Brenda E. Porter

Primary sequence of a motor neuron-selective adhesive site in the synaptic basal lamina protein s-laminin

S-laminin, a novel homolog of laminin, is concentrated in a subset of basal laminae including the basal lamina that passes between motor nerve terminals and muscle fibers at the neuromuscular junction. Here we used recombinant fragments to localize a neuronal attachment site to the C-terminal 10% of s-laminin. We then used synthetic peptides spanning the active fragment to identify the primary sequence of the adhesive site as Leu-Arg-Glu (LRE): neurons attach to an immobilized LRE-containing peptide, and soluble LRE blocks attachment of neurons to the s-laminin fragment. Whereas ciliary ganglion neurons (which normally innervate muscle fibers) adhered well both to laminin and to an s-laminin fragment, sensory and central neurons and several neuronal cell lines all adhered well to laminin but poorly to the s-laminin fragment. Together, these results define a motor neuron-selective attachment site on s-laminin.

Report of a parent survey of cannabidiol-enriched cannabis use in pediatric treatment-resistant epilepsy

Severe childhood epilepsies are characterized by frequent seizures, neurodevelopmental delays, and impaired quality of life. In these treatment-resistant epilepsies, families often seek alternative treatments. This survey explored the use of cannabidiol-enriched cannabis in children with treatment-resistant epilepsy. The survey was presented to parents belonging to a Facebook group dedicated to sharing information about the use of cannabidiol-enriched cannabis to treat their childs seizures. Nineteen responses met the following inclusion criteria for the study: a diagnosis of epilepsy and current use of cannabidiol-enriched cannabis. Thirteen children had Dravet syndrome, four had Doose syndrome, and one each had Lennox-Gastaut syndrome and idiopathic epilepsy. The average number of antiepileptic drugs (AEDs) tried before using cannabidiol-enriched cannabis was 12. Sixteen (84%) of the 19 parents reported a reduction in their childs seizure frequency while taking cannabidiol-enriched cannabis. Of these, two (11%) reported complete seizure freedom, eight (42%) reported a greater than 80% reduction in seizure frequency, and six (32%) reported a 25-60% seizure reduction. Other beneficial effects included increased alertness, better mood, and improved sleep. Side effects included drowsiness and fatigue. Our survey shows that parents are using cannabidiol-enriched cannabis as a treatment for their children with treatment-resistant epilepsy. Because of the increasing number of states that allow access to medical cannabis, its use will likely be a growing concern for the epilepsy community. Safety and tolerability data for cannabidiol-enriched cannabis use among children are not available. Objective measurements of a standardized preparation of pure cannabidiol are needed to determine whether it is safe, well tolerated, and efficacious at controlling seizures in this pediatric population with difficult-to-treat seizures.

A motoneuron-selective stop signal in the synaptic protein S-laminin

Motor axons preferentially reinnervate original synaptic sites on denervated muscle fibers. We have shown that components of synaptic basal lamina direct this selectivity, and we identified a protein, s-laminin, that is concentrated in synaptic basal lamina. Here, we report that a recombinant s-laminin fragment inhibits neurite outgrowth promoted by laminin. A tripeptide sequence in this fragment, Leu-Arg-Glu (LRE), contributes to this inhibition and is itself sufficient to inhibit outgrowth. LRE-mediated inhibition is selective for motoneuron-like cells and is observed in mixtures with several, but not all, outgrowth-promoting substrates. Growth cones extending on laminin stop for up to several hours upon contacting deposits of the s-laminin fragment. Thus, LRE may serve as a cell type-selective and context-dependent target-derived signal that plays a role in synapse formation.

Increased GABAA‐Receptor α1‐Subunit Expression in Hippocampal Dentate Gyrus after Early‐life Status Epilepticus

Summary:  Purpose: Previous studies in neonatal (postnatal day 10) and adult rats suggest that status epilepticus (SE) induces changes in the α1 subunit of the GABAA receptor (GABRA1) in dentate granule neurons (DGNs) that are age dependent and vary inversely with the likelihood of epilepsy development. In the present study, we examined GABRA1 expression after SE at postnatal day 20 (P20), an intermediate age when only a subset of SE‐exposed animals develop epilepsy.

Seizures and Antiepileptic Drugs: Does Exposure Alter Normal Brain Development?

Summary:  Seizures and antiepileptic drugs (AEDs) affect brain development and have long‐term neurological consequences. The specific molecular and cellular changes, the precise timing of their influence during brain development, and the full extent of the long‐term consequences of seizures and AEDs exposure have not been established. This review critically assesses both the basic and clinical science literature on the effects of seizures and AEDs on the developing brain and finds that evidence exists to support the hypothesis that both seizures and antiepileptic drugs influence a variety of biological process, at specific times during development, which alter long‐term cognition and epilepsy susceptibility. More research, both clinical and experimental, is needed before changes in current clinical practice, based on the scientific data, can be recommended.

Dysplasia: A common finding in intractable pediatric temporal lobe epilepsy

Background: Risk factors for temporal lobe epilepsy (TLE) include history of CNS infection, family history of epilepsy, and history of febrile convulsions (FC). Pre-existing cortical dysplasia (CD) may also predispose to refractory TLE, independent of other risk factors for epilepsy. Methods: The authors reviewed the neuropathologic features of surgical tissue from temporal lobectomies of 33 pediatric patients with refractory TLE, with and without a history of epilepsy risk factors. Results: CD was found in 64% (21/33) of all patients with refractory TLE, including 73% (11/15) patients with a history of FC, 66% (2/3) patients with CNS infections, and 83% (5/6) patients with a family history of epilepsy. Disrupted cortical lamination, dystrophic and maloriented neurons, and balloon cells characterized the CD found in the temporal neocortex. Conclusion: CD was seen in 21 of 33 surgical specimens from children with refractory TLE, including those with and without other epilepsy risk factors.Background Risk factors for temporal lobe epilepsy (TLE) include history of CNS infection, family history of epilepsy, and history of febrile convulsions (FC). Pre-existing cortical dysplasia (CD) may also predispose to refractory TLE, independent of other risk factors for epilepsy. Methods The authors reviewed the neuropathologic features of surgical tissue from temporal lobectomies of 33 pediatric patients with refractory TLE, with and without a history of epilepsy risk factors. Results CD was found in 64% (21/33) of all patients with refractory TLE, including 73% (11/15) patients with a history of FC, 66% (2/3) patients with CNS infections, and 83% (5/6) patients with a family history of epilepsy. Disrupted cortical lamination, dystrophic and maloriented neurons, and balloon cells characterized the CD found in the temporal neocortex. Conclusion CD was seen in 21 of 33 surgical specimens from children with refractory TLE, including those with and without other epilepsy risk factors.

The Perineuronal Net Component of the Extracellular Matrix in Plasticity and Epilepsy

During development the extracellular matrix (ECM) of the central nervous system (CNS) facilitates proliferation, migration, and synaptogenesis. In the mature nervous system due to changes in the ECM it provides structural stability and impedes proliferation, migration, and synaptogensis. The perineuronal net (PN) is a specialized ECM structure found primarily surrounding inhibitory interneurons where it forms a mesh-like structure around points of synaptic contact. The PN organizes the extracellular space by binding multiple components of the ECM and bringing them into close proximity to the cell membrane, forming dense aggregates surrounding synapses. The PN is expressed late in postnatal development when the nervous system is in the final stages of maturation and the critical periods are closing. Once fully expressed the PN envelopes synapses and leads to decreased plasticity and increases synaptic stability in the CNS. Disruptions in the PN have been studied in a number of disease states including epilepsy. Epilepsy is one of the most common neurologic disorders characterized by excessive neuronal activity which results in recurrent spontaneous seizures. A shift in the delicate balance between excitation and inhibition is believed to be one of the underlying mechanisms in the development of epilepsy. During epileptogenesis, the brain undergoes numerous changes including synaptic rearrangement and axonal sprouting, which require structural plasticity. Because of the PNs location around inhibitory cells and its role in limiting plasticity, the PN is an important candidate for altering the progression of epilepsy. In this review, an overview of the ECM and PN in the CNS will be presented with special emphasis on potential roles in epileptogenesis.

Distinct structures and functions of related pre- and postsynaptic carbohydrates at the mammalian neuromuscular junction.

Carbohydrates that terminate in beta-linked N-acetylgalactosamine (betaGalNAc) residues are concentrated in the postsynaptic apparatus of the skeletal neuromuscular junction and have been implicated in the differentiation of the postsynaptic membrane. We now report that distinct synapse-specific betaGalNAc-containing carbohydrates are associated with motor nerve terminals. Two monoclonal antibodies that recognize distinct betaGalNAc-containing epitopes, CT1 and CT2, both stain synaptic sites on skeletal muscle fibers. However, CT1 selectively stains nerve terminal, whereas CT2 selectively stains the postsynaptic apparatus. Likewise, CT1 and CT2 selectively stain motoneuron-like and muscle cell lines, respectively. Using the cell lines, we identify distinct CT1- and CT2-reactive glycolipids and glycoproteins. Finally, we show that GalNAc modulates the adhesion of motoneuron-like cells to recombinant fragments of a synaptic cleft component, laminin beta2. Together, these results show that pre- as well as postsynaptic membranes bear and are affected by distinct but related synapse-specific carbohydrates.

Changes in MicroRNA Expression in the Whole Hippocampus and Hippocampal Synaptoneurosome Fraction following Pilocarpine Induced Status Epilepticus

MicroRNAs regulate protein synthesis by binding non-translated regions of mRNAs and suppressing translation and/or increasing mRNA degradation. MicroRNAs play an important role in the nervous system including controlling synaptic plasticity. Their expression is altered in disease states including stroke, head injury and epilepsy. To better understand microRNA expression changes that might contribute to the development of epilepsy, microRNA arrays were performed on rat hippocampus 4 hours, 48 hours and 3 weeks following an episode of pilocarpine induced status epilepticus. Eighty microRNAs increased at one or more of the time points. No microRNAs decreased at 4 hours, and only a few decreased at 3 weeks, but 188 decreased 48 hours after status epilepticus. The large number of microRNAs with altered expression following status epilepticus suggests that microRNA regulation of translation has the potential to contribute to changes in protein expression during epileptogenesis. We carried out a second set of array’s comparing microRNA expression at 48 hours in synaptoneurosome and nuclear fractions of the hippocampus. In control rat hippocampi multiple microRNAs were enriched in the synaptoneurosomal fraction as compared to the nuclear fraction. In contrast, 48 hours after status epilepticus only one microRNA was enriched in the synaptoneurosome fraction. The loss of microRNAs enriched in the synaptoneurosomal fraction implies a dramatic change in translational regulation in synapses 48 hours after status epilepticus.

Interictal EEG spikes identify the region of electrographic seizure onset in some, but not all, pediatric epilepsy patients.

Purpose:  The role of sharps and spikes, interictal epileptiform discharges (IEDs), in guiding epilepsy surgery in children remains controversial, particularly with intracranial electroencephalography (IEEG). Although ictal recording is the mainstay of localizing epileptic networks for surgical resection, current practice dictates removing regions generating frequent IEDs if they are near the ictal onset zone. Indeed, past studies suggest an inconsistent relationship between IED and seizure‐onset location, although these studies were based upon relatively short EEG epochs.