Functional aspects of early brain development are preserved in tuberous sclerosis complex (TSC) epileptogenic lesions

Gabriele Ruffolo, Anand M. Iyer, Pierangelo Cifelli, Cristina Roseti, Angelika Mühlebner, Jackelien van Scheppingen, Theresa Scholl, Johannes A. Hainfellner, Martha Feucht, Pavel Krsek, Josef Zamecnik, Floor Jansen, W. G M Spliet, Cristina Limatola, Eleonora Aronica, Eleonora Palma

Research output: Contribution to journalArticle

Abstract

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 15 years 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.

Original languageEnglish
Pages (from-to)93-101
Number of pages9
JournalNeurobiology of Disease
Volume95
DOIs
Publication statusPublished - Nov 1 2016

Keywords

  • Brain development
  • Epilepsy
  • GABA receptor
  • Oocytes
  • Tuberous sclerosis complex

ASJC Scopus subject areas

  • Neurology

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  • Cite this

    Ruffolo, G., Iyer, A. M., Cifelli, P., Roseti, C., Mühlebner, A., van Scheppingen, J., Scholl, T., Hainfellner, J. A., Feucht, M., Krsek, P., Zamecnik, J., Jansen, F., Spliet, W. G. M., Limatola, C., Aronica, E., & Palma, E. (2016). Functional aspects of early brain development are preserved in tuberous sclerosis complex (TSC) epileptogenic lesions. Neurobiology of Disease, 95, 93-101. https://doi.org/10.1016/j.nbd.2016.07.014