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Pacific salmon (Oncorhynchus spp.) rely on olfactory information learned in their natal rivers to guide their homing migration. Although molecules associated with synaptic plasticity show marked changes in the olfactory system during periods linked to imprinting, the contribution of brain-derived neurotrophic factor (BDNF/Bdnf), a key regulator of neural development and plasticity, has not been fully examined in salmonids. In this study, we isolated the complete coding sequence of masu salmon (O. masou) pro-bdnf and analyzed its expression profile across the olfactory system using wild individuals at multiple developmental stages. The deduced amino acid sequence of masu salmon pro-Bdnf was highly conserved among vertebrates. Pro-bdnf mRNA was strongly expressed in under-yearling parr prior to smoltification, particularly in the olfactory rosette and olfactory bulb at the sensitive period for imprinting. In the telencephalon, a higher olfactory center homologous to the mammalian cerebrum, pro-bdnf expression remained stable across stages, consistent with ongoing neurogenesis in this region. These results provide molecular evidence that pro-bdnf expression mirrors developmental changes in the olfactory system and support the idea that Bdnf contributes to the formation and refinement of olfactory circuits essential for imprinting and homing in Pacific salmon. Show less

The laminins are a family of extracellular matrix proteins that regulate numerous cellular processes, including adhesion, neurite outgrowth, and axon guidance. However, it remains unclear whether laminin regulates axon guidance through local translation. Here, we show that laminin is necessary for local translation in axonal growth cones. Local translation is significantly increased in growth cones of embryonic day 17 mouse cortical neurons, either cultured on or acutely stimulated with soluble laminin 111, in the presence of BDNF. When cultured on laminin isoforms 211 or 221 in the presence of BDNF, there was a remarkable decrease in local translation in growth cones. Using a puromycin-proximity ligation assay to examine newly synthesized β-actin specifically, we find a significant increase in growth cones of neurons cultured on laminin 111 in the presence of BDNF. However, soluble laminin 111 alone results in a significant reduction in nascent β-actin protein synthesis. These results indicate that laminin isoforms can act in multiple ways, including synergistically with guidance cues and independently, to modulate local mRNA translation, thereby differentially influencing axon growth and guidance during development. Local translation in axons is critical for axon guidance. Laminin, a key component of the extracellular matrix, is necessary to induce local translation and thus mediate axon growth and guidance. Show less

Axon growth is an essential cellular process during neural development, and its dysregulation contributes to numerous neurodevelopmental disorders. During axon growth, extracellular signals direct neurons to extend projections that connect with their synaptic targets. Paxillin is a key member of adhesion sites that control motility by linking the intracellular actin cytoskeleton to the extracellular matrix. Paxillin also binds to the cytoskeletal protein, tubulin. However, little is known about the role of adhesion proteins in neurons. Here, we use conditional paxillin knockout mice to investigate how loss of paxillin in pyramidal cortical neurons affects developing neuron morphology. Surprisingly, loss of paxillin in pyramidal cortical neurons caused no change in axon length or soma area between control ( Show less