F175S change and a novel polymorphism in presenilin-1 gene in late-onset familial Alzheimer's disease.

We analyzed at the molecular level with presenilin-1 (PS-1) and apolipoprotein E (apoE) genotyping the affected subjects and asymptomatic relatives of an Italian family with several members affected by late-onset familial Alzheimer's disease (AD). The screen for PS-1 gene mutations revealed a novel missense substitution phenylalanine 175 to serine in 1 of the affected individuals and 2 asymptomatic sons of the patient. This change was not found in other relatives of this family, as well as in 60 individuals with sporadic late-onset AD and 40 normal controls. Furthermore, a GG/TT substitution in the 3' end of intron 6 at the boundary with exon 7 was found in all relatives of the second and third generations of this family. All the affected relatives were female homo- or heterozygotes for apoE epsilon4 allele. This study provides evidence that a PS-1 gene missense change does not necessarily associate with early-onset disease, and can occur in single cases affected by late-onset disease.