Allelic association at the D14S43 locus in early onset Alzheimer's disease. French Alzheimer's Disease Collaborative Study Group

T/G polymorphism at intron 9 of presenilin 1 gene is associated with, but not responsible for sporadic late-onset Alzheimer's disease in Japanese population

To investigate whether presenilin 1 (PS1) gene, a major causative gene of familial early-onset Alzheimer's disease (AD), also contributes to the etiology of sporadic AD, we evaluated associations between Japanese AD and polymorphisms located at 14q24.3. While the D14S43 and FOS loci showed no association with either early- or late-onset AD, late-onset AD carrying no APOE-epsilon4 allele was associated with the G allele of the T/G polymorphism located at intron 9 of the PS1 gene (P = 0.016). Considering another study showing a positive association between AD and the T allele, this polymorphism is associated with, but not responsible for sporadic late-onset Alzheimer's disease.

Evidence for apolipoprotein E epsilon 4 association in early-onset Alzheimer's patients with late-onset relatives

Recently several reports have extended the apolipoprotein E (APOE) epsilon 4 association found in late-onset Alzheimer's disease (LOAD) patients to early-onset (EO) AD patients. We have studied this question in a large population of 119 EOAD patients (onset < or = 60 years) in which family history was carefully assessed and in 109 controls. We show that the APOE epsilon 4 allele frequency is increased only in the subset of patients who belong to families where LOAD secondary cases are present. Our sampling scheme permits us to demonstrate that for an individual, bearing at least one epsilon 4 allele increases both the risk of AD before age 60 and the probability of belonging to a family with late-onset affected subjects. Our results suggest that a subset of EOAD cases shares a common determinism with LOAD cases.

The NACP/synuclein gene: chromosomal assignment and screening for alterations in Alzheimer disease

The major component of the vascular and plaque amyloid deposits in Alzheimer disease is the amyloid beta peptide (A beta). A second intrinsic component of amyloid, the NAC (non-A beta component of amyloid) peptide, has recently been identified, and its precursor protein was named NACP. A computer homology search allowed us to establish that the human NACP gene was homologous to the rat synuclein gene. We mapped the NACP/synuclein gene to chromosome 4 and cloned three alternatively spliced transcripts in lymphocytes derived from a normal subject. We analyzed by RT-PCR and direct sequencing the entire coding region of the NACP/synuclein gene in a group of patients with familial early onset Alzheimer disease. No mutation was found in 26 unrelated patients. Further studies are required to investigate the implication of the NACP/synuclein gene in Alzheimer disease.