Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2025.08.01.668222

Shank3 establishes AMPA receptor subunit composition at cerebellar mossy fiber-granule cell synapses and shapes regional microglia activation.

Kshetri, R.·Richardson, B. D.
View original source ↗Export metadata ↓

Abstract

Mutations in Shank3 are the primary genetic cause of Phelan-McDermid Syndrome (PMS), a neurodevelopmental disorder frequently comorbid with autism spectrum disorder (ASD). As a key scaffolding protein in the postsynaptic site, SHANK3 is critical for excitatory glutamatergic synapse function by interacting with AMPARs, NMDARs, and mGluRs. While Shank3 deficiency has been extensively studied in forebrain regions, its role in the cerebellum, a brain area increasingly implicated in ASD pathobiology, remains comparatively underexplored. Cerebellar granule cells (CGCs) exhibit high Shank3 expression. However, its role in cerebellar glutamatergic synapses is poorly understood. This study aims to investigate how Shank3 loss affects mossy fiber-CGC glutamatergic synaptic function. Whole-cell patch clamp electrophysiological recordings from CGCs in ex vivo cerebellar brain slices from adult (4-6 months old) wild type (WT) and homozygous Shank3{Delta}ex4-22 KO were performed to record miniature, evoked, and glutamate uncaged responses. Similarly, the current-voltage (I-V) relationship was analyzed with intracellular spermine and pharmacological validation of calcium-permeable AMPARs (CP-AMPARs) was done by IEM-1460. Immunofluorescence staining was performed for microglia using IBA1 labeling. We found a significant increase in mEPSC amplitude and AMPAR-mediated response to glutamate uncaging, which indicates that the loss of Shank3 enhances postsynaptic AMPAR function. Furthermore, the KO group showed faster AMPAR decay kinetics, inward rectification, and increased sensitivity to IEM-1460, suggesting that a high proportion of CP-AMPARs with distinct biophysical properties are present at the MF-CGC synapse. Furthermore, KO mice showed less ramified microglia suggesting the possible presence of activated microglia in the cerebellar cortex. Together, these findings highlight a critical role of Shank3 in maintaining the balance between CP- and CI-AMPARs at the MF-CGC synapse, which is essential for synapse maturation and proper cerebellar circuitry function. Dysregulation of this balance, with possible presence of activated microglia in the cerebellum, may underscore cerebellar-related behavioral deficits in Shank3 KO mice and may suggest a potential mechanism contributing to ASD pathophysiology.

Explore related subjects

neurosciencePreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Kshetri, R., Richardson, B. D.. 2025-08-01. Shank3 establishes AMPA receptor subunit composition at cerebellar mossy fiber-granule cell synapses and shapes regional microglia activation.. https://doi.org/10.1101/2025.08.01.668222

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Same Movements, Different Skills: How Context Shapes Learning in Humans and Neural Networks

What determines whether experiences are integrated into shared representations or split? Motor skill learning offers a revealing test: when two tasks require an identical sequence of movements, both intuition and theory suggest that practice in one should generalize to the other. Yet we find that changing context can make identical movements different skills. In simple recurrent networks trained on the same sequence across contexts, splitting was greatest when strong contextual inputs coincided with a high initial weight scale; neither alone sufficed. Greater representational separation coincided with separate context-specific learning curves. Humans practicing the same finger sequence while alternating between two performance-irrelevant contexts likewise exhibited context-specific curves, rather than the single continuous trajectory observed when practicing in a single context. State-space modeling favored split learning states in humans and very weakly coupled states in the most context-dependent networks. These findings have broader implications for understanding how learning generalizes across contexts.

neuroscience↗
bioRxiv2026

Postpartum resource scarcity reshapes maternal care, offspring prioritization, and the steroid-sensitive medial preoptic area

Parental care requires balancing offspring needs with environmental constraints, yet how resource scarcity alters the organization of maternal responses remains poorly understood. Here, we examined maternal behavior, offspring prioritization, and steroid receptor-associated extracellular matrix organization in postpartum rats exposed to limited bedding and nesting (LBN) or control conditions with ample nesting materials. LBN increased pup-directed and reduced self-directed behaviors but also increased behavioral entropy, a measure of behavioral fragmentation, indicating less predictable caregiving sequences. LBN dams preferentially retrieved male pups first, whereas control dams preferentially retrieved females first. LBN also increased the proportion of pup-investigation time directed toward males compared with controls. In offspring on postnatal day 10, corticosterone was elevated in female but not male LBN pups, a pattern that paralleled the maternal male bias. To identify associated neurobiological changes, we assessed steroid receptors and extracellular matrix organization in the medial preoptic area (mPOA), a key region for maternal behavior. LBN increased numbers of estrogen receptor (ER)- and androgen receptor (AR)-immunoreactive cells, reduced perineuronal net (PNN) abundance, and decreased receptor-positive cell enwrapment. Because PNNs constrain structural plasticity, these findings suggest that the postpartum environment alters the organization of steroid receptor-associated extracellular matrix, potentially modulating experience-dependent plasticity in neurosteroid-sensitive circuits. In sum, LBN increases the levels of maternal engagement while reshaping its temporal organization and allocation, accompanied by selective remodeling of steroid-sensitive preoptic architecture. Therefore, maternal adaptation to adversity may be better understood as changes in caregiving allocation strategies rather than a simple gain or loss of maternal care.

neuroscience↗
bioRxiv2026

The Computational Grammar of Human Behaviour in a Biological Environment

Human behaviour unfolds as an extended stream of spontaneous actions shaped by environmental demands and the agent's goals. The organisation of these actions, situated between setting abstract goals and concrete movement execution, remains poorly characterised. Here, we introduce DynaClade, an unsupervised temporal action segmentation algorithm for human full-body motion capture data, and apply it to freely moving participants navigating ecologically realistic risky foraging environments in virtual reality. DynaClade identifies discrete actions whose kinematic characteristics and spatial distributions correspond to environmental affordances, supporting the validity of the approach. Among these actions, we discovered a hitherto undescribed movement pattern defined by increased body sway without locomotion. Action sequences were highly non-random and showed clear history dependence beyond first-order Markov structure, most of which was explained by a second-order prediction. This higher-order structure was well captured in a hidden Markov model, in which some of the observed actions were associated with more than one latent state. Each of these latent states corresponded to the same action in a distinct action context. These findings suggest that spontaneous human actions are predominantly selected based on the current action and context, rather than following pre-planned or habitually assembled sequences.

neuroscience↗