Mossy Fiber Synaptic Reorganization in Temporal Lobe Epilepsy

Temporal lobe epilepsy is often accompanied by profound remodelling of the hippocampal dentate gyrus, wherein the granule cell axons—known as mossy fibres—elaborate aberrant collaterals into the inner molecular layer. This phenomenon, termed mossy fibre sprouting, establishes recurrent excitatory circuits that contribute to network hyperexcitability and seizure generation. Associated morphological hallmarks include loss of hilar interneurons and degeneration in CA1, facilitating the emergence of novel synaptic contacts onto granule cells and, in some cases, onto neighbouring pyramidal neurons. At the molecular level, guidance cues, cell adhesion molecules and intracellular regulators orchestrate axonal branching and target selection in the adult brain, revealing unexpected plasticity beyond developmental stages. These structural changes not only underpin epileptogenesis but also offer windows into mechanisms of circuit rewiring relevant to regenerative therapies. Understanding how specific signalling pathways control sprouting and synaptic specificity provides avenues for interventions aimed at preventing recurrent seizure activity and restoring circuit integrity.

Research from Nature Portfolio

Computational modelling of the dentate circuitry has elucidated the role of GABAa receptor–mediated excitation in promoting mossy fibre sprouting following status epilepticus. Simulations incorporating non-synaptic ionic homeostasis and Hebbian plasticity rules reproduced ictal discharges and predicted that depolarising GABAa action enhances aberrant collateral growth. The model further indicates a compensatory reduction of mossy cell connectivity and increased interneuron inhibition, suggesting a network-level response that paradoxically amplifies epileptiform activity. These insights offer a framework for targeting GABAergic signalling in disease-modifying strategies.

Mossy Fiber Synaptic Reorganization in Temporal Lobe Epilepsy publication trend

The graph below shows the total number of articles in mossy fiber synaptic reorganization in temporal lobe epilepsy across all publications each year (not limited to Nature Index journals).

Technical terms

Mossy fibre sprouting: The growth of new granule cell axon collaterals into the inner molecular layer of the dentate gyrus, forming recurrent excitatory loops.

Dentate gyrus: A hippocampal subregion containing granule cells whose axons are termed mossy fibres.

Hebbian plasticity: A synaptic modification rule in which co-active pre- and postsynaptic neurons strengthen their connection.

Semaphorin3F–Neuropilin-2 signalling: A guidance cue pathway that regulates axon growth and branching through intracellular effectors such as CRMP2.

Protocadherin-11 X-linked (Pcdh11x): A cell adhesion molecule that determines synaptic target specificity during neural circuit formation.

Kainate receptor: A subtype of ionotropic glutamate receptor that modulates neuronal excitability and network synchrony.

References

1. Is Mossy Fiber Sprouting a Potential Therapeutic Target for Epilepsy?. Frontiers in Neurology (2018).
2. The Molecular and Cellular Mechanisms of Axon Guidance in Mossy Fiber Sprouting. Frontiers in Neurology (2018).
3. Neuropilin-2 Signaling Modulates Mossy Fiber Sprouting by Regulating Axon Collateral Formation Through CRMP2 in a Rat Model of Epilepsy. Molecular Neurobiology (2022).
4. Pcdh11x controls target specification of mossy fiber sprouting. Frontiers in Neuroscience (2022).
5. Kainate receptors modulate the microstructure of synchrony during dentate gyrus epileptiform activity. Neurobiology of Disease (2023).
6. GABAa excitation and synaptogenesis after Status Epilepticus – A computational study. Scientific Reports (2018).