The role of mitochondrial haplogroups in glaucoma: a study in an Arab population

Purpose: Glaucoma prevalence can vary geographically and ethnically, which suggests that a genetic element could play a significant role. Studies investigating the role of various mitochondrial haplogroups in the pathogenesis of glaucoma are scarce. Methods: We compared the prevalence of different mitochondrial haplogroups in 107 glaucoma patients (49 primary open-angle glaucoma, POAG; 29 primary angle-closure glaucoma, PACG; and 29 pseudoexfoliation glaucoma, PEG) and 552 maternally unrelated normal controls. All patients and controls were Saudi Arabs. Results: There was no statistically significant difference between patients and controls for all mitochondrial haplogroups tested except for PACG patients with mitochondrial haplogroup preHV1 (odds ratio=4.9; 95% CI 2.3 – 10.5; p=0.00002). Conclusions: Patients with preHV1 mitochondrial haplogroups are at higher risk of developing PACG. However, our study group is relatively small and further studies with more patients in other populations are needed to confirm this interesting finding. During evolution, several mutations have accumulated in mitochondrial DNA (mtDNA), representing specific single nucleotide polymorphisms (SNPs), allowing human populations to be categorized into various mtDNA haplogroups. In certain populations, these haplogroups were found to confer resistance against type 2 diabetes [1], influence energy dependent processes such as sperm motility and the risk of developing late onset neurodegenerative diseases [2], and contribute to the development of various types of cancer [3-7], Parkinson disease [8], and multiple sclerosis [9]. Glaucoma prevalence can vary by geography and by ethnicity [10-13], suggesting that a genetic element could play a significant role. In the western world, in predominantly Caucasian groups for instance, primary open-angle glaucoma (POAG) is the most commonly encountered adult onset type of glaucoma [14] while primary angle-closure glaucoma (PACG) has been reported much more frequently in Asiatic populations [15-17]. Pseudoexfoliation glaucoma (PEG) has also demonstrated wide prevalence variation around the world [13].