Year-end Sale % OFF 
Abstract
BackgroundAlthough neuronal extracellular sensing is emerging as crucial for brain wiring and therefore plasticity, little is known about these processes in neurodevelopmental disorders. Ubiquitin protein ligase E3A (UBE3A) plays a key role in neurodevelopment. Lack of UBE3A leads to Angelman syndrome (AS), while its increase is among the most prevalent genetic causes of autism (e.g., Dup15q syndrome). By using microstructured substrates that can induce specific directional stimuli in cells, we previously found deficient topographical contact guidance in AS neurons, which was linked to a dysregulated activation of the focal adhesion pathway.MethodsHere, we study axon and dendrite contact guidance and neuronal morphological features of wild-type, AS, and UBE3A-overexpressing neurons (Dup15q autism model) on micrograting substrates, with the aim to clarify the role of UBE3A in neuronal guidance.ResultsWe found that loss of axonal contact guidance is specific for AS neurons while UBE3A overexpression does not affect neuronal directional polarization along microgratings. Deficits at the level of axonal branching, growth cone orientation and actin fiber content, focal adhesion (FA) effectors, and actin fiber–binding proteins were observed in AS neurons. We tested different rescue strategies for restoring correct topographical guidance in AS neurons on microgratings, by either UBE3A protein re-expression or by pharmacological treatments acting on cytoskeleton contractility. Nocodazole, a drug that depolymerizes microtubules and increases cell contractility, rescued AS axonal alignment to the gratings by partially restoring focal adhesion pathway activation. Surprisingly, UBE3A re-expression only resulted in partial rescue of the phenotype.ConclusionsWe identified a specific in vitro deficit in axonal topographical guidance due selectively to the loss of UBE3A, and we further demonstrate that this defective guidance can be rescued to a certain extent by pharmacological or genetic treatment strategies. Overall, cytoskeleton dynamics emerge as important partners in UBE3A-mediated contact guidance responses. These results support the view that UBE3A-related deficits in early neuronal morphogenesis may lead to defective neuronal connectivity and plasticity.
Highlights
In the brain, neurons are embedded in a dense environment, the extracellular matrix (ECM), which contains a complex array of directional cues
Thanks to GRs, we showed for the first time the aberrant morphological phenotype of Angelman syndrome (AS) neurons in vitro: neurite contact guidance is defective in Ube3a-deficient hippocampal neurons at early stages of development (DIV1-3), and this phenotype is linked to an impaired activation of the focal adhesion (FA) signaling pathway [5]
Ubiquitin protein ligase E3A (UBE3A) unbalances role in axon and dendrite contact guidance In order to investigate the role of UBE3A in neuronal contact guidance and to explore neuronal morphological aspects relevant for its imbalance in AS and Dup15q autism, we exploited micrograting (GR) substrates with a grooved pattern of 1-μm ridge, 1-μm groove, and 500nm depth (Fig. 1a, b), which transfer a directional impulse to neuronal cells by contact interaction [5]
Summary
Neurons are embedded in a dense environment, the extracellular matrix (ECM), which contains a complex array of directional cues. Contact sensing triggers complex intracellular signaling patterns that are integrated by cells to guide neuronal adhesion, migration, neurite wiring, and synaptic plasticity [2, 3]. FAs act as sensors by integrating signals from both the ECM and chemotactic factors [3, 8] and mediate coordinated rearrangements of the cytoskeleton, essential for both neuronal growth and synaptic functionality [7]. Thereafter, neuronal growth and guidance to the proper targets require concerted efforts from the cytoskeleton (actin and microtubule) and from adhesions [10]. In this framework, the dilated tip of developing neurites, i.e., the growth cones (GCs), sense environmental cues leading the axons to their specific targets for precise neuronal wiring. By using microstructured substrates that can induce specific directional stimuli in cells, we previously found deficient topographical contact guidance in AS neurons, which was linked to a dysregulated activation of the focal adhesion pathway
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
