- Neurology - Child Neurology
Residency:Hospital of the University of Pennsylvania (2000) PA
Residency:St Louis Childrens Hospital (1997) MO
Internship:St Louis Childrens Hospital (1996) MO
Board Certification: Clinical Neurophysiology, American Board of Psychiatry and Neurology (2003)
Board Certification: Neurology - Child Neurology, American Board of Psychiatry and Neurology (2002)
Fellowship:The Children's Hospital of Philadelphia (2002) PA
Medical Education:Washington Univ School Of Med (1995) MO
MD,PhD, Washington University School of Medicine, Neurobiology and Medicine (1995)
Preventing Epilepsy Using Vigabatrin In Infants With Tuberous Sclerosis Complex
Study design is a Phase IIb prospective multi-center, randomized, placebo-controlled, double-blind clinical trial. The goal will be to enroll 80 infants with Tuberous Sclerosis Complex who are less than 6 months of age prior to the onset of their first seizure
Stanford is currently not accepting patients for this trial. For more information, please contact Spectrum Child Health, 650-724-1175.
Increased precursor microRNA-21 following status epilepticus can compete with mature microRNA-21 to alter translation.
2016; 286: 137-146
MicroRNA-21 (miR-21) is consistently up-regulated in various neurological disorders, including epilepsy. Here, we show that the biogenesis of miR-21 is altered following pilocarpine-induced status epilepticus (SE) with an increase in precursor miR-21 (pre-miR-21) in rats. We demonstrate that pre-miR-21 has an energetically favorable site overlapping with the miR-21 binding site and competes with mature miR-21 for binding in the 3'UTR of TGFBR2 mRNA, but not NT-3 mRNA in vitro. This binding competition influences miR-21-mediated repression in vitro and correlates with the increase in TGFBR2 and decrease in NT-3 following SE. Polysome profiling reveals co-localization of pre-miR-21 in the ribosome fraction with translating mRNAs in U-87 cells. The current work suggests that pre-miR-21 may post-transcriptionally counteract miR-21-mediated suppression following SE and could potentially lead to prolonged TGF-β receptor expression impacting epileptogenesis. The study further supports that the ratio of the pre to mature miRNA may be important in determining the regulatory effects of a miRNA gene.
View details for DOI 10.1016/j.expneurol.2016.10.003
View details for PubMedID 27725160
Diagnosis of adenylosuccinate lyase deficiency by metabolomic profiling in plasma reveals a phenotypic spectrum.
Molecular genetics and metabolism reports
2016; 8: 61-66
Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive neurometabolic disorder that presents with a broad-spectrum of neurological and physiological symptoms. The ADSL gene produces an enzyme with binary molecular roles in de novo purine synthesis and purine nucleotide recycling. The biochemical phenotype of ADSL deficiency, accumulation of SAICAr and succinyladenosine (S-Ado) in biofluids of affected individuals, serves as the traditional target for diagnosis with targeted quantitative urine purine analysis employed as the predominate method of detection. In this study, we report the diagnosis of ADSL deficiency using an alternative method, untargeted metabolomic profiling, an analytical scheme capable of generating semi-quantitative z-score values for over 1000 unique compounds in a single analysis of a specimen. Using this method to analyze plasma, we diagnosed ADSL deficiency in four patients and confirmed these findings with targeted quantitative biochemical analysis and molecular genetic testing. ADSL deficiency is part of a large a group of neurometabolic disorders, with a wide range of severity and sharing a broad differential diagnosis. This phenotypic similarity among these many inborn errors of metabolism (IEMs) has classically stood as a hurdle in their initial diagnosis and subsequent treatment. The findings presented here demonstrate the clinical utility of metabolomic profiling in the diagnosis of ADSL deficiency and highlights the potential of this technology in the diagnostic evaluation of individuals with neurologic phenotypes.
View details for DOI 10.1016/j.ymgmr.2016.07.007
View details for PubMedID 27504266
A Potential Role for Glia-Derived Extracellular Matrix Remodeling in Postinjury Epilepsy
JOURNAL OF NEUROSCIENCE RESEARCH
2016; 94 (9): 794-803
Head trauma and vascular injuries are known risk factors for acquired epilepsy. The sequence of events that lead from the initial injury to the development of epilepsy involves complex plastic changes and circuit rewiring. In-depth, comprehensive understanding of the epileptogenic process is critical for the identification of disease-modifying targets. Here we review the complex interactions of cellular and extracellular components that may promote epileptogenesis, with an emphasis on the role of astrocytes. Emerging evidence demonstrates that astrocytes promptly respond to brain damage and play a critical role in the development of postinjury epilepsy. Astrocytes have been shown to regulate extracellular matrix (ECM) remodeling, which can affect plasticity and stability of synapses and, in turn, contribute to the epileptogenic process. From these separate lines of evidence, we present a hypothesis suggesting a possible role for astrocyte-regulated remodeling of ECM and perineuronal nets, a specialized ECM structure around fast-spiking inhibitory interneurons, in the development and progression of posttraumatic epilepsies. © 2016 Wiley Periodicals, Inc.
View details for DOI 10.1002/jnr.23758
View details for Web of Science ID 000383282900003
View details for PubMedID 27265805
Plasma taurine levels are not affected by vigabatrin in pediatric patients.
2016; 57 (8): e168-72
Vigabatrin is a highly effective antiseizure medication, but its use is limited due to concerns about retinal toxicity. One proposed mechanism for this toxicity is vigabatrin-mediated reduction of taurine. Herein we assess plasma taurine levels in a retrospective cohort of children with epilepsy, including a subset receiving vigabatrin. All children who underwent a plasma amino acid analysis as part of their clinical evaluation between 2006 and 2015 at Stanford Children's Health were included in the analysis. There were no significant differences in plasma taurine levels between children taking vigabatrin (n = 16), children taking other anti-seizure medications, and children not taking any anti-seizure medication (n = 556) (analysis of variance [ANOVA] p = 0.841). There were, however, age-dependent decreases in plasma taurine levels. Multiple linear regression revealed no significant association between vigabatrin use and plasma taurine level (p = 0.87) when controlling for age. These results suggest that children taking vigabatrin maintain normal plasma taurine levels, although they leave unanswered whether taurine supplementation is necessary or sufficient to prevent vigabatrin-associated visual field loss. They also indicate that age should be taken into consideration when evaluating taurine levels in young children.
View details for DOI 10.1111/epi.13447
View details for PubMedID 27344989
Mutations in the Na(+)/citrate cotransporter NaCT (SLC13A5) in pediatric patients with epilepsy and developmental delay.
Mutations in the SLC13A5 gene that codes for the Na(+)/citrate cotransporter, NaCT, are associated with early onset epilepsy, developmental delay and tooth dysplasia in children. In the present study we identify additional SLC13A5 mutations in nine epilepsy patients from six families. To better characterize the syndrome, families with affected children answered questions about the scope of illness and treatment strategies. There are currently no effective treatments, but some anti-epileptic drugs targeting the GABA system reduce seizure frequency. Acetazolamide, a carbonic anhydrase inhibitor and atypical anti-seizure medication decreases seizures in 4 patients. In contrast to previous reports, the ketogenic diet and fasting produce worsening of symptoms. The effects of the mutations on NaCT transport function and protein expression were examined by transient transfections of COS-7 cells. There was no transport activity from any of the mutant transporters, although some of the mutant transporter proteins were present on the plasma membrane. The structural model of NaCT suggests that these mutations can affect helix packing or substrate binding. We tested various treatments, including chemical chaperones and low temperatures, but none improve transport function in the NaCT mutants. Interestingly, coexpression of NaCT and the mutants results in decreased protein expression and activity of the wild-type transporter, indicating functional interaction. In conclusion, our study has identified additional SLC13A5 mutations in patients with chronic epilepsy starting in the neonatal period, with the mutations producing inactive Na(+)/citrate transporters.
View details for DOI 10.2119/molmed.2016.00077
View details for PubMedID 27261973
Perineuronal net degradation in epilepsy
2015; 56 (7): 1124-1133
We previously reported loss of perineuronal net (PN) immunohistochemical staining around parvalbumin-positive interneurons in the hippocampus of rats after an episode of status epilepticus (SE). We hypothesized that the loss of the PN could alter seizure susceptibility and that matrix metalloproteinases (MMPs) were candidates for degradation of the PN following SE.The pilocarpine chemoconvulsant rodent epilepsy model was used to characterize the degradation of the aggrecan component of the PN in the hippocampus following SE. Chondroitinase ABC (ChABC) was used to degrade the PN in mice. Onset, number, and duration of pentylenetetrazole (PTZ)-induced seizures were assessed.The loss of the PN in the hippocampus following SE is at least partially related to degradation of the aggrecan PN component by MMP activity. Forty-eight hours after SE, a neoepitope created by MMP cleavage of aggrecan was present and concentrated around parvalbumin-positive interneurons. The increase in aggrecan cleavage products was found at 48 h, 1 week, and 2 months after SE, with different fragments predominating over time. We demonstrate ongoing aggrecan proteolysis and fragment accumulation in the hippocampus of adult control rats, as well as in SE-treated animals. Degradation of the PN alters the seizure response to PTZ. ChABC treatment caused an increase in myoclonic seizures following PTZ administration, a delayed onset of Racine stage 4/5 seizure, and a decreased duration of Racine stage 4/5 seizure.Status epilepticus increases MMP proteolysis of aggrecan, pointing to MMP activity as one mechanism of PN degradation post-SE. There is accumulation of aggrecan fragments in adult rat hippocampus of both control and SE-exposed animals. Loss of the PN was associated with increased numbers of myoclonic seizures; it also, delayed and shortened the duration of Racine stage 4/5 seizures, suggesting a complex relationship between the PN and seizure susceptibility.
View details for DOI 10.1111/epi.13026
View details for Web of Science ID 000357728400020
- 50 years ago in the journal of pediatrics: convulsive equivalent syndrome of childhood. journal of pediatrics 2014; 164 (5): 1050-?
Report of a parent survey of cannabidiol-enriched cannabis use in pediatric treatment-resistant epilepsy
EPILEPSY & BEHAVIOR
2013; 29 (3): 574-577
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 child's 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 child's 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.
View details for DOI 10.1016/j.yebeh.2013.08.037
View details for Web of Science ID 000327188200026
View details for PubMedID 24237632
MEF2C Haploinsufficiency features consistent hyperkinesis, variable epilepsy, and has a role in dorsal and ventral neuronal developmental pathways
2013; 14 (2): 99-111
MEF2C haploinsufficiency syndrome is an emerging neurodevelopmental disorder associated with intellectual disability, autistic features, epilepsy, and abnormal movements. We report 16 new patients with MEF2C haploinsufficiency, including the oldest reported patient with MEF2C deletion at 5q14.3. We detail the neurobehavioral phenotype, epilepsy, and abnormal movements, and compare our subjects with those previously reported in the literature. We also investigate Mef2c expression in the developing mouse forebrain. A spectrum of neurofunctional deficits emerges, with hyperkinesis a consistent finding. Epilepsy varied from absent to severe, and included intractable myoclonic seizures and infantile spasms. Subjects with partial MEF2C deletion were statistically less likely to have epilepsy. Finally, we confirm that Mef2c is present both in dorsal primary neuroblasts and ventral gamma-aminobutyric acid(GABA)ergic interneurons in the forebrain of the developing mouse. Given interactions with several key neurodevelopmental genes such as ARX, FMR1, MECP2, and TBR1, it appears that MEF2C plays a role in several developmental stages of both dorsal and ventral neuronal cell types.
View details for DOI 10.1007/s10048-013-0356-y
View details for Web of Science ID 000318881100002
View details for PubMedID 23389741
Focal cortical dysplasia is more common in boys than in girls
EPILEPSY & BEHAVIOR
2013; 27 (1): 121-123
Genetics and environment likely contribute to the development of medically intractable epilepsy; however, in most patients the specific combination of etiologies remains unknown. Here, we undertook a multicenter retrospective cohort study of sex distribution in pediatric patients undergoing epilepsy surgery and carried out a secondary analysis of the same population subdivided by histopathologic diagnosis. In the multicenter cohort of patients with intractable epilepsy undergoing surgery regardless of etiology (n=206), 63% were boys, which is significantly more boys than expected for the general population (Fisher exact two-tailed p=0.017). Subgroup analysis found that of the 90 patients with a histopathologic diagnosis of focal cortical dysplasia, 72% were boys, giving an odds ratio (OR) of 2.5 (95% CI, 1.34 to 4.62) for male sex. None of the other etiologies had a male sex predominance. Future studies could examine the biological relevance and potential genetic and pathophysiological mechanisms of this observation.
View details for DOI 10.1016/j.yebeh.2012.12.035
View details for Web of Science ID 000317029000022
View details for PubMedID 23416281
Changes in MicroRNA Expression in the Whole Hippocampus and Hippocampal Synaptoneurosome Fraction following Pilocarpine Induced Status Epilepticus
2013; 8 (1)
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.
View details for DOI 10.1371/journal.pone.0053464
View details for Web of Science ID 000313429100071
View details for PubMedID 23308228
Persistent decrease in multiple components of the perineuronal net following status epilepticus
EUROPEAN JOURNAL OF NEUROSCIENCE
2012; 36 (11): 3471-3482
In the rodent model of temporal lobe epilepsy, there is extensive synaptic reorganization within the hippocampus following a single prolonged seizure event, after which animals eventually develop epilepsy. The perineuronal net (PN), a component of the neural extracellular matrix (ECM), primarily surrounds inhibitory interneurons and, under normal conditions, restricts synaptic reorganization. The objective of the current study was to explore the effects of status epilepticus (SE) on PNs in the adult hippocampus. The aggrecan component of the PN was studied, acutely (48 h post-SE), sub-acutely (1 week post-SE) and during the chronic period (2 months post-SE). Aggrecan expressing PNs decreased by 1 week, likely contributing to a permissive environment for neuronal reorganization, and remained attenuated at 2 months. The SE-exposed hippocampus showed many PNs with poor structural integrity, a condition rarely seen in controls. Additionally, the decrease in the aggrecan component of the PN was preceded by a decrease in hyaluronan and proteoglycan link protein 1 (HAPLN1) and hyaluronan synthase 3 (HAS3), which are components of the PN known to stabilize the connection between aggrecan and hyaluronan, a major constituent of the ECM. These results were replicated in vitro with the addition of excess KCl to hippocampal cultures. Enhanced neuronal activity caused a decrease in aggrecan, HAPLN1 and HAS3 around hippocampal cells in vivo and in vitro, leaving inhibitory interneurons susceptible to increased synaptic reorganization. These studies are the foundation for future experiments to explore how loss of the PN following SE contributes to the development of epilepsy.
View details for DOI 10.1111/j.1460-9568.2012.08268.x
View details for Web of Science ID 000312156700002
View details for PubMedID 22934955
The perineuronal net component of the extracellular matrix in plasticity and epilepsy
2012; 61 (7): 963-972
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.
View details for DOI 10.1016/j.neuint.2012.08.007
View details for Web of Science ID 000314616400002
View details for PubMedID 22954428
Decreased CREB levels suppress epilepsy
NEUROBIOLOGY OF DISEASE
2012; 45 (1): 253-263
Epilepsy is a common neurologic disorder yet no treatments aimed at preventing epilepsy have been developed. Several molecules including genes containing cAMP response elements (CREs) in their promoters have been identified that contribute to the development of epilepsy, a process called epileptogenesis. When phosphorylated cAMP response element binding protein (CREB) increases transcription from CRE regulated promoters. CREB phosphorylation is increased in rodent epilepsy models, and in the seizure onset region of humans with medically intractable epilepsy (Rakhade et al., 2005; Lee et al., 2007; Lund et al., 2008). Here we show that mice with decreased CREB levels (CREB(??) mutants) have a ~50% reduction in spontaneous seizures following pilocarpine induced status epilepticus (SE) and require more stimulation to electrically kindle. Following SE, brain derived neurotrophic factor (BDNF) and inducible cAMP early repressor (ICER) mRNAs are differentially up-regulated in the hippocampus and cortex of the CREB(??) mutants compared to wild-type mice, which may be contributing to differences in the severity of epilepsy. In contrast, we found no difference in KCC2 mRNA levels between the CREB(??) and wild-type mice after SE. The mechanism by which BDNF and ICER mRNAs increase specifically in the CREB(??) compared to wild-type mice following SE is not known. We did, however, find an increase in specific cAMP response element modulator (CREM) mRNA transcripts in the CREB(??) mutants that might be responsible for the differential regulation of BDNF and ICER after SE. Altering CREB activity following a neurologic insult provides a therapeutic strategy for modifying epileptogenesis.
View details for DOI 10.1016/j.nbd.2011.08.009
View details for Web of Science ID 000297883500028
View details for PubMedID 21867753
Neurotrophin-3 mRNA a putative target of miR21 following status epilepticus
2011; 1424: 53-59
Status epilepticus induces a cascade of protein expression changes contributing to the subsequent development of epilepsy. By identifying the cascade of molecular changes that contribute to the development of epilepsy we hope to be able to design therapeutics for preventing epilepsy. MicroRNAs influence gene expression by altering mRNA stability and/or translation and have been implicated in the pathology of multiple diseases. MiR21 and its co-transcript miR21, microRNAs produced from either the 5' or 3' ends of the same precursor RNA strand, are increased in the hippocampus following status epilepticus. We have identified a miR21 binding site, in the 3' UTR of neurotrophin-3 that inhibits translation. Neurotrophin-3 mRNA levels decrease in the hippocampus following SE concurrent with the increase in miR21. MiR21 levels in cultured hippocampal neurons inversely correlate with neurotrophin-3 mRNA levels. Treatment of hippocampal neuronal cultures with excess K(+)Cl(-), a depolarizing agent mimicking the episode of status epilepticus, also results in an increase in miR21 and a decrease in neurotrophin-3 mRNA. MiR21 is a candidate for regulating neurotrophin-3 signaling in the hippocampus following status epilepticus.
View details for DOI 10.1016/j.brainres.2011.09.039
View details for Web of Science ID 000297487600006
View details for PubMedID 22019057
Ganglioglioma arising from dysplastic cortex
2011; 52 (9): E106-E108
We report the case of a child who presented at 3 months of age with complex partial seizures, a linear facial nevus, and magnetic resonance imaging (MRI) showing delayed myelination and thickened cortex in the left temporal, parietal, and occipital regions. A repeat 3Tesla MRI scan with and without contrast at 6 months again showed cortical dysplasia of the left hemisphere. No other abnormalities were seen. A third scan at 3 years 6 months showed a 2.5 cm, round, hyperintense lesion on both T(2) and T(1) sequences. The lesion and surrounding dysplastic cortex were resected. Palmini grade IIA dysplasia and a ganglioglioma were diagnosed. These findings suggest that cellular components of cortical dysplasias have oncogenic potential.
View details for DOI 10.1111/j.1528-1167.2011.03124.x
View details for Web of Science ID 000294973700002
View details for PubMedID 21668439
Subependymal Giant Cell Astrocytoma (SEGA) Treatment Update
CURRENT TREATMENT OPTIONS IN NEUROLOGY
2011; 13 (4): 380-385
OPINION STATEMENT: Rates of regrowth after resection of subependymal giant cell astrocytoma (SEGA) are low, making surgical resection a successful and permanent therapeutic strategy. In addition to surgical resection of SEGAs, other treatment options now include medications and Gamma Knife™ therapy. Advising patients on medical versus surgical management of SEGAs is currently not easy. SEGAs have been reported to regrow if mTOR inhibitor therapy is stopped, raising the possibility that long-term medication may be required to prevent tumor growth and hydrocephalus. The question of regrowth following medication withdrawal will need to be addressed in more patients to help establish the optimal duration of therapy. The risks of surgery include acute morbidity and the permanent need for ventriculoperitoneal shunting, which must be balanced against the adverse effects of mTOR inhibitors, including immunosuppression (infections, mouth sores), hypercholesterolemia, and the need for chronic drug monitoring. Some additional benefits of mTOR inhibition in patients with tuberous sclerosis complex, however, may include shrinkage of angiofibromas and angiomyolipomas as well as a possible decrease in seizure burden. Recent reports of successful nonsurgical treatment of SEGAs are promising, and it is hoped that further specifics on dosing, duration, and long-term outcome will help patients and physicians to make informed therapeutic choices.Present treatment recommendations for SEGAs include routine surveillance neuroimaging and close clinical follow-up, paying particular attention to signs and symptoms of acute hydrocephalus. If symptoms arise, or if serial neuroimaging demonstrates tumor growth, neurosurgical intervention is recommended. When gross total resection is impossible, rapamycin and everolimus should be considered, but may not offer a durable response.
View details for DOI 10.1007/s11940-011-0123-z
View details for Web of Science ID 000292402500005
View details for PubMedID 21465222
Group I mGluR-regulated translation of the neuronal glutamate transporter, excitatory amino acid carrier 1
JOURNAL OF NEUROCHEMISTRY
2011; 117 (5): 812-823
Recently, we demonstrated that mRNA for the neuronal glutamate transporter, excitatory amino acid carrier 1 (EAAC1), is found in dendrites of hippocampal neurons in culture and in dendrites of hippocampal pyramidal cells after pilocarpine-induced status epilepticus (SE). We also showed that SE increased the levels of EAAC1 mRNA ~15-fold in synaptoneurosomes. In this study, the effects of SE on the distribution EAAC1 protein in hippocampus were examined. In addition, the effects of Group 1 mGluR receptor activation on the levels of EAAC1 protein were examined in synaptoneurosomes prepared from sham control animals and from animals that experience pilocarpine-induced SE. We find that EAAC1 immunoreactivity increases in pyramidal cells of the hippocampus after 3 h of SE. In addition, the group I mGluR agonist, (S)-3,5-dihydroxyphenylglycine (DHPG), caused an increase in EAAC1 protein levels in hippocampal synaptoneurosomes; this effect of DHPG was much larger (~3- to 5-fold) after 3 h of SE. The DHPG-induced increases in EAAC1 protein were blocked by two different inhibitors of translation but not by inhibitors of transcription. mGluR1 or mGluR5 antagonists completely blocked the DHPG-induced increases in EAAC1 protein. DHPG also increased the levels of glutamate receptor 2/3 protein, but this effect was not altered by SE. The DHPG-induced increase in EAAC1 protein was blocked by an inhibitor of the mammalian target of rapamycin or an inhibitor of extracellular signal-regulated kinase. These studies provide the first evidence EAAC1 translation can be regulated, and they show that regulated translation of EAAC1 is up-regulated after SE.
View details for DOI 10.1111/j.1471-4159.2011.07233.x
View details for Web of Science ID 000290225000004
View details for PubMedID 21371038
mRNA for the EAAC1 subtype of glutamate transporter is present in neuronal dendrites in vitro and dramatically increases in vivo after a seizure
2011; 58 (3): 366-375
The neuronal Na(+)-dependent glutamate transporter, excitatory amino acid carrier 1 (EAAC1, also called EAAT3), has been implicated in the control of synaptic spillover of glutamate, synaptic plasticity, and the import of cysteine for neuronal synthesis of glutathione. EAAC1 protein is observed in both perisynaptic regions of the synapse and in neuronal cell bodies. Although amino acid residues in the carboxyl terminal tail have been implicated in the dendritic targeting of EAAC1 protein, it is not known if mRNA for EAAC1 may also be targeted to dendrites. Sorting of mRNA to specific cellular domains provides a mechanism by which signals can rapidly increase translation in a local environment; this form of regulated translation has been linked to diverse biological phenomena ranging from establishment of polarity during embryogenesis to synapse development and synaptic plasticity. In the present study, EAAC1 mRNA sequences were amplified from dendritic samples that were mechanically harvested from low-density hippocampal neuronal cultures. In parallel analyses, mRNA for histone deacetylase 2 (HDAC-2) and glial fibrillary acidic protein (GFAP) was not detected, suggesting that these samples are not contaminated with cell body or glial mRNAs. EAAC1 mRNA also co-localized with Map2a (a marker of dendrites) but not Tau1 (a marker of axons) in hippocampal neuronal cultures by in situ hybridization. In control rats, EAAC1 mRNA was observed in soma and proximal dendrites of hippocampal pyramidal neurons. Following pilocarpine- or kainate-induced seizures, EAAC1 mRNA was present in CA1 pyramidal cell dendrites up to 200?m from the soma. These studies provide the first evidence that EAAC1 mRNA localizes to dendrites and suggest that dendritic targeting of EAAC1 mRNA is increased by seizure activity and may be regulated by neuronal activity/depolarization.
View details for DOI 10.1016/j.neuint.2010.12.012
View details for Web of Science ID 000295749500013
View details for PubMedID 21185901
Discrete gamma oscillations identify the seizure onset zone in some pediatric epilepsy patients
IEEE. 2011: 3095-3098
Intracranial electroencephalography (IEEG) plays an important role in guiding epilepsy surgery in pediatric epilepsy patients. Recently, there has been increased interest in higher frequency components of clinical IEEG recordings and their potential relationship to epileptogenic brain tissue. We employ a previously validated, automated discrete gamma oscillation (GO) detection algorithm to determine the prevalence of discrete gamma events over prolonged, representative segments of IEEG recorded from ten patients. Approximately 8 h of IEEG, 16 randomly selected 30-min segments of continuous interictal IEEG per patient, were analyzed. The electrodes within the seizure onset zone were found to have significantly higher mean GO activity averaged across these 16 segments in five of the ten patients. There was observed variability between individual 30-min segments in these patients, indicating that longer recordings of interictal activity improved localization. Our data suggest this method of automated GO detection across long periods may be useful in planning epilepsy surgery in certain children with intractable epilepsy. Further research is required to help determine which patients would benefit from this technique.
View details for Web of Science ID 000298810002205
View details for PubMedID 22254994
Aggrecan expression, a component of the inhibitory interneuron perineuronal net, is altered following an early-life seizure
NEUROBIOLOGY OF DISEASE
2010; 39 (3): 439-448
The perineuronal net (PN), a component of the neural extracellular matrix (ECM), is a dynamic structure whose expression decreases following diminished physiological activity. Here, we analyzed the effects of increased neuronal activity on the development of aggrecan, a component of the PN, in the hippocampus. We show aggrecan expression to be prominent around parvalbumin (PV) interneurons in the postnatal hippocampus. Moreover, after seizure induction in early life there was a significant increase in aggrecan expression in a region specific manner during the course of development. We conclude that increased neuronal activity leads to accelerated expression of PNs in the hippocampus that attenuates in the adult hippocampus. This study shows the dynamic nature of the PN component of the ECM and the role neuronal activity has in molding the extracellular milieu of inhibitory interneurons.
View details for DOI 10.1016/j.nbd.2010.05.015
View details for Web of Science ID 000280544100022
View details for PubMedID 20493259
Interictal EEG spikes identify the region of electrographic seizure onset in some, but not all, pediatric epilepsy patients
2010; 51 (4): 592-601
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.We employ a previously validated, computerized spike detector to measure and localize IED activity over prolonged, representative segments of IEEG recorded from 19 children with intractable, mostly extratemporal lobe epilepsy. Approximately 8 h of IEEG, randomly selected 30-min segments of continuous interictal IEEG per patient, were analyzed over all intracranial electrode contacts.When spike frequency was averaged over the 16-time segments, electrodes with the highest mean spike frequency were found to be within the seizure-onset region in 11 of 19 patients. There was significant variability between individual 30-min segments in these patients, indicating that large statistical samples of interictal activity were required for improved localization. Low-voltage fast EEG at seizure onset was the only clinical factor predicting IED localization to the seizure-onset region.Our data suggest that automated IED detection over multiple representative samples of IEEG may be of utility in planning epilepsy surgery for children with intractable epilepsy. Further research is required to better determine which patients may benefit from this technique a priori.
View details for DOI 10.1111/j.1528-1167.2009.02306.x
View details for Web of Science ID 000276245600012
View details for PubMedID 19780794
Seizures increase cell proliferation in the dentate gyrus by shortening progenitor cell-cycle length
2009; 50 (12): 2638-2647
A prolonged seizure, status epileptics (SE), is a potent stimulus for increased neurogenesis in the dentate gyrus of the hippocampus. Molecular mechanisms that regulate normal and pathologic cell birth in the dentate gyrus are poorly understood.Lithium-pilocarpine was used to induce SE in immature postnatal day 20 rats. Newborn cells in the dentate were labeled with bromo-deoxyuridine to determine a time-course of cell proliferation, and measure cell-cycle length. In addition, we studied expression by Western blot and immunohistochemistry of two known inhibitors of G(1)-S cell-cycle progression P27/Kip1 and P15/Ink4b following SE.Cell proliferation in the dentate gyrus increases starting 2 h after SE and is sustained for 40 days. Increased cell proliferation following SE is associated with a shortened dentate gyrus progenitor's cell cycle, 15 h in control to 12 h in the SE animals. To identify molecules responsible for the shortened progenitor cell cycle we studied inhibitors of cell-cycle progression P27/Kip1, and P15/Ink4b. We find decreased phosphorylation at P27/Kip1 Serine 10 and Threonine 187 following SE. Although total P27/Kip1 and P15/Ink4b levels were not altered after SE, P27/Kip1 immunoreactivity was minimal in newborn but increased with maturation of the dentate granule neurons.The sustained increase in dentate gyrus cell proliferation following SE provides a large pool of immature dentate granule cells prior to development of spontaneous seizures. A decrease in cell-cycle length of dentate gyrus progenitors is at least partially responsible for increased numbers of newborn cells following SE.
View details for DOI 10.1111/j.1528-1167.2009.02244.x
View details for Web of Science ID 000272128700016
View details for PubMedID 19674059
Topiramate and Adrenocorticotropic Hormone (ACTH) as Initial Treatment for Infantile Spasms
JOURNAL OF CHILD NEUROLOGY
2009; 24 (4): 400-405
Historically, adrenocorticotropic hormone was used as a first-line treatment for infantile spasms; however, there has been increasing use of topiramate as initial therapy. Here, we report a retrospective study of adrenocorticotropic hormone (ACTH) and topiramate as initial treatment for infantile spasms. The neurology patient database at the Children's Hospital of Philadelphia was searched using the International Classification of Diseases, Ninth Revision code for infantile spasms, and 50 patients were randomly chosen for chart review. We identified 31 patients receiving either adrenocorticotropic hormone or topiramate monotherapy (adrenocorticotropic hormone n = 12, topiramate n = 19) as a first-line treatment for infantile spasms. A total of 26 patients were symptomatic and 5 cryptogenic. Six patients treated with adrenocorticotropic hormone had resolution of clinical spasms and hypsarrhythmia within a month, but 3 relapsed. Of the 19 patients treated with topiramate, 4 patients eventually, though over a period of 0, 1, 8, or 69 months, had resolution of spasms and hypsarrhythmia.
View details for DOI 10.1177/0883073808324538
View details for Web of Science ID 000264593300001
View details for PubMedID 19225138
The role of transcription factors cyclic-AMP responsive element modulator (CREM) and inducible cyclic-amp early repressor (ICER) in epileptogenesis
2008; 152 (3): 829-836
Alterations in the brain that contribute to the development of epilepsy, also called epileptogenesis, are not well understood, which makes it difficult to develop strategies for preventing epilepsy. Here we have studied the role of the CRE binding transcription factors, cyclic-AMP responsive element modulator (CREM) and inducible cyclic-AMP early repressor (ICER), in the development of epilepsy following pilocarpine induced status epilepticus (SE) in mice. Following SE, ICER mRNA and protein are increased in neurons. The increase in ICER, however, is not necessary for neuronal injury following SE as pilocarpine treatment induces equivalent neuronal injury in pyramidal neurons of wild type and CREM/ICER null mice. Following SE, the CREM/ICER null mice develop a more severe epileptic phenotype experiencing approximately threefold more frequent spontaneous seizures. Together these data suggest that the increase in ICER mRNA following SE may have a role in suppressing the severity of epilepsy.
View details for DOI 10.1016/j.neuroscience.2007.10.064
View details for Web of Science ID 000254819900024
View details for PubMedID 18295410
Neurogenesis and epilepsy in the developing brain
2008; 49: 50-54
Multiple studies have highlighted how seizures induce different molecular, cellular, and physiologic consequences in an immature brain as compared to a mature brain. In keeping with these studies, seizures early in life alter dentate granule cell birth in different, and even opposing, fashion to adult seizure models (see Table 1). During the first week of rodent postnatal life, seizures decrease cell birth in the postictal period, but do not alter the maturation of newborn cells. Seizures during the second week of life have varied effects on dentate granule cell birth, either causing no change or increasing birth, and may promote a mild increase in neuronal survival. During the third and fourth weeks of life, seizures begin to increase cell birth similar to that seen in adult seizure models. Interestingly, animals that experienced seizure during the first month of life have an increase in cell birth during adulthood, opposite to the reported decrease in chronic animals experiencing a prolonged seizure as an adult. Children have more ongoing cell birth in the dentate gyrus than adults, and markers of cell division are further increased in children with refractory temporal lobe epilepsy. There are clear age-dependent differences in how seizures alter cell birth in the dentate gyrus both acutely and chronically. Future studies need to focus on how these changes in neurogenesis influence dentate gyrus function and what they imply for epileptogenesis and learning and memory impairments, so commonly found in children with temporal lobe epilepsy.
View details for DOI 10.1111/j.1528-1167.2008.01637.x
View details for Web of Science ID 000256395900007
View details for PubMedID 18522600
Comparison of novel computer detectors and human performance for spike detection in intracranial EEG
2007; 118 (8): 1744-1752
Interictal spikes in intracranial EEG (iEEG) may correlate with epileptogenic cortex, but review of interictal iEEG is labor intensive. Accurate automated spike detectors are necessary for understanding the role of spikes in epileptogenesis.The sensitivity, accuracy and reproducibility of three automated iEEG spike detectors were compared against two human EEG readers using iEEG segments from eight patients. A consensus set of detections was generated for detector calibration. Spike verification was calculated after both human EEG readers independently reviewed all detections.Humans and two of the three automated detectors demonstrated comparable accuracy. In four patients, automated spike detection sensitivity was >70% and accuracy was >50%. In the remaining four patients, EEG background morphology resulted in poorer performance. Blinded human verification accuracy was 76.7+/-6.6% for computer-detected spikes, and 84.5+/-4.1% for human-detected spikes.Automated iEEG spike detectors perform comparably to humans, but sensitivity and accuracy are patient dependent. Humans verified the majority of computer-detected spikes.In some patients automated detectors may be used for mapping spike occurrences in epileptic networks. This may reveal associations between spike distribution, seizure onset, and pathology.
View details for DOI 10.1016/j.clinph.2007.04.017
View details for Web of Science ID 000248668600012
View details for PubMedID 17544322
Seizures and antiepileptic drugs: Does exposure alter normal brain development ?
2006; 47 (12): 1999-2010
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.
View details for DOI 10.1111/j.1528-1167.2006.00894.x
View details for Web of Science ID 000242784000002
View details for PubMedID 17201696
Increased GABA(A)-receptor alpha 1-subunit expression in hippocampal dentate gyrus after early-life status epilepticus
2006; 47 (10): 1665-1673
Previous studies in neonatal (postnatal day 10) and adult rats suggest that status epilepticus (SE) induces changes in the alpha1 subunit of the GABA(A) 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.SE was induced with lithium-pilocarpine or kainate at P20. Animals were video-EEG monitored after SE to determine the presence or absence of spontaneous seizures. GABRA1 mRNA and protein levels were determined 7 days or 3 months later in SE-exposed and control animals by using a combination of aRNA amplification, Western blotting, and immunohistochemistry techniques.GABRA1 mRNA levels in DGNs of SE-exposed rats that did not become epileptic were higher than those in control rats, but were not different from DGNs in epileptic SE-exposed rats. GABRA1 protein levels in dentate gyrus were significantly increased in both epileptic and nonepileptic SE-exposed rats compared with controls. GABRA1 mRNA changes were region specific and did not occur in CA1 or CA3 areas of hippocampus. GABRA1 alterations were present by 1 week after P20 SE and were similar whether pilocarpine or kainate was used to induced SE.P20 SE results in persistent increases in GABRA1 levels selectively in dentate gyrus. These changes preceded the onset of epilepsy, were not model specific, and occurred in both epileptic and nonepileptic animals.
View details for DOI 10.1111/j.1528-1167.2006.00640.x
View details for Web of Science ID 000241191100011
View details for PubMedID 17054689
Dystrophic neuritic processes in epileptic cortex
2006; 70 (1): 49-58
Cortical dysplasia is a frequent finding in cortical resections from children with refractory epilepsy. Diagnostic criteria and a classification scheme for cortical dysplasia has been proposed, though the relationship between specific cortical dysplasia features and their causal relationship with epilepsy is poorly understood. We reviewed 28 surgical resections from children and identified a common and easily recognized feature of cortical dysplasia: maloriented, misshapen and occasionally coarse neurofilament stained process forming a dystrophic neuritic background. The dystrophic neuritic background was associated with other features of cortical dysplasia in all 28 patients with cortical dysplasia, 26 with refractory epilepsy and 2 patients with other neurologic diagnoses. In seven children with refractory epilepsy due to other pathologic diagnosis such as vascular or glial lesions, the dystrophic neuritic background was only found in one patient with a ganglioglioma and other features suggestive of an associated cortical dysplasia. Our data indicate that a dystrophic neuritic background is a common and relatively specific neuropathologic finding in cortical dysplasia.
View details for DOI 10.1016/j.eplepsyres.2006.03.006
View details for Web of Science ID 000239400600005
View details for PubMedID 16631351
Status epilepticus differentially alters AMPA and kainate receptor subunit expression in mature and immature dentate granule neurons
EUROPEAN JOURNAL OF NEUROSCIENCE
2006; 23 (11): 2857-2863
There is an increase in the birth of dentate granule neurons after status epilepticus (SE) and there are concurrent alterations in neurotransmitter receptor expression that may contribute to the development of spontaneous seizures. To determine whether newborn and/or mature dentate granule neurons have altered neurotransmitter receptor expression after SE, we dissected individual immature, PSA-NCAM-expressing, or mature, NeuN-expressing, dentate granule neurons 2 weeks after lithium-pilocarpine-induced SE in postnatal day 20 rats. Amplified single-cell RNA was used to probe reverse Northern blots containing alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and kainate neurotransmitter receptor subunits. Two weeks after lithium-pilocarpine-induced SE there were increases in AMPA GluR2 and kainate KA2 subunit mRNA and decreases in AMPA GluR3 and kainate GluR6 receptor subunit mRNA levels in mature dentate granule neurons. In contrast, only the kainate GluR6 subunit expression was reduced in immature dentate granule neurons after SE. Alterations in transcription of excitatory amino acid receptor subunits after SE occur primarily in the mature population of dentate granule neurons. Our findings suggest that neurotransmitter receptor gene expression is altered differently in immature and mature dentate granule neurons following SE, and may result in differential contributions of these two groups of dentate granule neurons to the subsequent development of epilepsy.
View details for DOI 10.1111/j.1460-9568.2006.04839.x
View details for Web of Science ID 000238185300003
View details for PubMedID 16819974
Heterogeneous GABA(A) receptor subunit expression in pediatric epilepsy patients
NEUROBIOLOGY OF DISEASE
2005; 18 (3): 484-491
The gamma-amino-butyric acid type A receptors (GABAAR) are a heteropentameric receptor complex, composed of 16 possible subunits in various combinations, forming a ligand-gated ion channel. Subunit composition is the primary determinant of GABAAR physiology and pharmacology. Here we have measured mRNA levels for 16 GABAAR subunits in isolated dentate granule neurons (DGN) from eight pediatric patients undergoing resective surgery for intractable epilepsy. We found tightly correlated expression of a subset of GABAAR subunit mRNAs within a single DGN (alpha1, gamma1, and gamma2; alpha4, alpha5, and beta2; alpha4 and beta3). Analysis of inter-patient variability (ANOVA) of eleven highly expressed GABAAR subunit mRNAs found seven of the subunits varied between patients, as did whole cell GABAAR currents. Due to inter-patient differences, there is heterogeneity in DGN GABAAR subunit mRNA and physiology within pediatric epilepsy patients. Patient-specific GABAAR expression might contribute to variability in anti-epileptic drug efficacy, side-effect profiles, and seizure susceptibility.
View details for Web of Science ID 000227820500008
View details for PubMedID 15755675
Fate of newborn dentate granule cells after early life status epilepticus
2004; 45 (1): 13-19
To determine the fate of newborn dentate granule cells (DGCs) after lithium-pilocarpine-induced status epilepticus (SE) in an immature rat.Postnatal day 20 (P20) rats were injected with lithium and pilocarpine to induce SE, and then with bromodeoxyuridine (BrdU) 4, 6, and 8 days later (P24, 26, and 28), and killed 1 day (P29), 1 week (P34), and 3 weeks (P50) after the last dose of BrdU for cell counts. Immunohistochemistry and TUNEL staining were performed to assess the fate of newborn DGCs.Pilocarpine-treated animals had significantly more BrdU-labeled DGCs than did littermate controls at all times. The day after the final BrdU injection (P29), sixfold more cells were found in pilocarpine-treated animals than in controls, which was reduced to threefold, 3 weeks later. A decrease in the BrdU-labeled cell density was noted from P29 to P50 in the control and pilocarpine-treated animals. Evidence of DGC cell death was seen in pilocarpine and control animals, with threefold more TUNEL-positive cells in the pilocarpine-treated than in the control animals at P29. The surviving newborn DGCs became mature neurons; expressing the neuronal marker NeuN in both control and pilocarpine-treated animals.These findings suggest that SE during postnatal development increases the birth and death of DGCs. A subset of the newborn DGCs survive and mature into dentate granule neurons, resulting in an increased population of immature DGCs after SE that may affect hippocampal physiology.
View details for Web of Science ID 000187964000003
View details for PubMedID 14692902
Dysplasia - A common finding in intractable pediatric temporal lobe epilepsy
2003; 61 (3): 365-368
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.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.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.CD was seen in 21 of 33 surgical specimens from children with refractory TLE, including those with and without other epilepsy risk factors.
View details for Web of Science ID 000184712600017
View details for PubMedID 12913199
Disorders of cortical development and epilepsy
ARCHIVES OF NEUROLOGY
2002; 59 (3): 361-365
There has been an impressive increase in our ability to identify and categorize patients with cortical development lesions over the past decade. The clinical features associated with disorders of cortical development (DCD) have been described, and epilepsy has been shown to be a frequent symptom. In this review, we categorize DCD based on their structure and discuss their underlying causes and clinical features. Just as the cause of each type of disorder is thought to be unique, each disorder also has distinct types of seizures, treatment strategies, and electroencephalographic features. Studies in human tissue and animal models of DCD have begun to shed light on why DCD are associated with epilepsy. Aberrant synaptic connections within the dysplastic tissue and between the dysplastic tissue and more normal-appearing adjacent tissue form an abnormal, hyperexcitable network that increases seizure susceptibility. In the future, strategies for blocking formation of the aberrant networks may prevent the development of epilepsy.
View details for Web of Science ID 000174386700002
View details for PubMedID 11890838
- Myelin and disorders that affect the formation and maintenance of this sheath MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES RESEARCH REVIEWS 2000; 6 (1): 47-58
Distinct structures and functions of related pre- and postsynaptic carbohydrates at the mammalian neuromuscular junction
MOLECULAR AND CELLULAR NEUROSCIENCE
1999; 13 (2): 105-118
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.
View details for Web of Science ID 000079942200003
View details for PubMedID 10192769
DISTINCT ADHESIVE PROPERTIES OF CILIARY AND CHOROID NEURONS FROM THE AVIAN CILIARY GANGLION
JOURNAL OF NEUROBIOLOGY
1995; 28 (3): 381-390
The avian ciliary ganglion (CG) contains two populations of neurons: ciliary neurons, which innervate striated muscle, and choroid neurons, which innervate vascular smooth muscle. We used cell size (ciliary cells are larger) and somatostatin immunoreactivity (which is restricted to choroid cells) as markers to compare the adhesive properties of these two neuronal types. Similar numbers of freshly dissociated embryonic chick ciliary and choroid neurons adhered to laminin (laminin 1) and polylysine, consistent with the fact that each population comprises about half of the ganglionic neurons. In contrast, severalfold more ciliary neurons than choroid neurons adhered to a recombinant fragment of a synapsespecific basal lamina protein, s-laminin/laminin beta 2. Moreover, severalfold more ciliary neurons than choroid neurons adhered to a plastic surface when assayed by the method of Needels et al. in serum-free medium. Adhesion to s-laminin and plastic appears to be mediated by different cell surface components, as adhesion to recombinant s-laminin is inhibited by the tripeptide, LRE, and by Ca2+ ions, but not by heparin, whereas adhesion to plastic is LRE and Ca2+ insensitive but heparin sensitive. Both adhesive differences are apparent at embryonic day 8, soon after the ciliary and choroid neurons have begun to form synapses. Thus, two sets of neurons in the CG that send axons through different nerves and innervate different targets also show distinct adhesive behaviors.
View details for Web of Science ID A1995TA42900009
View details for PubMedID 8568518
A MOTONEURON-SELECTIVE STOP SIGNAL IN THE SYNAPTIC PROTEIN S-LAMININ
1995; 14 (3): 549-559
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.
View details for Web of Science ID A1995QP23000008
View details for PubMedID 7695901
GATED MIGRATION - NEURONS MIGRATE ON BUT NOT ONTO SUBSTRATES CONTAINING S-LAMININ
1995; 167 (2): 609-616
Components of the extracellular matrix influence migration of diverse cell types. Some, such as laminin, promote neuronal migration, whereas others are nonpermissive or inhibitory. Here, we demonstrate that a recombinant fragment of s-laminin, a homologue of the laminin B1 chain, is a barrier to neuronal migration. NSC-34 (motoneuron-like) and ciliary ganglion cells were plated on substrates coated with alternating stripes of laminin and a mixture of laminin plus s-laminin. On these patterned substrates, cells seldom crossed from s-laminin-free to s-laminin-containing regions. Mutation of the tripeptide LRE, an adhesive site in s-laminin, abolished s-laminin's ability to block border crossing. However, overall rates of migration were similar on the two substrates. This behavior contrasts with that of previously reported barrier molecules, which decreases rates of cell migration when mixed with permissive substrates. Instead, s-laminin appears to block cell migration through a "gating" mechanism that acts primarily at borders.
View details for Web of Science ID A1995QK99000017
View details for PubMedID 7875382
S-LAMININ - MAPPING TO MOUSE CHROMOSOME-9 AND EXPRESSION IN THE LINKED MUTANTS TIPPY AND DUCKY
1993; 16 (1): 278-281
S-Laminin, a homologue of the laminin B1 chain, is present in a subset of basal laminae, including those of the skeletal neuromuscular junction and the renal glomerulus. Here, we show that the distribution and apparent size of murine S-laminin are similar to those documented previously for rat and human. We then use interspecific backcross analysis to map the S-laminin (Lams) gene to mouse chromosome 9. Thus, it is unlinked to genes for the laminin A, B1, and B2 chains. Finally, because the Lams gene mapped near two mutations that affect neuromuscular function, ducky (du) and tippy (tip), we assayed S-laminin by Southern blotting, immunoblotting, and immunohistochemistry in these mutants. No abnormality of the S-laminin gene or protein was detectable in either mutant.
View details for Web of Science ID A1993KW20500046
View details for PubMedID 8486374
PRIMARY SEQUENCE OF A MOTOR NEURON SELECTIVE ADHESIVE SITE IN THE SYNAPTIC BASAL LAMINA PROTEIN S-LAMININ
1989; 59 (5): 905-913
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.
View details for Web of Science ID A1989CC79800015
View details for PubMedID 2590946
RESTORATION OF CELL-VOLUME AND THE REVERSAL OF CARBOHYDRATE TRANSPORT AND GROWTH-INHIBITION OF OSMOTICALLY UP-SHOCKED ESCHERICHIA-COLI
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
1985; 126 (1): 442-449
Resumption of growth in osmotically upshocked Escherichia coli was effected only by an external stimulus (betaine treatment) in severe upshock, but was spontaneous in less severe upshock. In either case, growth resumption was preceded by a reversal of glucose transport inhibition, and that reversal was preceded by a recovery of cell volume. We hypothesize that deformation of the membrane by osmotic stress results in conversion of a membrane component of the transport system to a less functional conformation, which results in the inhibition of transport and the consequent inhibition of growth. Relief of the deformation would then allow recovery to a more functional conformation, reversal of transport inhibition, and then resumption of growth.
View details for Web of Science ID A1985ABH5300063
View details for PubMedID 3882088