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While interactions between neural crest and placode cells are critical for the proper formation of the trigeminal ganglion, the mechanisms underlying this process remain largely uncharacterized. Here, we show that the microRNA-(miR)203, whose epigenetic repression is required for neural crest migration, is reactivated in coalescing and condensing trigeminal ganglion cells. Overexpression of miR-203 induces ectopic coalescence of neural crest cells and increases ganglion size. Reciprocally, loss of miR-203 function in placode, but not neural crest, cells perturbs trigeminal ganglion condensation. Demonstrating intercellular communication, overexpression of miR-203 in the neural crestin vitroorin vivorepresses a miR-responsive sensor in placode cells. Moreover, neural crest-secreted extracellular vesicles (EVs), visualized using pHluorin-CD63 vector, become incorporated into the cytoplasm of placode cells. Finally, RT-PCR analysis shows that small EVs isolated from condensing trigeminal ganglia are selectively loaded with miR-203. Together, our findings reveal a critical role in vivo for neural crest-placode communication mediated by sEVs and their selective microRNA cargo for proper trigeminal ganglion formation.SIGNIFICANCE STRATEMENTCellular communication during early development plays a critical role. In this study, we demonstrate a unique role for a microRNA in cell-cell communication between the neural crest (NC) and placode cells (PC) during trigeminal ganglia (TG) formation. By utilizing loss and gain of function experiments in vivo, we demonstrate a requirement for miR-203 during cellular condensation to form the TG. We revealed that NC produces extracellular vesicles, selectively carrying miR-203, which is then taken up by the PC and regulates a sensor vector exclusively expressed in the placode. Taken together, our findings reveal a critical role in TG condensation for miR-203, produced by post-migratory NC and taken up by PC via extracellular vesicles.

Extracellular vesicles (EVs) are a unique and heterogeneous class of lipid bilayer nanoparticles secreted by most cells. EVs are regarded as important mediators of intercellular communication in both prokaryotic and eukaryotic cells due to their ability to transfer proteins, lipids and nucleic acids to recipient cells. In addition to their physiological role, EVs are recognized as modulators in pathological processes such as cancer, infectious diseases, and neurodegenerative disorders, providing new potential targets for diagnosis and therapeutic intervention. For a complete understanding of EVs as a universal cellular biological system and its translational applications, optimal techniques for their isolation and characterization are required. Here, we review recent progress in those techniques, from isolation methods to characterization techniques. With interest in therapeutic applications of EVs growing, we address fundamental points of EV‐related cell biology, such as cellular uptake mechanisms and their biodistribution in tissues as well as challenges to their application as drug carriers or biomarkers for less invasive diagnosis or as immunogens.This article is categorized under: Diagnostic Tools > BiosensingTherapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic DiseaseTherapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease