Mitochondrial DNA haplogroups confer differences in risk for age-related macular degeneration: a case control study

Abstract

Background: Age-related macular degeneration (AMD) is the leading cause of vision loss in elderly, Caucasian populations. There is strong evidence that mitochondrial dysfunction and oxidative stress play a role in the cell death found in AMD retinas. The purpose of this study was to examine the association of the Caucasian mitochondrial JTU haplogroup cluster with AMD. We also assessed for gender bias and additive risk with known high risk nuclear gene SNPs, ARMS2/LOC387715 (G > T; Ala69Ser, rs10490924) and CFH (T > C; Try402His, rs1061170).

Methods: Total DNA was isolated from 162 AMD subjects and 164 age-matched control subjects located in Los Angeles, California, USA. Polymerase chain reaction (PCR) and restriction enzyme digestion were used to identify the J, U, T, and H mitochondrial haplogroups and the ARMS2-rs10490924 and CFH-rs1061170 SNPs. PCR amplified products were sequenced to verify the nucleotide substitutions for the haplogroups and ARMS2 gene.

Results: The JTU haplogroup cluster occurred in 34% (55/162) of AMD subjects versus 15% (24/164) of normal (OR = 2.99; p = 0.0001). This association was slightly greater in males (OR = 3.98, p = 0.005) than the female population (OR = 3.02, p = 0.001). Assuming a dominant effect, the risk alleles for the ARMS2 (rs10490924; p = 0.00001) and CFH (rs1061170; p = 0.027) SNPs were significantly associated with total AMD populations. We found there was no additive risk for the ARMS2 (rs10490924) or CFH (rs1061170) SNPs on the JTU haplogroup background.

Conclusions: There is a strong association of the JTU haplogroup cluster with AMD. In our Southern California population, the ARMS2 (rs10490924) and CFH (rs1061170) genes were significantly but independently associated with AMD. SNPs defining the JTU mitochondrial haplogroup cluster may change the retinal bioenergetics and play a significant role in the pathogenesis of AMD.

Figure 1

Schematic of circular mtDNA showing SNPs that define the H, J, T and U haplogroups. Cyt B, Cytochrome B; ND, NADH dehydrogenase; CO, Cytochrome c oxidase; ATPase, ATP synthase; D-loop, non-coding region between 16024 and 576.

Figure 2

Sequencing and restriction enzyme digestion of the ARMS2-rs10490924 SNP. Panel: Left – Sequence chromatogram of the GG homozygote, GT heterozygote and TT homozygote of the ARMS2-rs10490924 SNP. Right - 1.5% agarose gel showing the single lower band representing GG and the single higher band being TT. The double band represents heterozygous GT after PCR and digestion with PvuII. M = marker.