Identification of a novel mutation (Leu282Arg) of the human presenilin 1 gene in Alzheimer’s disease Jesu ´s Aldudo a , Marı ´a J. Bullido a , Txomin Arbizu c , Rafael Oliva b , Fernando Valdivieso a, * a Departamento de Biologı´a Molecularand Centro de Biologı´a Molecular‘Severo Ochoa’, Universidad Auto ´ noma de Madrid, Cantoblanco, 28049 Madrid, Spain b Genetics Service, Hospital Clı ´ nic i Provincial and Institut August Pi i Sunyer, Villarroel 170, 08036 Barcelona, Spain c Neurology Service, Hospital de Vellvitge, Barcelona, Spain Received 13 October 1997; accepted 5 December 1997 Abstract Many different mutations, causative of Alzheimer’s disease, have been found in the presenilin-1 gene (PS-1). We have developed a screening method based on denaturing gradient gel electrophoresis (DGGE), which allows the mutational analysis of the whole exon 9 of PS-1. Upon the screening of a Spanish sample of early onset familial Alzheimer disease cases, we have found a novel mutation in the PS-1 gene. The mutation (a T to G transition) results in a change of the amino acid at position 282 of the presenilin protein from leucine to arginine. This mutation is located in the hydrophobic domain number 7 (exon 9) close to the site of physiological cleavage processing. The average of onset of the affected members of this family is 43 ± 5 years, and the average age of exitus of affected members is 56 ± 3 years. The possibility to determine the specific pathologic mechanisms of this mutation is now open.  1998 Published by Elsevier Science Ireland Ltd. Keywords: Presenilin-1; Alzheimer’s disease; Mutation; Genes Four different genes have been described to be involved in Alzheimer’s disease (AD), the amyloid precursor protein (APP) gene in chromosome 21 [7], the apolipoprotein E (APOE) gene on chromosome 19 [19,20], the presenilin-1 (PS-1) gene on chromosome 14 [18] and the presenilin-2 (PS-2) gene on chromosome 1 [12]. In the majority of cases, AD appears as a sporadic disease, whereas in a significant minority which includes the most aggressive forms of the disease, AD is transmitted as an autosomal dominant trait. Mutations within APP, PS-1 and PS-2 genes have been found to cause early-onset AD, with PS-1 mutations accounting for the majority of autosomally transmitted familial AD cases. To date, more than 30 different muta- tions have been detected in the PS-1 gene ([2,3,10,18,21], reviewed in [8,9]). The pathogenic mutations of the PS-1 gene are very heterogeneous [3,4,8,9] and are responsible for most cases of early-onset autosomal dominant AD. Recent data showing an association of sporadic late-onset AD with an intronic PS-1 polymorphism of the gene suggest that PS-1 is a potential risk factor for late-onset AD [1,6,11,15,22]. In order to screen for mutations in the PS-1 gene, we have developed a method based on DGGE analysis (Aldudo et al., in preparation) followed by direct sequencing of the PCR products showing altered DGGE patterns. All the early-onset AD (EOAD) patients included in the study met the NINCDS-ADRDA criteria [14]. The whole exon 9 of PS-1, according to the exon number- ing described by Rogaev et al. [16], was PCR amplified from genomic DNA using intronic primers, one of which contained a 40 bp GC clamp. The primer sequences were: Ex9U-GC: GCclamp-CACCCATTTACAAGTTTAGC and Ex9L: TATCCTTCTCAAATACTT. The PCR products ob- tained from 60 EOAD cases were subjected to DGGE ana- lysis and an altered pattern corresponding to an heterozy- gous subject bearing a mutant allele was found (Fig. 1A). Subsequently the PCR products were subjected to direct Neuroscience Letters 240 (1998) 174–176 0304-3940/98/$19.00  1998 Published by Elsevier Science Ireland Ltd. All rights reserved PII S0304-3940(97)00950-6 * Corresponding author. Tel.: +34 1 3978415/71; fax: +34 3974870/ 4799; e-mail: fvaldivieso@cbm.uam.es