Axon-specific mRNA translation shapes dopaminergic circuit development

The precise organization of midbrain dopaminergic (mDA) projections is essential for motor and cognitive functions, and their disruption contributes to multiple brain disorders. Yet the molecular mechanism guiding the development of these projections remains poorly defined. Here, we used ribosome tagging (RiboTag) and specific mouse crossing strategies (DATIRES-Cre mice) to isolate ribosome-bound mRNAs specifically from mDA axons and to analyze their axonal translatomes across developmental stages. We found that early-stage axons are enriched in transcripts involved in axon guidance and growth, while mature axons predominantly translate mRNAs related to synaptic function. Among key candidates, we identified PlxnA4, which is locally translated into mDA axons and modulates arborization in response to Sema3a. Functional assays in vitro and in vivo revealed that Plxna4-mediated signaling regulates topographical axon targeting and innervation, particularly in the nigrostriatal pathway. Our results uncover a dynamic and compartment-specific regulation of mRNA translation in developing mDA neurons, offering mechanistic insight into circuit formation and providing new molecular targets to improve integration of grafted neurons in regenerative therapies for Parkinsons disease.