A I716T mutation of amyloid precursor protein gene in familial Alzheimer′s disease

Objective To analyze the clinical presentation and explore potential mutation of pathogenic genes in a Chinese family with early-onset familial Alzheimer′ s disease (EOFAD). Methods The clinical features and the results of auxiliary examination were collected and analyzed. DNA was extracted from peripheral blood samples from 8 members of the EOFAD family as well as 20 patients with sporadic Alzheimer′s disease (SAD) and 50 healthy controls.By polymerase chain reaction and direct DNA sequencing, mutational analysis of presenilin 1(exons 3-12), presenilin 2(exons 1-12), and amyloid precursor protein (APP) genes (exons 16-17) was performed. Results Molecular genetic analysis revealed that 6 patients had a mutation of g. 275339T>C in exon 17 of APP gene, which caused ATC conversion to ACC, resulted in the amino acid substitution as Ile716Thr(I716T). Among them one was patient with dementia, the other five were clinically normal but under onset age.The same mutation was not found in the SAD patients and healthy controls. Conclusions We reported a novel I716T mutation in exon 17 of the APP gene in a Chinese EOFAD pedigree. This mutation probably promoted the pathogenesis of EOFAD in this Chinese pedigree, eventually resulting in dementia. Key words: Alzheimer disease; Amyloid beta-protein precursor; Gene; Mutation