Anti-CSTB monoclonal antibody, clone N2-D2

Unverricht-Lundborg disease (ULD) is a progressive myoclonus epilepsy common in Finland and North Africa, and less common in Western Europe. ULD is mostly caused by expansion of a dodecamer repeat in the cystatin B gene (CSTB) promoter. We performed a haplotype study of ULD chromosomes (ULDc) with the repeat expansion. We included 48 West European Caucasian (WEC) and 47 North African (NA) ULDc. We analysed eight markers flanking CSTB (GT10-D21SI890-D2IS1885-D21S2040-D21S1259-CSTB-D21S1912-PFKL-D21S171) and one intragenic variant in the CSTB 3'UTR (A2575G). We observed a founder effect in most of the NA ULD patients, as 61.7% of the NA ULDc (29/47) shared the same haplotype, A1 (1-1-A-1-6-7), for markers D21S1885-D21S2040-A2575G-D21S1259-D21S1912-PFKL. Moreover, if we considered only the markers D21S1885, D21S2040, A2575G and D21S1259, 43 of the 47 NA ULDc shared the same alleles 1-1-A-1, haplotype A. As previously shown, the WEC ULDc were heterogeneous. However, the Baltic haplotype, A3 (5-1-1-A-1-1), was observed in ten WEC ULDc (20.8%) and the CSTB 3'UTR variant, which we called the Alps variant, was observed in 17 ULDc (35.4%). Finally, as almost all NA patients, like Scandinavian patients, were of the haplotype A, we assumed that there was an ancient common founder effect in NA and Baltic ULD patients. We estimated that the putative most recent common ancestral ULD carrier with this haplotype A must have existed about 2,500 years ago (100-150 generations). Finally, this work provides evidence for the existence of only a small number of founder mutations in ULD.

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. (C) 2012 Elsevier Inc. All rights reserved.