Amina Gargouri-Berrechid

Using KASP technique to screen LRRK2 G2019S mutation in a large Tunisian cohort

BackgroundIn North African populations, G2019S mutation in LRRK2 gene, encoding for the leucine-rich repeat kinase 2, is the most prevalent mutation linked to familial and sporadic Parkinson’s disease (PD). Early detection of G2019S by fast genetic testing is very important to guide PD’s diagnosis and support patients and their family caregivers for better management of their life according to disease’s evolution.MethodsIn our study, a genetic PD’s diagnosis tool was developed for large scale genotyping using Kompetitive Allele Specific PCR (KASP) technology. We investigated G2019S’s frequency in 250 Tunisian PD patients and 218 controls.ResultsWe found that 33.6% of patients and 1.3% of controls were carriers. Demographic characteristics of patients with G2019S had no differences compared with non-carrier patients. Thereby, we could emphasize the implication of G2019S in PD without any distinctive demographic factors in the studied cohort. Sixty patients out of 250 were genotyped using Taqman assay and Sanger sequencing. The genotyping results were found to be concordant with KASP assay.ConclusionsThe G2019S mutation frequency in our cohort was similar to that reported in previous studies. Comparing to Taqman assay and Sanger sequencing, KASP was shown to be a reliable, time and cost effective genotyping assay for routine G2019S screening in genetic testing laboratories.

Clinical and genetic study of Tunisian families with genetic generalized epilepsy: contribution of CACNA1H and MAST4 genes

Genetic generalized epilepsies (GGE) (childhood absence epilepsy (CAE), juvenile myoclonic epilepsy (JME) and epilepsy with generalized tonic-clonic seizures (GTCS)) are mainly determined by genetic factors. Since few mutations were identified in rare families with autosomal dominant GGE, a polygenic inheritance was suspected in most patients. Recent studies on large American or European cohorts of sporadic cases showed that susceptibility genes were numerous although their variants were rare, making their identification difficult. Here, we reported clinical and genetic characteristics of 30 Tunisian GGE families, including 71 GGE patients. The phenotype was close to that in sporadic cases. Nineteen pedigrees had a homogeneous type of GGE (JME-CAE-CGTS), and 11 combined these epileptic syndromes. Rare non-synonymous variants were selected in probands using a targeted panel of 30 candidate genes and their segregation was determined in families. Molecular studies incriminated different genes, mainly CACNA1H and MAST4. The segregation of at least two variants in different genes in some pedigrees was compatible with the hypothesis of an oligogenic inheritance, which was in accordance with the relatively low frequency of consanguineous probands. Since at least 2 susceptibility genes were likely shared by different populations, genetic factors involved in the majority of Tunisian GGE families remain to be discovered. Their identification should be easier in families with a homogeneous type of GGE, in which an intra-familial genetic homogeneity could be suspected.

Genetic Analysis of TREM2 Variants in Tunisian Patients with Alzheimer's Disease

Objective: Rare variants in the TREM2 gene have been reported to significantly increase the risk of Alzheimer’s disease in Caucasian populations. Hitherto, this association was not studied in North African populations. In this work, we aimed to study the association between TREM2 exon 2 variants and the risk of late-onset Alzheimer’s disease (LOAD) in a Tunisian population. Subjects and Methods: We sequenced exon 2 of TREM2 in a Tunisian cohort of 172 LOAD patients and 158 control subjects. We used the Fisher exact test to compare the distribution of allelic frequencies between the two groups. Results: We identified 4 previously reported nonsynonymous variants (p.Asp39Glu, p.Arg62His, p.Thr96Lys, and p.Val126Gly) and 1 novel synonymous variant (p.Gln109Gln), none of which was significantly associated with the risk of Alzheimer’s disease. Moreover, the rare TREM2 variant (p.Arg47His), which was considered to be a risk factor for Alzheimer’s disease in European descent populations, was not detected in our cohort. Conclusion: These findings do not support a major role for TREM2 in the pathogenesis of LOAD in the Tunisian population.

P - 2 Intérêt de l’étude des mouvements oculaires dans les troubles hyperactifs avec déficit de l’attention

Introduction Le trouble de l’attention avec hyperactivite (THADA) est un trouble frequent en psychiatrie sans marqueur pour la maladie. L’etude des mouvements oculaires pourrait y etre utile en tant que critere diagnostic objectif. Objectifs Etudier l’interet des etudes des mouvements oculaires (MOC) dans le trouble de l’attention avec hyperactivite. Methodes Nous avons mene une etude comparative des mouvements oculaires chez 7 enfants ayant une hyperactivite avec deficit de l’attention confirmee versus 7 enfants sains apparaies avec l’âge et le sexe. 2 paradigmes ont ete etudies les pro-saccades avec un « Overlap condition » et la poursuite. Le test T Student a ete utilise pour l’etude statistique. Resultats Les prosaccades etaient enregistrees dans 5 cas sur 7 chez les patients hyperactifs et dans tous les sujets temoins. Les latences des prosaccades etaient allongees comparativement aux sujets temoin. La moyenne etait de 299 ms + 91 par rapport a 227 ms + 15,8 ; la difference etait statistiquement significative avec un P Discussion La presence d’un allongement des latences des prosaccades a ete retrouvee chez les patients hyperkinetiques avec deficit de l’attention et serait secondaire a un dysfonctionnement prefrontal (Todd et al. 2001, Mostofsky et al. 2001 et Douglas et al. 2003). Conclusion L’etude des MOC est un examen utile chez les THADA. Cet examen montre une alteration significative des latences des prosaccades qui pourrait donc etre un parametre objectif pour le diagnostic positif avec les autres criteres.

B - 2 Somnambulisme familial

Introduction Le somnambulisme est une forme de parasomnie qui constitue un diagnostic differentiel avec l’epilepsie du fait de leurs similarites cliniques. Une predisposition genetique et des formes familiales sont decrites. Objectifs Le but de notre travail est d’insister sur l’importance d’identifier des parasomnies devant des manifestations paroxystiques au cours du sommeil, et de savoir les distinguer cliniquement des crises epileptiques. Methodes Une enquete familiale etait realisee aupres de cas index consultant pour somnambulisme. L’interrogatoire avait identifie des cas similaires et un arbre genealogique etait etabli pour chaque famille. Une etude electroencephalographie etait realisee chez tous les cas index. L’etude genetique est en cours. Resultats Il s’agissait de 4 familles de somnambulisme de transmission autosomique dominante. Au minimum 3 cas similaires existaient dans chaque famille. Le somnambulisme etait souvent associe a une somniloquie. L’âge de debut se situait aux alentours de 3 ans avec une nette diminution des acces vers l’âge de 20 ans. Une epilepsie faite de crises partielles et generalisees de survenue essentiellement nocturnes etait trouvee dans 3 familles. Discussion L’heredite intervient dans la survenue du somnambulisme. Dans 80 p. 100 des cas, les sujets atteints ont au moins un membre de la famille affecte, et les jumeaux monozygotes sont affectes de facon concordante 6 fois plus souvent que les dizygotes. La transmission est essentiellement autosomique dominante. Aucun locus n’a ete identifie pour ce trouble. Son association a une epilepsie est possible. Conclusion La distinction entre parasomnie et epilepsie est essentielle, leur association chez un meme individu est possible. Un mecanisme physiopathologique commun est suggere. Les formes familiales refletent une predisposition genetique.