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Initiation of epileptiform activity in a rat model of periventricular nodular heterotopia.

ABSTRACT: Periventricular nodular heterotopia (PNH) is, in humans, often associated with difficult-to-control epilepsy. However, there is considerable controversy about the role of the PNH in seizure generation and spread. To study this issue, we have used a rat model in which injection of methylazoxymethanol (MAM) into pregnant rat dams produces offspring with nodular heterotopia-like brain abnormalities.Electrophysiologic methods were used to examine the activity of the MAM-induced PNH relative to activity in the neighboring hippocampus and overlying neocortex. Recordings were obtained simultaneously from these three structures in slice preparations from MAM-exposed rats and in intact animals. Bath application or systemic injection of bicuculline was used to induce epileptiform activity.In the in vitro slice, epileptiform discharge was generally initiated in hippocampus. In some cases, independent PNH discharge occurred, but the PNH never "led" discharges in hippocampus or neocortex. Intracellular recordings from PNH neurons confirmed that these cells received synaptic drive from both hippocampus and neocortex, and sent axonal projections to these structures-consistent with anatomic observations of biocytin-injected PNH cells. In intact animal preparations, bicuculline injection resulted in epileptiform discharge in all experiments, with a period of ictal-like electrographic activity typically initiated within 2-3 min after drug injection. In almost all animals, the onset of ictus was seen synchronously across PNH, hippocampal, and neocortical electrodes; in a few cases, the PNH electrode (histologically confirmed) did not participate, but in no case was activity initiated in the PNH electrode. Interictal discharge was also synchronized across all three electrodes; again, the PNH never "led" the other two electrodes, and typically followed (onset several milliseconds after hippocampal/neocortical discharge onset).These results do not support the hypothesis that the PNH lesion is the primary epileptogenic site, since it does not initiate or lead epileptiform activity that subsequently propagates to other brain regions.

SUBMITTER: Tschuluun N

PROVIDER: S-EPMC3230777 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Initiation of epileptiform activity in a rat model of periventricular nodular heterotopia.

Tschuluun Naranzogt N Jürgen Wenzel H H Doisy Emily T ET Schwartzkroin Philip A PA

Epilepsia 20110920 12

<h4>Purpose</h4>Periventricular nodular heterotopia (PNH) is, in humans, often associated with difficult-to-control epilepsy. However, there is considerable controversy about the role of the PNH in seizure generation and spread. To study this issue, we have used a rat model in which injection of methylazoxymethanol (MAM) into pregnant rat dams produces offspring with nodular heterotopia-like brain abnormalities.<h4>Methods</h4>Electrophysiologic methods were used to examine the activity of the M ...[more]

PMID: 21933177

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Project description:Heterozygous loss of function mutations within the Filamin A gene in Xq28 are the most frequent cause of bilateral neuronal periventricular nodular heterotopia (PVNH). Most affected females are reported to initially present with difficult to treat seizures at variable age of onset. Psychomotor development and cognition may be normal or mildly to moderately impaired. Distinct associated extracerebral findings have been observed and may help to establish the diagnosis including patent ductus arteriosus Botalli, progressive dystrophic cardiac valve disease and aortic dissection, chronic obstructive lung disease or chronic constipation. Genotype-phenotype correlations could not yet be established.Sanger sequencing and MLPA was performed for a large cohort of 47 patients with Filamin A associated PVNH (age range 1 to 65 years). For 34 patients more detailed clinical information was available from a structured questionnaire and medical charts on family history, development, epileptologic findings, neurological examination, cognition and associated clinical findings. Available detailed cerebral MR imaging was assessed for 20 patients.Thirty-nine different FLNA mutations were observed, they are mainly truncating (37/39) and distributed throughout the entire coding region. No obvious correlation between the number and extend of PVNH and the severity of the individual clinical manifestation was observed. 10 of the mutation carriers so far are without seizures at a median age of 19.7 years. 22 of 24 patients with available educational data were able to attend regular school and obtain professional education according to age.We report the clinical and mutation spectrum as well as MR imaging for a large cohort of 47 patients with Filamin A associated PVNH including two adult males. Our data are reassuring in regard to psychomotor and cognitive development, which is within normal range for the majority of patients. However, a concerning median diagnostic latency of 17 to 20 years was noted between seizure onset and the genetic diagnosis, intensely delaying appropriate medical surveillance for potentially life threatening cardiovascular complications as well as genetic risk assessment and counseling prior to family planning for this X-linked dominant inherited disorder with high perinatal lethality in hemizygous males.

Project description:BACKGROUND: X-linked periventricular nodular heterotopia is a disorder of neuronal migration resulting from mutations in the filamin A gene. This is an X-linked dominant condition where most affected patients are female and present with seizures. Extra-cerebral features such as cardiac abnormalities and thrombocytopenia have also been documented. Loss of function mutations in filamin A are predicted to result in prenatal lethality in males. Somatic mosaicism and mutations that lead to partial loss of function of the protein are hypothesized to explain viability of males reported in the literature. We report the first case of germline mosaicism involving a loss of function mutation in filamin A in a family where brain MRI, clinical exam, and mutation analysis is normal in both biological parents. CASE PRESENTATION: The index patient, a 39 year old female with normal development, had her first seizure at 24 years with no evidence of any precipitating factors. Brain MRI shows bilateral periventricular nodular heterotopia. She has thrombocytopenia and an echocardiogram at age 32 years revealed a mildly dilated aortic root and ascending aorta with mild aortic regurgitation. The second patient, the 36 year old younger sister of the index case, is currently healthy with no evidence of seizures or cardiac abnormalities. Her brain MRI is consistent with bilateral periventricular nodular heterotopia. The mother is healthy at 57 years of age with a normal brain MRI. The father is healthy at 59 years of age with a normal brain MRI. DNA sequencing of lymphocyte extracted DNA from the two sisters shows a c.2002C?>?T transition in exon 13 of filamin A resulting in a p.Gln668Ter mutation. This nonsense mutation was not detected in peripheral blood lymphocytes from the unaffected parents. CONCLUSION: This report provides evidence for germline mosaicism in filamin A-associated periventricular nodular heterotopia. This case must now be considered when providing genetic counseling to families where a proband presents as an isolated case and parental investigations are unremarkable.

Project description:RationalePeriventricular nodular heterotopia-7 (PVNH7) is a neurodevelopmental disorder associated with improper neuronal migration during neurogenesis in cortex development caused by pathogenic variants in the NEDD4L gene.Patient concernsWe report the case of a polystigmatized 2-year-old boy having significant symptomatologic overlap with PVNH7, such as delayed psychomotor and mental development, seizures and infantile spasms, periventricular nodular heterotopia, polymicrogyria, cleft palate, 2 to 3 toe syndactyly, hypotonia, microretrognathia, strabismus, and absent speech and walking. The patient showed also distinct symptoms falling outside PVNH7 symptomatology, also present in the proband's older brother, such as blue sclerae, hydronephrosis, transversal palmar crease (found also in their father), and bilateral talipes equinovarus. In addition, the patient suffered from many other symptoms.DiagnosesThe boy, his brother and their parents were subjected to whole-exome sequencing. Because of uncertainties in symptomatology and inheritance pattern, the top-down approach was hard to apply. Using the bottom-up approach, we identified a known pathogenic variant, NM_001144967.2(NEDD4L):c.2677G>A:p.Glu893Lys, in the proband's genome that absented in any other analyzed family member, suggesting its de novo origin.Interventions and outcomesThe patient was treated with Convulex 300 mg/mL for the successful seizure control and Euthyrox 25mg for the treatment of thyroid malfunction. He also took various supplements for the metabolism support and digestion regulation. Moreover, the patient underwent the corrective surgeries of cleft palate and talipes equinovarus.LessonsWe successfully identified the causative mutation NM_001144967.2(NEDD4L):c.2677G>A:p.Glu893Lys explaining symptoms overlapping those reported for PVNH7. Symptoms shared with the brother were not explained by this variant, since he was not a carrier of the pathogenic NEDD4L variant. These are most likely not extended phenotypes of PVNH7, rather an independent clinical entity caused by a yet unidentified genetic factor in the family, highlighting thus the importance of thorough evaluation of symptomatology and genomic findings in affected and unaffected family members, when such data are available.

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Initiation of epileptiform activity in a rat model of periventricular nodular heterotopia.

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Initiation of epileptiform activity in a rat model of periventricular nodular heterotopia.

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