Tuberous sclerosis complex (TSC) is a rare multi-system genetic disease characterized by several neurological disorders, the most common of which is the refractory epilepsy caused by highly epileptogenic cortical lesions. Previous studies suggest an alteration of GABAergic and glutamatergic transmission in TSC brain indicating an unbalance of excitation/inhibition that can explain, at least in part, the high incidence of epilepsy in these patients. Here we investigate whether TSC cortical tissues could retain GABAA and AMPA receptors at early stages of human brain development thus contributing to the generation and recurrence of seizures. Given the limited availability of pediatric human brain specimens, we used the microtransplantation method of injecting Xenopus oocytes with membranes from TSC cortical tubers and control brain tissues. Moreover, qPCR was performed to investigate the expression of GABAA and AMPA receptor subunits (GABAA α1-5, β3, γ2, δ; GluA1, GluA2) and cation chloride co-transporters NKCC1 and KCC2. The evaluation of nine human cortical brain samples, from 15 gestation weeks to 15years old, showed a progressive shift towards more hyperpolarized GABAA reversal potential (EGABA). This shift was associated with a differential expression of the chloride cotransporters NKCC1 and KCC2. Furthermore, the GluA1/GluA2 mRNA ratio of expression paralleled the development process. On the contrary, in oocytes micro-transplanted with epileptic TSC tuber tissue from seven patients, neither the GABAA reversal potential nor the GluA1/GluA2 expression showed similar developmental changes. Our data indicate for the first time, that in the same cohort of TSC patients, the pattern of both GABAAR and GluA1/GluA2 functions retains features that are typical of an immature brain. These observations support the potential contribution of altered receptor function to the epileptic disorder of TSC and may suggest novel therapeutic approaches. Furthermore, our findings strengthen the novel hypothesis that other developmental brain diseases can share the same hallmarks of immaturity leading to intractable seizures.

Department of Epilepsy Institute in the Netherlands Foundation Heemstede The Netherland

Department of Pathology Academic Medical Center University of Amsterdam The Netherlands

Department of Pathology Academic Medical Center University of Amsterdam The Netherlands; Department of Pediatrics Medical University Vienna Austria

Department of Pathology and Molecular Medicine Charles University 2nd Medical School Motol University Hospital Prague Czech Republic

Department of Pathology University Medical Center Utrecht The Netherlands

Department of Pediatric Neurology Brain Center Rudolf Magnus University Medical Center Utrecht The Netherlands

Department of Pediatric Neurology Charles University 2nd Medical School Motol University Hospital Prague Czech Republic

Department of Pediatrics Medical University Vienna Austria

Department of Physiology and Pharmacology Istituto Pasteur Fondazione Cenci Bolognetti University of Rome Sapienza Rome Italy

Department of Physiology and Pharmacology Istituto Pasteur Fondazione Cenci Bolognetti University of Rome Sapienza Rome Italy; IRCCS Neuromed Isernia Italy

Department of Physiology and Pharmacology Istituto Pasteur Fondazione Cenci Bolognetti University of Rome Sapienza Rome Italy; IRCCS San Raffaele Pisana Rome Italy

Department of Physiology and Pharmacology Istituto Pasteur Fondazione Cenci Bolognetti University of Rome Sapienza Rome Italy; Ri MED Foundation Palermo Italy

Institute of Neurology Medical University Vienna Austria

IRCCS San Raffaele Pisana Rome Italy

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Prediction of Neurodevelopment in Infants With Tuberous Sclerosis Complex Using Early EEG Characteristics