Biology subjects

Balastik, M.

Publications and source records attributed to Balastik, M..

7 recordsLinked to original sources

bioRxiv2026

Reduced tubulin polyglutamylation perturbs neuronal function and causes late-onset neurodegeneration

Microtubules are essential for neuronal functions and are involved in many neurodegenerative disorders. A posttranslational modification (PTM) of neuronal microtubules, polyglutamylation, was shown to control cargo transport, Tau protein binding to microtubules and to induce early-onset neurodegeneration when exceeding physiological levels. To determine the physiological importance of this PTM, we characterised mouse models with reduced polyglutamylation. We demonstrate that these mice develop late-onset atrophy of the olfactory bulb and frontal cortex, progressively reduced dendritic spine density, and deficits in olfaction, memory, and cognitive control. This indicates an important role of polyglutamylation in neuronal function. To test whether the observed defects are linked to neurodegeneration, we combined mice with reduced polyglutamylation with a transgenic model for tauopathy. Strikingly, reduced polyglutamylation accelerated the premature demise of mice transgenic for human Tau carrying the P301S mutation. Our work thus reveals key roles of microtubule polyglutamylation in neuronal function with implications for late-onset neurodegeneration linked to Tau pathology.

neuroscience↗

bioRxiv2025

Interictal activity fluctuations follow rather than precede seizures on multiple time scales in a mouse model of focal cortical dysplasia

The unpredictability of seizure occurrence is a major debilitating factor for people with epilepsy. A seizure forecasting system would greatly improve their quality of life. Successful seizure forecasting necessitates a comprehensive understanding of the factors influencing seizure timing at multiple temporal scales. In this study, we investigated multiscale properties of interictal epileptiform discharges (IEDs) and seizure parameters in a highly realistic mouse model of focal cortical dysplasia-related epilepsy. We analyzed the properties evolution at four timescales, ranging from epilepsy progression and seizure clusters to circadian and peri-ictal changes. We discovered that the FCD-related epilepsy syndrome was progressive in terms of interictal activity rate and seizure characteristics. Sixty percent of seizures occurred in clusters. During the clusters, the seizure duration, seizure power, and IED rate were increasing. Circadian rhythm influenced seizure occurrence with the peak seizure probability at 4 p.m. under a standard 12/12 light dark cycle with lights-on at 6 a.m. Peri-ictal analysis revealed no significant change in IED rate preceding individual seizures; however, a consistent two-peak pattern of IED elevation was observed following seizures. Specifically, an initial peak in IED rate emerged 5-10 minutes post-seizure, returning to baseline within two hours, followed by a secondary peak 6-12 hours later, which again subsided to baseline levels in 24-48 hours. This pattern could be fitted with a sum of three exponentials. Using the three-exponential pattern, we simulated IED rate fluctuations in each animal. The smoothed simulated IED rates showed good agreement with the smoothed real recorded IED rates, suggesting that the cumulative effect of post-ictal IED patterns can account for long-term fluctuations in IED rate. Our results indicate that, in our model of FCD-related epilepsy, consistent IED rate fluctuations follow rather than precede individual seizures. Therefore, fluctuations in IED rate can be viewed as a reflection of cyclic seizure occurrence. This implies that either IED rate fluctuations or accurate seizure records may be equally valuable for seizure risk forecasting. HighlightsO_LIFCD-related epilepsy model displays a progressive nature and fluctuations between high and low seizure risk. C_LIO_LISeizures occur with higher probability in the day time which corresponds to sleep-related seizures commonly occurring in human patients with FCD. C_LIO_LIIED rate increases significantly after seizures, indicating a postictal effect rather than a preictal one, with the post-ictal phase displaying a two-peak pattern of fast and slow IED rate increase. C_LIO_LILong-term changes in the IED rate could be attributed to the time-dependent cumulative effect of the two-peak seizure-related increase in IED rate. C_LI

neuroscience↗

bioRxiv2025

Prolyl isomerase FKBP12 reduces axon growth and negatively regulates microtubule polymerization by inhibiting CRMP2A

Prolyl isomerases are enzymes catalyzing conformational change of the peptide bond between proline and the preceding amino acid, regulating the function and stability of their substrates. We have previously identified CRMP2A - the longer isoform of a microtubule-associated protein Collapsin response mediator protein 2 - as a substrate of the phospho-specific prolyl isomerase Pin1. CRMP2A is negatively regulated and destabilized by CDK5 phosphorylation in the distal axons and growth cones. Pin1 specifically binds to phosphorylated CRMP2A and stabilizes it by inducing conformational changes. However, the conformational regulation of unphosphorylated CRMP2 remains unknown. Here, we show that the prolyl isomerase FKBP12 specifically binds to unphosphorylated CRMP2A and regulates its activity. Using in vitro microtubule polymerization assays we demonstrate that CRMP2A promotes microtubule growth and that this function is inhibited by FKBP12. Next, using GFP-EB3 microtubule plus-end tracking assay, we demonstrate that FKBP12 inhibits CRMP2A-mediated microtubule polymerization also in cells. Furthermore, we show that FKBP12 co-localizes with unphosphorylated CRMP2A in growth cones and that expression of FKBP12 reduces axon growth in microfluidic chambers, while FKBP12 knockdown enhances it. Together, we demonstrate that FKBP12 is a negative regulator of microtubule dynamics and axon growth. Moreover, we show that two prolyl isomerases can differentially (positively or negatively) regulate activity of a common substrate depending on its phosphorylation. This provides an additional layer of phosphorylation-dependent or -independent control of protein activity, microtubule dynamics, and neuronal growth. Given the broad substrate specificity of FKBP12 and Pin1, this regulatory mechanism likely contributes to the modulation of diverse proteins and cellular processes in the nervous system and beyond.

neuroscience↗

bioRxiv2024

Tau phosphorylation impedes functionality of protective tau envelopes

Tau, an axonal microtubule-associated protein, is a critical regulator of microtubule function and stability. Tau interaction with microtubules is regulated by tau phosphorylation. Tau hyperphosphorylation is implicated in microtubule destabilization related to neurodegenerative disorders. How tau phosphorylation leads to microtubule destabilization is however unknown. Recently, it was shown that tau molecules on microtubules cooperatively assemble into cohesive layers termed envelopes. Tau envelopes protect microtubules against degradation by microtubule-severing enzymes, suggesting a functional link between envelopes and microtubule stability. Here we show that tau phosphorylation has deleterious effects on the microtubule-protective function of tau envelopes. Using reconstitution and live-cell experiments, we found that tau phosphorylation destabilizes tau envelopes and decreases their integrity, leading to reduced microtubule protection against microtubule-severing enzymes. Our data suggest that a perturbation of microtubule homeostasis linked to tau hyperphosphorylation in neurodegeneration, could be explained by the disassembly and impaired functionality of the tau envelopes.

cell biology↗

bioRxiv2024

Polyglutamylation of microtubules drives neuronal remodeling

Developmental remodeling shapes neural circuits via activity-dependent pruning of synapses and axons. The cytoskeleton is critical for this process, as microtubule loss via enzymatic severing is an early step of pruning across many circuits and species. However, how microtubule-severing enzymes, such as spastin, are activated in specific neuronal compartments remains unknown. Here, we reveal that polyglutamylation, a posttranslational tubulin modification that is enriched in neurons, plays an instructive role in developmental remodeling by tagging microtubules for severing. Motor neuron-specific gene deletion of enzymes that add or remove tubulin polyglutamylation--TTLL glutamylases vs. CCP deglutamylases--accelerates or delays neuromuscular synapse remodeling in a neurotransmission-dependent manner. This mechanism is not specific to peripheral synapses but also operates in central circuits, e.g., the hippocampus. Thus, tubulin polyglutamylation acts as an activity-dependent rheostat of remodeling and shapes neuronal morphology and connectivity.

cell biology↗

bioRxiv2019

Sema3A Facilitates a Retrograde Death Signal via CRMP4-Dynein Complex Formation in ALS Motor Axons

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease with selective dysfunction; it causes the death of motor neurons (MNs). In spite of some progress, currently no effective treatment is available for ALS. Before such treatment can be developed, a more thorough understanding of ALS pathogenesis is required. Recently, we demonstrated that ALS-mutated muscles contribute to ALS pathology via secretion of destabilizing factors such as Sema3A; these factors trigger axon degeneration and Neuromuscular Junction (NMJ) disruption. Here, we focus on the molecular mechanism by which muscle contribute to MNs loss in ALS. We identified CRMP4 as part of a retrograde death signal generated in response to muscle-secreted Sema3A, in ALS-diseased MNs. Exposing distal axons to Sema3A induces CRMP4-dynein complex formation and MN loss in both mouse (SOD1G93A) and human-derived (C9orf72) ALS models. Introducing peptides that interfere with CRMP4-dynein interaction in MN axons profoundly reduces Sema3A-dependent MN loss. Thus, we discovered a novel retrograde death signal mechanism underlying MN loss in ALS.\n\nSummaryMaimon et al. identify a novel retrograde death mechanism that contribute to MN loss in ALS, in which CRMP4-Dynein complex is form and retrogradely move along the axon.

neuroscience↗

bioRxiv2019

CRMP2 mediates Sema3F-dependent axon pruning and dendritic spine remodeling

Regulation of axon guidance and pruning of inappropriate synapses by class 3 semaphorins is key to development of neural circuits. Collapsin response mediator protein 2 (CRMP2) has been shown to regulate axon guidance by mediating Semaphorin 3A (Sema3A) signaling and its dysfunction has been linked to schizophrenia, however, nothing is known about its role in the synapse pruning. Here, using newly generated crmp2-/- mice we demonstrate that while CRMP2 has only a moderate effect on Sema3A-dependent axon guidance in vivo, it is essential for Sema3F-dependent axon pruning and dendritic spine remodeling. We first demonstrate that CRMP2 deficiency interferes with Sema3A signaling in compartmentalized neuron cultures and leads to a mild defect in axon guidance in peripheral nerves and corpus callosum. Strikingly, we show that crmp2-/- mice display more prominent defects in dendritic spine pruning and stereotyped axon pruning in hippocampus and visual cortex consistent with impaired Sema3F signaling and with autism spectrum disorder (ASD)-rather than schizophrenia-like phenotype. Indeed, we demonstrate that CRMP2 mediates Sema3F-induced axon retraction in primary neurons and that crmp2-/- mice display early postnatal behavioral changes linked to ASD. In conclusion, we demonstrate that CRMP2 is an essential mediator of Sema3F-dependent synapse pruning and its dysfunction in early postnatal stages shares histological and behavioral features of ASD.

neuroscience↗