Exome sequencing in an Italian family with Alzheimer's disease points to a role for seizure-related gene 6 (SEZ6) rare variant R615H
ALZHEIMERS RESEARCH & THERAPY
Authors: Paracchini, Lara; Beltrame, Luca; Boeri, Lucia; Fusco, Federica; Caffarra, Paolo; Marchini, Sergio; Albani, Diego; Forloni, Gianluigi
Abstract
Background: The typical familial form of Alzheimer's disease (FAD) accounts for about 5% of total Alzheimer's disease (AD) cases. Presenilins (PSEN1 and PSEN2) and amyloid- (A4) precursor protein (APP) genes carry all reported FAD-linked mutations. However, other genetic loci may be involved in AD. For instance, seizure-related gene 6 (SEZ6) has been reported in brain development and psychiatric disorders and is differentially expressed in the cerebrospinal fluid of AD cases. Methods: We describe a targeted exome sequencing analysis of a large Italian kindred with AD, negative for PSEN and APP variants, that indicated the SEZ6 heterozygous mutation R615H is associated with the pathology. Results: We overexpressed R615H mutation in H4-SW cells, finding a reduction of amyloid peptide A(1-42). Sez6 expression decreased with age in a mouse model of AD (3xTG-AD), but independently from transgene expression. Conclusions: These results support a role of exome sequencing for disease-associated variant discovery and reinforce available data on SEZ6 in AD models.
Systematic genetic study of Alzheimer disease in Latin America: Mutation frequencies of the amyloid beta precursor protein and presenilin genes in Colombia
AMERICAN JOURNAL OF MEDICAL GENETICS
Authors: Arango, D; Cruts, M; Torres, O; Backhovens, H; Serrano, ML; Villareal, E; Montanes, P; Matallana, D; Cano, C; Van Broeckhoven, C; Jacquier, M
Abstract
Nearly all mutations in the presenilin 1 (PSEN1), presenilin 2 (PSEN2), and amyloid beta precursor protein (APP) genes lead to early-onset Alzheimer disease (EOAD, onset age at or before 65 years). In order to assess the genetic contribution of these genes in a series of Colombian AD cases, we performed a systematic mutation analysis in 11 autosomal dominant, 23 familial, and 42 sporadic AD patients (34% with age of onset less than or equal to 65 years). No APP missense mutations were identified. In three autosomal dominant cases (27.2%), two different PSEN1 missense mutations were identified. Both PSEN1 mutations are missense mutations that occurred in early-onset autosomal AD cases: an I143T mutation in one case (onset age 30 years) and an E280A mutation in two other cases (onset ages 35 and 42 years). In addition, a novel PSEN1 V94M mutation was present in one early-onset AD case without known family history (onset age 53 years) and absent in 53 controls. The E318G polymorphism was present in five AD cases and absent in controls. In PSEN2, two different silent mutations were detected, including one not reported elsewhere (P129). The majority of the Colombian AD cases, predominantly late-onset, were negative for PSEN and APP mutations. (C) 2001 Wiley-Liss, Inc.