title: Loss of cortical GABA terminals in Unverricht-Lundborg disease.
abstract: Unverricht-Lundborg disease (ULD) is the most common progressive myoclonic epilepsy. Its etiology has been identified in a defect of a protease inhibitor, cystatin B (CSTB), but the mechanism(s) by which this defect translates in the clinical manifestations of the disease are still obscure. We tested the hypothesis that ULD is accompanied by a loss of cortical GABA inhibition in a murine model (the CSTB knockout mouse) and in a human case. Cortical GABA signaling has been investigated measuring VGAT immunohistochemistry (a histological marker of the density of GABA terminals), GABA release from synaptosomes and paired-pulse stimulation. In CSTB knockout mice, a progressive decrease in neocortex thickness was found, associated with a prevalent loss of GABA interneurons. A marked reduction in VGAT labeling was found in the cortex of both CSTB knockout mice and an ULD patient. This implicates a reduction in GABA synaptic transmission, which was confirmed in the mouse model as reduction in GABA release from isolated nerve terminals and as loss of electrophysiologically measured GABA inhibition. The alterations in VGAT immunolabeling progressed in time, paralleling the worsening of myoclonus. These results provide direct evidence that loss of cortical GABA input occurs in a relevant animal model and in a case of human ULD, leading to a condition of latent hyperexcitability that favors myoclonus and seizures. These findings contribute to the understanding of the pathogenic mechanism of ULD and of the neurobiological basis of the effect of currently employed drugs.
authors.affiliation: Department of Clinical and Experimental Medicine, University of Ferrara, Ferrara, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Buzzi
authors.forename: Maia
authors.initials: M
authors.lastname: Chikhladze
authors.forename: Chiara
authors.initials: C
authors.lastname: Falcicchia
authors.forename: Beatrice
authors.initials: B
authors.lastname: Paradiso
authors.forename: Giovanni
authors.initials: G
authors.lastname: Lanza
authors.forename: Marie
authors.initials: M
authors.lastname: Soukupova
authors.forename: Matteo
authors.initials: M
authors.lastname: Marti
authors.forename: Michele
authors.initials: M
authors.lastname: Morari
authors.forename: Silvana
authors.initials: S
authors.lastname: Franceschetti
authors.forename: Michele
authors.initials: M
authors.lastname: Simonato
mesh_terms: D000328:Adult; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D018345:Mice, Knockout; D008875:Middle Aged; D017729:Presynaptic Terminals / Q000378:metabolism / Q000473:pathology*; D020194:Unverricht-Lundborg Syndrome / Q000378:metabolism / Q000473:pathology*; D005680:gamma-Aminobutyric Acid / Q000172:deficiency*
chemical_list: D005680:gamma-Aminobutyric Acid