Excitatory Synapse Scaffold Disruption Module

Module excitatory_synapse_scaffold_disruption 2 disorders Pathograph 5

A conserved neurodevelopmental mechanism module for disorders caused by disruption of postsynaptic-density (PSD) scaffold and scaffold-regulatory proteins at glutamatergic (excitatory) synapses. Loss of a core PSD organizer reduces structural organization of the excitatory postsynaptic compartment, perturbs AMPA/NMDA glutamate-receptor localization and trafficking, and impairs activity-dependent synaptic plasticity. The shared path is an altered excitatory/inhibitory (E/I) balance and aberrant cortical or cortico-striatal circuit assembly that manifests as autism spectrum disorder, intellectual disability, and/or epilepsy. This module is intended as a narrow first prototype for NEUROCIPHER-style circuit pathomechanism modeling (dismech#3549); it is scoped to postsynaptic excitatory-scaffold genes such as SHANK3 (PSD scaffold) and SYNGAP1 (postsynaptic Ras-GAP that maintains PSD architecture and AMPA-receptor trafficking), with DLG4/PSD-95 as a further candidate. It intentionally excludes presynaptic active-zone genes, inhibitory-interneuron channelopathies (e.g. SCN1A), and neuronal subtype-specification/migration disorders, which belong in separate circuit modules.

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Pathophysiology Nodes

5 shared nodes are defined in this module.

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Cell Types

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Biological Processes

Notes

This is a mechanism module, not a specific disease. Disorder entries should reference individual nodes via conforms_to using "excitatory_synapse_scaffold_disruption#<Node Name>". The generic cell type is glutamatergic neuron (CL:0000679); conforming entries substitute the disease-relevant subtype (e.g. cortical pyramidal neuron, medium spiny neuron). Module evidence reuses PMIDs already curated and cached in the conforming disorder entries; it is illustrative of the abstracted pattern rather than an exhaustive citation set. Circuit-level (anatomical location, synapse type, connectivity direction) claims are deliberately kept generic here and flagged as a knowledge gap pending schema follow-up.

Discussions and Knowledge Gaps

Disruption of distinct postsynaptic-density scaffold proteins (e.g. SHANK3, SYNGAP1) converges on a shared excitatory postsynaptic structural deficit and altered excitatory/inhibitory balance, yet the resulting clinical phenotype differs in emphasis (autism- and intellectual-disability-predominant for SHANK3 versus epilepsy-predominant for SYNGAP1). Which neuronal populations, cortical or cortico-striatal circuits, and developmental-timing windows determine whether a shared excitatory-scaffold lesion manifests primarily as autism/intellectual disability versus epilepsy?

KNOWLEDGE GAP OPEN gap_scaffold_phenotype_divergence

Attached to: Impaired Synaptic Plasticity and Excitatory-Inhibitory Imbalance Neurodevelopmental Phenotypic Output

The module abstracts a causal chain shared across excitatory-scaffold genes, but the biological basis for genotype-specific phenotypic divergence downstream of a common excitatory postsynaptic lesion is not established. Resolving which excitatory and inhibitory neuron populations and which circuits are differentially affected by each scaffold gene would clarify why the same mechanism produces autism-weighted versus epilepsy-weighted outcomes.

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Used By Disorder Entries

Epilepsy via SYNGAP1 Haploinsufficiency → Postsynaptic Scaffold Disruption , Postsynaptic Density Destabilization → Excitatory Postsynaptic Structural Deficit , Cortical Circuit Hard-Wiring → Circuit-Level Dysfunction

Phelan-McDermid Syndrome via SHANK3 haploinsufficiency → Postsynaptic Scaffold Disruption , Excitatory synapse structural deficit → Excitatory Postsynaptic Structural Deficit , Excitatory-inhibitory imbalance → Impaired Synaptic Plasticity and Excitatory-Inhibitory Imbalance

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Pathograph

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Pathophysiology

Postsynaptic Scaffold Disruption

trigger

The proximal molecular lesion: loss of function (typically haploinsufficiency) of a postsynaptic-density scaffold or scaffold-regulatory protein at glutamatergic synapses. These proteins organize the PSD and couple membrane glutamate receptors (NMDA, AMPA) to downstream signaling and the actin cytoskeleton. Conforming entries substitute the disease gene and its specific molecular role (structural scaffold for SHANK3; postsynaptic Ras-GAP that maintains PSD organization for SYNGAP1).

Glutamatergic neuron CL:0000679

Synapse assembly GO:0007416 Glutamate receptor signaling pathway GO:0007215

Used by disorders

Epilepsy as SYNGAP1 Haploinsufficiency

Phelan-McDermid Syndrome as SHANK3 haploinsufficiency

Downstream

Excitatory Postsynaptic Structural Deficit Loss of the PSD organizer degrades excitatory postsynaptic structure and receptor organization.

Excitatory Postsynaptic Structural Deficit

central effector

Disruption of the scaffold reduces structural organization and maturation of the excitatory postsynaptic compartment: fewer structurally mature glutamatergic synapses, destabilized PSD architecture, and impaired localization or trafficking of AMPA/NMDA-type glutamate receptors.

Glutamatergic neuron CL:0000679

Synapse assembly GO:0007416 DECREASED Postsynaptic density assembly GO:0097107 DECREASED

Used by disorders

Epilepsy as Postsynaptic Density Destabilization

Phelan-McDermid Syndrome as Excitatory synapse structural deficit

Downstream

Impaired Synaptic Plasticity and Excitatory-Inhibitory Imbalance Reduced excitatory synaptic structure lowers excitatory output and disrupts the E/I set point.

Impaired Synaptic Plasticity and Excitatory-Inhibitory Imbalance

central effector

Reduced excitatory glutamatergic transmission and impaired activity-dependent plasticity shift the balance between excitation and inhibition. In some genotypes the structural deficit selectively reduces excitatory (not inhibitory) transmission; in others, dysregulated signaling locks synaptic plasticity into an abnormal state. The shared consequence is an altered E/I balance at the synaptic level.

Glutamatergic neuron CL:0000679

Synaptic transmission, glutamatergic GO:0035249 DECREASED Regulation of synaptic plasticity GO:0048167 DECREASED

Used by disorders

Phelan-McDermid Syndrome as Excitatory-inhibitory imbalance

Downstream

Circuit-Level Dysfunction Synaptic-level E/I imbalance and plasticity deficits propagate to aberrant circuit assembly and dynamics.

Circuit-Level Dysfunction

consequence

Synaptic deficits aggregate into circuit-level pathology: aberrant cortical or cortico-striatal circuit assembly, abnormal connectivity and oscillatory dynamics, and network-level hyper- or hypo-excitability. The specific circuit and anatomical locus are disease-dependent (e.g. cortico-striatal circuits in SHANK3 models; cortical circuit consolidation in SYNGAP1).

Glutamatergic neuron CL:0000679

Regulation of synaptic plasticity GO:0048167 DECREASED

Used by disorders

Epilepsy as Cortical Circuit Hard-Wiring

Downstream

Neurodevelopmental Phenotypic Output Circuit dysfunction manifests as the neurodevelopmental and neuropsychiatric phenotype.

Neurodevelopmental Phenotypic Output

consequence

The clinical convergence point: excitatory-synapse scaffold disruption produces a neurodevelopmental phenotype spanning autism spectrum disorder, intellectual disability, developmental delay, and/or epilepsy. The relative weighting of features is genotype- and circuit-dependent.

Glutamatergic neuron CL:0000679