A broad region of chromosome 10 (chr10) has engendered continued interest in the etiology of late-onset Alzheimer Disease (LOAD) from both linkage and candidate gene studies. However, there is a very extensive heterogeneity on chr10. We converged linkage analysis and gene expression data using the concept of genomic convergence that suggests that genes showing positive results across multiple different data types are more likely to be involved in AD. We identified and examined 28 genes on chr10 for association with AD in a Caucasian case-control dataset of 506 cases and 558 controls with substantial clinical information. The cases were all LOAD (minimum age at onset ≥ 60 years). Both single marker and haplotypic associations were tested in the overall dataset and 8 subsets defined by age, gender, ApoE and clinical status. PTPLA showed allelic, genotypic and haplotypic association in the overall dataset. SORCS1 was significant in the overall data sets (p=0.0025) and most significant in the female subset (allelic association p=0.00002, a 3-locus haplotype had p=0.0005). Odds Ratio of SORCS1 in the female subset was 1.7 (p<0.0001). SORCS1 is an interesting candidate gene involved in the Aβ pathway. Therefore, genetic variations in PTPLA and SORCS1 may be associated and have modest effect to the risk of AD by affecting Aβ pathway. The replication of the effect of these genes in different study populations and search for susceptible variants and functional studies of these genes are necessary to get a better understanding of the roles of the genes in Alzheimer disease.

Inflammation has long been suspected to play a role in the pathogenesis of age-related macular degeneration (AMD). Association of variants in the complement factor H (CFH) and complement factor B (CFB) genes has targeted the search for additional loci to the alternative complement cascade, of which C3 is a major component. Two non-synonymous coding polymorphisms within C3, R102G and L314P, have previously been strongly associated with increased risk. These variants are in strong linkage disequilibrium (LD), making the contribution of this locus to AMD even more difficult to ascertain. We sought to determine whether the C3 association resulted primarily from only one of these two variants or from a combined effect of both in 223 families and an independent dataset of 701 cases and 286 unrelated controls. The C3 polymorphisms were in strong LD (r(2) = 0.85), and both were associated in the family-based and case-control datasets (R102G genoPDT P = 0.02, case-control genotypic P = 0.004; L314P genoPDT P = 0.001, case-control genotypic P = 0.04). In conditional analyses in the case-control dataset, R102G remained associated with disease in the L314P risk allele carriers (P = 0.01), but there was no effect of L314P in the R102G risk allele carriers (P = 0.2). After adjusting for age, smoking, CFH Y402H, LOC387715 A69S, and CFB R32Q, the effect of R102G remained strong [P = 0.015, odds ratio = 1.55, 95% confidence interval 1.09 to 2.21, adjusted PAR(population attributable risk) = 0.17]. Therefore, while the strong LD between R102G and L314P makes it difficult to disentangle their individual effects on disease risk, the R102G polymorphism acting alone provides the best model for disease in our data.

The objective of this study was to determine if MTND2*LHON4917G (4917G), a specific non-synonymous polymorphism in the mitochondrial genome previously associated with neurodegenerative phenotypes, is associated with increased risk for age-related macular degeneration (AMD). A preliminary study of 393 individuals (293 cases and 100 controls) ascertained at Vanderbilt revealed an increased occurrence of 4917G in cases compared to controls (15.4% vs.9.0%, p = 0.11). Since there was a significant age difference between cases and controls in this initial analysis, we extended the study by selecting Caucasian pairs matched at the exact age at examination. From the 1547 individuals in the Vanderbilt/Duke AMD population association study (including 157 in the preliminary study), we were able to match 560 (280 cases and 280 unaffected) on exact age at examination. This study population was genotyped for 4917G plus specific AMD-associated nuclear genome polymorphisms in CFH, LOC387715 and ApoE. Following adjustment for the listed nuclear genome polymorphisms, 4917G independently predicts the presence of AMD (OR = 2.16, 95%CI 1.20–3.91, p = 0.01). In conclusion, a specific mitochondrial polymorphism previously implicated in other neurodegenerative phenotypes (4917G) appears to convey risk for AMD independent of recently discovered nuclear DNA polymorphisms.