Mitochondrial DNA Variants Mediate Energy Production and Expression Levels for CFH, C3 and EFEMP1 Genes: Implications for Age-Related Macular Degeneration

Mitochondrial DNA Variants Mediate Energy Production and Expression Levels for CFH, C3 and EFEMP1 Genes: Implications for Age-Related Macular Degeneration M. Cristina Kenney 1 *, Marilyn Chwa 1 , Shari R. Atilano 1 , Janelle M. Pavlis 1 , Payam Falatoonzadeh 1 , Claudio Ramirez 1 , Deepika Malik 1 , Tiffany Hsu 1 , Grace Woo 1 , Kyaw Soe 1 , Anthony B. Nesburn 1,2 , David S. Boyer 3 , Baruch D. Kuppermann 1 , S. Michal Jazwinski 4 , Michael V. Miceli 4 , Douglas C. Wallace 5 , Nitin Udar 1 1 Gavin Herbert Eye Institute, University of California Irvine, Irvine, California, United States of America, 2 Cedars-Sinai Medical Center, Los Angeles, California, United States of America, 3 Retina-Vitreous Associates Medical Group, Beverly Hills, California, United States of America, 4 Tulane Center for Aging and Department of Medicine, Tulane University, New Orleans, Louisiana, United States of America, 5 Children’s Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America Abstract Background: Mitochondrial dysfunction is associated with the development and progression of age-related macular degeneration (AMD). Recent studies using populations from the United States and Australia have demonstrated that AMD is associated with mitochondrial (mt) DNA haplogroups (as defined by combinations of mtDNA polymorphisms) that represent Northern European Caucasians. The aim of this study was to use the cytoplasmic hybrid (cybrid) model to investigate the molecular and biological functional consequences that occur when comparing the mtDNA H haplogroup (protective for AMD) versus J haplogroup (high risk for AMD). Methodology/Principal Findings: Cybrids were created by introducing mitochondria from individuals with either H or J haplogroups into a human retinal epithelial cell line (ARPE-19) that was devoid of mitochondrial DNA (Rho0). In cybrid lines, all of the cells carry the same nuclear genes but vary in mtDNA content. The J cybrids had significantly lower levels of ATP and reactive oxygen/nitrogen species production, but increased lactate levels and rates of growth. Q-PCR analyses showed J cybrids had decreased expressions for CFH, C3, and EFEMP1 genes, high risk genes for AMD, and higher expression for MYO7A, a gene associated with retinal degeneration in Usher type IB syndrome. The H and J cybrids also have comparatively altered expression of nuclear genes involved in pathways for cell signaling, inflammation, and metabolism. Conclusion/Significance: Our findings demonstrate that mtDNA haplogroup variants mediate not only energy production and cell growth, but also cell signaling for major molecular pathways. These data support the hypothesis that mtDNA variants play important roles in numerous cellular functions and disease processes, including AMD. Citation: Kenney MC, Chwa M, Atilano SR, Pavlis JM, Falatoonzadeh P, et al. (2013) Mitochondrial DNA Variants Mediate Energy Production and Expression Levels for CFH, C3 and EFEMP1 Genes: Implications for Age-Related Macular Degeneration. PLoS ONE 8(1): e54339. doi:10.1371/journal.pone.0054339 Editor: Walter Lukiw, Louisiana State University Health Sciences Center, United States of America Received October 1, 2012; Accepted December 10, 2012; Published January 24, 2013 Copyright: s 2013 Kenney et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Funding provided by The Discovery Eye Foundation www.discoveryeye.org, Lincy Foundation lincyinstitute.unlv.edu/lincy.html, Beckman Macular Research Initiative www.beckmanmacular.org, The Henry Guenther Foundation, Polly and Michael Smith Foundation, Research to Prevent Blindness Foundation www.rpbusa.org, and the National Institute on Aging (AG006168). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: mkenney@uci.edu specific SNP variants that have accumulated over tens of thousands of years and correspond to different geographic populations of the world. The H haplogroup is the most common European haplogroup, while the J haplogroup originates from the Northern European region and is defined by SNP variants that are associated with heat production as an adaptation to colder climates [4]. The mtDNA plays an important role in aging and diseases [4– 6]. Specific haplogroups are associated with a variety of eye diseases including age-related macular degeneration (AMD) [7– 10], diabetic retinopathy [11], pseudoexfoliation glaucoma [12,13], primary open-angle glaucoma [14], keratoconus [15], multiple sclerosis-related optic neuritis [16,17], and Leber Introduction Mitochondria provide critical cellular energy using the tricar- boxylic acid (TCA) cycle, oxidative phosphorylation (OXPHOS), and beta-oxidation of fatty acids for metabolism, cell division, production of reactive oxygen species (ROS), and apoptosis. Human mitochondrial (mt) DNA forms a circle of double stranded DNA with 16,569 nucleotide pairs. The non-coding mtDNA Dloop contains 1121 nucleotides and is important for replication and transcription. The coding region of mtDNA encodes for 37 genes including 13 protein subunits essential for OXPHOS, 2 ribosomal RNAs, and 22 transfer RNAs [1–3]. The mtDNA can be categorized into haplogroups that are defined by a set of PLOS ONE | www.plosone.org January 2013 | Volume 8 | Issue 1 | e54339