Alves Ferreira Dias, S. | bioRxiv Science

bioRxiv2026

In Vivo Massively Parallel Reporter Assay Reveals Sequence Determinants of mRNA Localization in Astrocytes

RNA localization and local translation are essential mechanisms to fine-tune spatiotemporal gene expression in the nervous system. However, efficiently assessing the thousands of possible sequence determinants of RNA localization is a challenge, particularly for cell types that only reach morphological maturity in vivo. Here, we developed an in vivo Massively Parallel Reporter Assay (MPRA), termed Synaptoneurosomal (SN)-MPRA to enable identification of sequence determinants of mRNA localization and local translation, and applied this to astrocytes. We evaluated multiple models of RNA localization for two locally translated astrocyte mRNAs, Glt1 and Sparc, including increased transcript abundance, "zipcode" elements, and RNA secondary structure. Our results establish a high-throughput in vivo framework for identifying cis-regulatory sequences driving RNA localization and local translation, and suggest astrocytes use diverse mechanisms to regulate subcellular gene expression. More broadly, SN-MPRA offers a versatile platform to study RNA localization in vivo, where biological context and intercellular interactions are preserved.

neuroscience↗

bioRxiv2026

Sex differences in exploration-exploitation strategies during home-cage decision making

The exploration-exploitation trade-off refers to the conflict between using known strategies that reliably yield reward (exploitation) and sampling uncertain options that might yield better outcomes (exploration). Dysregulation of this balance is implicated in neuropsychiatric disease, and while sex differences in this balance have been described, the biological bases remain unclear. To quantify sex differences in this trade-off, we tested mice (n=74 male, 62 female) on four home-cage based foraging tasks with an operant pellet dispensing device, Feeding Experimentation Device 3 (FED3). Mice completed the tasks continuously over multiple days and the tasks were their only source of food. Across multiple tasks, males showed higher win-stay behaviour than females, indicating greater exploitation of previously rewarded actions, an effect that was modest in size but highly significant. Power analyses revealed that >30 mice per sex were needed to detect these modest but significant sex differences with 80% power. No consistent sex differences were observed in pellet intake, suggesting that differences in exploitation did not reflect differences in hunger drive or demand for pellets. Exploitation is a more efficient strategy when environmental parameters are fixed, while exploration can be more advantageous when parameters such as reward locations are changing and uncertain. We tested this idea by re-running our mice in a probabilistic foraging task, where actions led to uncertain probabilities of reward. While males continued to show higher levels of win-stay behaviour on this task, this no longer led to increases in accuracy. Behavioural modelling also supported this framework, demonstrating that stronger win-stay behaviour was most advantageous in deterministic models, and less advantageous in probabilistic models. Together, our findings demonstrate that male and female mice have small but significant differences in their exploration-exploitation balance, which leads to more accurate foraging in certain, but not uncertain, environments.

neuroscience↗