Analysis of genetic polymorphisms in the transforming growth factor-beta1 gene and the risk of Alzheimer's disease.
Alzheimer's disease (AD) is a complex disease involving several genetic and environmental components. Genetic studies have yet to identify all the genes involved in the pathogenesis of AD. Transforming growth factor-beta1 (TGF-beta1) is a candidate gene for AD. It is a multifunctional cytokine whose overexpression has been shown to promote the deposition of amyloid-beta peptide. The goal of this study was to investigate the association of three polymorphisms in TGF-beta1 with the risk of AD. Two of the polymorphisms are located in the 5' region at positions -800 (G-->A) and -509 (C-->T), and the third is in exon 5 at codon 263 (Thr-->Ile). We screened DNA samples from 428 sporadic, late-onset patients and 421 controls by PCR-based assays. There was no statistically significant difference in genotype or allele frequency distributions between cases and controls for the -800 or codon 263 polymorphisms (P=0.38 and P=0.60, respectively). The overall genotype distribution at the -509 site was significantly different between cases and controls. (P=0.017). The frequency of the -509/TT genotype was significantly higher in AD patients than controls (P=0.015). We further tested whether this polymorphism may alter the regulation of the TGF-beta1 gene using dual luciferase reporter assay. We subcloned the 5' flanking region, which contained the -509 C/T polymorphic sites, in front of the firefly luciferase reporter gene in pGL-3 basic vector and co-transfected with the pRL-CMV vector containing Renilla luciferase gene as a control for transfection efficiency in COS-1 cells. The activity of each promoter allele was directly measured by the ratio of firefly luciferase activity to Renilla luciferase activity. The -509 T allele was associated with marginally higher transcriptional activity of TGF-beta compared with the -509 C allele (P=0.051). These data suggest that the -509 polymorphism of TGF-beta1 may be modestly associated with the risk of AD. However, these data should be interpreted with caution as the differences associated with the -509 alleles in both the genetic association and the transfection studies were modest.
Luedecking
E K
EK
Department of Human Genetics, Graduate School of Public Health, University of Pittsburgh, PA 15261, USA.
DeKosky
S T
ST
Mehdi
H
H
Ganguli
M
M
Kamboh
M I
MI
D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D000544:Alzheimer Disease / Q000209:etiology / Q000235:genetics* / Q000276:immunology; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D017931:DNA Primers / Q000235:genetics; D005260:Female; D005787:Gene Frequency; D017930:Genes, Reporter; D006801:Humans; D008156:Luciferases / Q000235:genetics; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D012307:Risk Factors; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000235:genetics*
D017931:DNA Primers; D016212:Transforming Growth Factor beta; D008156:Luciferases