, mRNA localisation and local translation are well-established as key determinants of cell polarity (Buxbaum et al, 2015). There is a wealth of data in diverse cell types demonstrating that large numbers of mRNAs are co-distributed together at distinct subcellular sites, which has led to the idea that such mRNA polarisation functions to generate local transcriptomes (reviewed in Engel et al, 2020). This suggests that clusters of mRNAs encoding proteins belonging to common complexes and biological pathways co-localise to participate in local processes (e.g. Mingle et al, 2005; Hotz & Nelson, 2017). During cell migration, the impact of mRNA polarisation on the control of translated protein function, local assembly of the migratory machinery and motile cell polarity remain poorly understood, as does the in vivo relevance of this phenomenon
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
