Biology subjects

Blanchette, C. R.

Publications and source records attributed to Blanchette, C. R..

4 recordsLinked to original sources

bioRxiv2026

Distinct Rab11-associated membrane trafficking pathways bidirectionally control neuronal extracellular vesicle cargo traffic

Neuronal extracellular vesicles (EVs) are released from synapses, and play roles in cellular communication, proteostasis, and the spread of toxic proteins in disease. The small GTPase Rab11 is required to maintain a reservoir of EV cargoes at presynaptic terminals, but how its diverse effector proteins contribute to this function and where Rab11 acts in neurons remains unclear. Using Drosophila motor neurons as a model, we show that EV cargoes redistribute from synapses to axons and cell bodies in rab11 mutants, concomitant with reduced release from synapses. We conducted a directed genetic screen of Rab11-associated factors and found that they have distinct roles in EV trafficking. Tethering and sorting factors are required to maintain levels of presynaptic EV precursors, supporting the hypothesis that Rab11 regulates EV cargo pools through recycling flux rather than by directly mediating EV release. Unexpectedly, we found that different classes of Rab11-associated proteins have opposite functions: the motor protein MyoV and the PI4KIII component Rbo sustain cargo levels at synapses, while the motor adaptor Nuf/Rab11FIP4 and the PI4KIII{beta} homolog Fwd restrict cargo levels. Together, these results indicate that Rab11 regulates multiple distinct organelle transport trajectories and PI(4)P populations to direct EV cargoes toward different cellular fates.

cell biology↗

bioRxiv2025

Remodeling of extracellular matrix collagen IV by MIG-6/papilin regulates neuronal architecture

Neuronal architecture established embryonically must persist lifelong to ensure normal brain function. However, little is understood about the mechanisms behind the long-term maintenance of neuronal organization. To uncover maintenance mechanisms, we performed a suppressor screen in sax-7/L1CAM mutants, which exhibit progressive disorganization with age. We identified the conserved extracellular matrix protein MIG-6/papilin as a key regulator of neuronal maintenance. Combining incisive molecular genetics, structural predictions, in vivo quantitative imaging, and cutting-edge Brillouin microscopy, we show that MIG-6/papilin remodels extracellular matrix collagen IV, working in concert with the secreted enzymes MIG-17/ADAMTS and PXN-2/peroxidasin. This remodeling impacts tissue biomechanics and ensures neuronal stability, even under increased mechanical stress. Our findings highlight an extracellular mechanism by which MIG-6/papilin supports the integrity of neuronal architecture throughout life. This work provides critical insights into the molecular basis of sustaining neuronal architecture and offers a foundation for understanding age-related and neurodegenerative disorders.

developmental biology↗

bioRxiv2021

Local regulation of extracellular vesicle traffic by the synaptic endocytic machinery

Neuronal extracellular vesicles (EVs) can be locally released from presynaptic terminals, carrying cargoes that are important in intercellular signaling and disease. EVs are derived from endosomes, but it remains unclear how synaptic cargoes are directed to the EV pathway, rather than undergoing conventional retrograde endosomal transport and degradation. Here, we find that the clathrin-mediated endocytic machinery plays an unexpected role in maintaining a release-competent pool of synaptic EV cargoes. Endocytic mutants, including nervous wreck (nwk), Shibire/Dynamin, and AP-2, exhibit local depletion of multiple cargoes in EV donor terminals. Accordingly, nwk mutants phenocopy synaptic plasticity defects associated with loss of the EV cargo Synaptotagmin-4, and suppress lethality upon overexpression of the EV cargo Amyloid Precursor Protein. These EV defects are genetically separable from canonical functions of endocytic proteins in synaptic vesicle recycling and synaptic growth. This endocytic pathway opposes the endosomal retromer complex to regulate EV cargo levels, and acts upstream of synaptic cargo removal by retrograde axonal transport. Our data suggest a novel molecular mechanism that protects EV cargoes from local depletion at synapses.

cell biology↗

bioRxiv2021

Neuronal post-developmentally acting SAX-7S/L1CAM can function as cleaved fragments to maintain neuronal architecture in C. elegans

Whereas remarkable advances have uncovered mechanisms that drive nervous system assembly, the processes responsible for the lifelong maintenance of nervous system architecture remain poorly understood. Subsequent to its establishment during embryogenesis, neuronal architecture is maintained throughout life in the face of the animals growth, maturation processes, the addition of new neurons, body movements, and aging. The C. elegans protein SAX-7, homologous to the vertebrate L1 protein family, is required for maintaining the organization of neuronal ganglia and fascicles after their successful initial embryonic development. To dissect the function of sax-7 in neuronal maintenance, we generated a null allele and sax-7S-isoform-specific alleles. We find that the null sax-7(qv30) is, in some contexts, more severe than previously described mutant alleles, and that the loss of sax-7S largely phenocopies the null, consistent with sax-7S being the key isoform in neuronal maintenance. Using a sfGFP::SAX-7S knock-in, we observe sax-7S to be predominantly expressed across the nervous system, from embryogenesis to adulthood. Yet, its role in maintaining neuronal organization is ensured by post-developmentally acting SAX-7S, as larval transgenic sax-7S(+) expression alone is sufficient to profoundly rescue the null mutants neuronal maintenance defects. Moreover, the majority of the protein SAX-7 appears to be cleaved, and we show that these cleaved SAX-7S fragments together, not individually, can fully support neuronal maintenance. These findings contribute to our understanding of the role of the conserved protein SAX-7/L1CAM in long-term neuronal maintenance, and may help decipher processes that go awry in some neurodegenerative conditions.

developmental biology↗