International Journal of Neuroscience, 2014; 124(2): 102–109 Copyright © 2014 Informa Healthcare USA, Inc. ISSN: 0020-7454 print / 1543-5245 online DOI: 10.3109/00207454.2013.828723 A Shared Haplotype Indicates a Founder Event in Unverricht–Lundborg Disease Patients from Serbia Miljana Kecmanovi´ c, 1 Aleksandar J. Risti´ c, 2 Marko Ercegovac, 2 Milica Keckarevi´ c-Markovi´ c, 1 Duˇ san Keckarevi´ c, 1 Dragoslav Soki´ c, 2 and Stanka Romac 1 1 Faculty of Biology, University of Belgrade, Belgrade, Serbia; 2 Clinic of Neurology, Clinical Centre of Serbia, Medical Faculty, Belgrade, Serbia Unverricht–Lundborg disease (ULD) is an autosomal recessive disorder caused by dodecamer repeat expansion in the promoter region of the cystatin B (CSTB) gene in approximately 90% of the disease alleles worldwide. This study presents results of genetic indings in four Serbian unrelated patients with clinical and molecular diagnosis of ULD. Using newly established PCR protocol with betaine, we detected a homozygous expansion of dodecamer repeats in the CSTB gene in four patients with clinical diagnosis of ULD. Our results are in agreement with previous studies showing that dodecamer repeats expansion is the most common mutation associated with ULD. Haplotype analysis of eight unrelated ULD chromosomes was performed using seven markers lanking CSTB gene and one intragenic variant. We demonstrated the existence of a founder effect, strongly supported by LD calculations. Size of the minimal common haplotype implies that the most recent common ancestor of the Serbian ULD patients lived about 110 generations ago. We showed that Serbian ULD patients share the same common ancestor with patients from Baltic countries and North Africa. In the light of our data, we proposed extended minimal common haplotype, which could be considered as initial haplotype of the founder event common for Serbian, Baltic, and North African ULD patients. KEYWORDS: epilepsy, cystatin B, expansion repeat, haplotype analysis, founder event Introduction Unverricht–Lundborg disease (ULD) (EPM1, OMIM 254800) is the most common form of progressive myoclonic epilepsies (PMEs) and is characterized by stimulus-sensitive myoclonus and tonic-clonic seizures beginning between ages 6 and 16 [1]. The disease has variable rate of progression within and between families [1]. ULD is the most prevalent around the Baltic Sea and in the western Mediterranean region [2–4], but many sporadic cases are reported worldwide [5–10]. ULD is an autosomal recessive disorder caused by mutations in the CSTB gene (OMIM# 601145) located on chromosome 21q22.3 [11]. Almost all patients with Received 1 December 2012; revised 22 July 2013; accepted 22 July 2013. Correspondence: Miljana Kecmanovi´ c, PhD, Faculty of Biology, University of Belgrade, Studentski trg 16, 11000 Belgrade, Serbia. Tel: +381-11-2639100. Fax: +381-11-2639100, E-mail: miljana@bio.bg.ac.rs the ULD have at least one allele with the dodecamer re- peat expansion in the promoter region of the CSTB gene [12–14]. Over 90% of ULD patients are homozygous for the expansion, while the remaining patients are com- pound heterozygotes, with expansion in one and with one of the rare mutation in other CSTB allele [14]. This minisatellite is normally polymorphic, with two or three copies, while the number of expanded repeats in patients is greater than 30 [15]. Haplotype analysis of chromosomes with the expan- sion in the CSTB from Northern African and Western European patients showed connection between the ex- pansion and two main haplotypes, A and C, implying that there were only a few founder mutations associated with ULD worldwide [4]. Here, we describe indings in 20 patients with my- oclonic epilepsy with heterogeneous course. We per- formed haplotype analysis using eight genetic markers in order to examine if the most common ULD muta- tion is founder mutation in Serbia or is it one of a few founder mutations worldwide [4], and estimated the pe- riod of its introducing to Serbia. 102 Int J Neurosci Downloaded from informahealthcare.com by Universitaet Zuerich on 05/29/14 For personal use only.