Analysis of the disease risk locus DXS1047 polymorphism in Brazilian Alzheimer patients

Alzheimer's disease (AD) is a disorder characterized by a progressive deter ioration in memory and other cognitive functions. Four genes associated wit h early onset AD have been identified(1-5) but familial AD is rare.(6) The majority of late onset AD (LOAD) is caused by a complex inheritance with se veral genes interacting with environmental factors. The epsilon 4 allele of the apolipoprotein E (APOE) gene has been reported worldwide as a risk fac tor associated with LOAD.(7-10) Th, short variant of a polymorphism in the transcriptional region of the serotonin transporter gene (5-HTTLPR) was ana lyzed in several psychiatric conditions(11-15) and found to be more frequen tly associated with European(16) and Brazilian LOAD patients,(17,18) Recent ly, allelic associations with LOAD were reported for five other loci,(19,20 ) the most significant for one X-linked 202-bp allele, at the DXS1047 locus . We have analyzed this locus in Brazilian LOAD patients and observed that the 202-bp allele was not significantly more frequent among patients. In co ntrast, two other alleles (200 bp and 208 bp) were less frequent among AD m ale patients than in controls, confirming the importance of replicating ass ociation studies in different populations.