Aavula, K. | bioRxiv Science

bioRxiv2025

Regulation of miR-219 and its target RalGPS dictates acute synaptic plasticity at the Drosophila neuromuscular junction

RNA regulatory mechanisms mediate adaptive responses requiring rapid gene expression changes. Examining microRNA (miRNA)-mediated control of structural synaptic plasticity, we identified miR-219 and six other conserved miRNAs regulating activity-induced morphogenesis at Drosophila glutamatergic synapses. Among miRNA targets downregulated by acute stimulation, the Ral-activating factor RalGPS is necessary for presynaptic morphogenesis and sufficient to block plasticity. Stimulation elevates miR-219 loading into Argonaute complexes without altering mature miR-219 levels, revealing a post-transcriptional regulatory mechanism. We conclude that activity-induced miRNA loading modulates Ral signaling via RalGPS to enable presynaptic remodeling and growth, establishing a novel link between neuronal activity and synaptic structural plasticity.

neuroscience↗

bioRxiv2025

Protein phosphatase 4 is required for centrosome asymmetry in fly neural stem cells

Asymmetric cell division is used by stem cells to create diverse cell types while self-renewing the stem cell population. Biased segregation of molecularly distinct centrosomes could provide a mechanism to maintain stem cell fate, induce cell differentiation or both. However, the molecular mechanisms generating molecular and functional asymmetric centrosomes remain incompletely understood. Here, we show that in asymmetrically dividing fly neural stem cells, Protein phosphatase 4 (Pp4) is necessary for correct centrosome asymmetry establishment during mitosis, and microtubule organizing center (MTOC) maintenance in interphase. Using in-vivo live cell imaging we show that while wild type neural stem cells always maintain one active MTOC, Pp4 mutant neuroblasts contain two inactive centrioles in interphase. Furthermore, centrosomes of Pp4 mutant neural stem cells mature in mitosis but fail to correctly transfer the centriolar protein Centrobin (Cnb) from the mother to the daughter centriole. Using superresolution imaging, we find that phosphomimetic Centrobin fails to accurately relocalize in mitosis. We propose that Pp4 regulates the timely relocalization of Cnb in mitosis to establish two molecularly distinct centrosomes. In addition, Pp4 is also necessary to maintain MTOC activity in interphase, ensuring biased centrosome segregation. Mechanistically, Pp4 could regulate centrosome asymmetry by dephosphorylating both Cnb and gamma-Tubulin. SIGNIFICANCE STATEMENTO_LIAsymmetric centrosome segregation occurs in stem cells and has been linked with cell fate decisions. C_LIO_LIProtein phosphatase 4 (Pp4), a conserved Serine/Threonine phosphatase, regulates centrosome asymmetry in Drosophila neural stem cells by acting upon gamma tubulin and Centrobin. C_LIO_LIPp4 regulates centrosome asymmetry establishment in mitosis and interphase, necessary for biased centrosome segregation. C_LI

cell biology↗