Hakan GÜRKAN, Sadık Altan ÖZAL, Haluk ESGİN

Results of Mitochondrial DNA Sequence Analysis in Patients with Clinically Diagnosed Leber’s Hereditary Optic Neuropathy

Objective: To investigate possible mitochondrial DNA (mtDNA) mutations in patients with Leber's hereditary optic neuropathy (LHON) in order to provide a precise diagnosis and genetic counseling. Material and Methods: Between 1982 and 2007, ten patients were clinically diagnosed with LHON and six of these patients agreed to be involved in this study. Six healthy individuals were also included as a control group. mtDNA was isolated from peripheral blood samples and polymerase chain reaction and mtDNA sequence analysis were performed. Results: In one of the six patients, a homoplasmic mutant m.11778G&gt;A mutation was detected. All of the clinically diagnosed LHON patients and the control groups had the m.14212C&gt;T and m.14580G&gt;A single nucleotide polymorphisms (SNPs). The m.11719A&gt;G SNP was detected in three of six patients and four of the controls. Two of the six patients had the m.3197T&gt;C SNP and, in addition, the m.14258G&gt;A SNP was found in one of these two patients, while neither of these mutations were present in the control group. Conclusion: The clinical diagnosis of LHON could be supported by molecular genetics only in one patient by the detection of one mutation. The m.3197T&gt;C and m.14258G&gt;A SNPs should be considered as potential mtDNA mutations due to the fact that they were detected in the patient group. These mutations should be investigated further in large case groups for suspected gene loci that could lead to optic neuropathy. Turkish Anahtar Kelimeler: Leber herediter optik nöropatisi, ailevi optik atrofi, mitokondrial DNA, Mıtokondrial DNA mutasyonları tek nükleotid polimorfizmi Amaç: Klinik olarak Leber'in Herediter Optik Nöropatisi (LHON) tanısı alan hastalarda, kesin tanı ve genetik danışmanlık verilebilmesi için olası mitokondriyal DNA mutasyonlarının araştırılması. Gereç ve Yöntemler: 1982-2007 yılları arasında klinik olarak LHON tanısı alan 10 hasta kliniğimize davet edildi. Bütün olgularda rutin oftalmolojik muayeneden sonra alınan periferik venöz kan örneklerinden mitokondriyal DNA ayrıştırılarak, polimeraz zincir reaksiyonu (PCR) ve mitokondriyal DNA dizi analizi yapıldı. Bulgular: 6 hastadan birinde Homozigot mutant olarak m.11778G&gt;A tek nükleotid değişimi (SNP) saptandı. 12 olgunun hepsinde m.14212C&gt;T ve m.14580G&gt;A SNP bulundu. 6 hastanın üçünde saptadığımız m.11719A&gt;G SNP, aynı zamanda kontrol grubundaki 4 kişide de saptandı. 6 hastanın ikisinde m.3197T&gt;C SNP ve bunlardan birinde ayrıca m.14258G&gt;A SNP bulunurken bu SNP'lerin hiçbirine kontrol grubunda rastlanmadı. Sonuç: Klinik olarak LHON tanısı alan olgularımızdan sadece birinde bilinen mutasyonlardan biri saptanarak klinik tanı moleküler genetik olarak da desteklendi. m.14258G&gt;A SNP'nin optik nöropatiye yol açabilecek olası mitokondriyal DNA mutasyonu olabileceği öngörüsündeyiz. Bu hipotezimizin kesinlik kazanabilmesi için olgu ve kontrol grubu sayısının arttırılarak çalışılmasına ihtiyaç vardır.

Keywords:

: Leber’s hereditary optic neuropathy, familial optic atrophy mitochondrial DNA, mitochondrial DNA mutations, single nucleotide polymorphism,

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Wallace DC, Singh G, Lott MT, Hodge JA, Schurr TG, Lezza AM, et al. Mitochondrial DNA mutation associated with Leber’s he- reditary optic neuropathy. Science 1988;242:1427-30. [CrossRef]
Howell N. LHON and other optic nerve atrophies: the mitochon- drial connection. Dev Ophthalmol 2003;37:94-108. [CrossRef]
MITOMAP. A human mitochondrial genome database. A com- pendium of polymorphisms and mutations of the human mito- chondrial DNA. www.mitomap.org.
Mackey D, Howell N. A variant of Leber hereditary optic neu- ropathy characterised by recovery of vision and by an usual mito- chondrial genetic etiology. Am J Hum Genet 1992;51:1218-28.
Man PYW, Turnbull DM, Chinnery PF. Leber hereditary optic neu- ropathy. J Med Genet 2002;39:162-9. [CrossRef]
Dogulu CF, Kansu T, Seyrantepe V, Ozguc M, Topaloglu H, Johns DR. Mitochondrial DNA analysis in Turkısh Leber’s hereditary op- tic neuropathy population. Eye(Lond) 2001;15:183-8. [CrossRef]
Harding AE, Sweeney MG, Govan GG, Riordan-Eva P. Pedigree analysis in Leber hereditary optic neuropathy families with a pathogenic mtDNA mutation. Am J Hum Genet 1995;57:77-86.
Zhou X, Zhang H, Zhao F, Ji Y, Tong Y, Zhang J, et al. Very high penetrance and occurrence of Leber’s hereditary optic neuropa- thy in a large Han Chinese pedigree carrying the ND4 G11778A mutation. Mol Genet Metab 2010;100:379-84. [CrossRef]
Johns DR, Neufeld MJ. Cytocrome b mutations in Leber he- reditary optic neuropathy. Biochem Biophys Res Commun 1991;181:1358-64. [CrossRef]
Brown MD, Yang CC, Trounce I, Torroni A, Lott MT, Wallace DC. A mitochondrial DNA variant, identified in Leber hereditary optic neuropathy patients, which extends the amino acid sequence of cytochrome c oxidase subunit I. Am J Hum Genet 1992;51:378-85.
Brown MD, Wallace DC. Spectrum of mitochondrial DNA mu- tations in Leber’s hereditary optic neuropathy. Clin Neurosci 1994;2:138-45.
Herrnstadt C, Elson LJ, Fahy E, Preston G, Turnbull DM, An- derson C, et al. Reduced-median-network analysis of complete mitochondrial DNA coding-region sequences for the major African, Asian, and European haplogroups. Am J Hum Genet 2002;70:1152-71. [CrossRef]
Fraumene C, Belle EM, Castrì L, Sanna S, Mancosu G, Cosso M, et al. High resolution analysis and phylogenetic network con- struction using complete mtDNA sequences in sardinian genetic isolates. Mol Biol Evol 2006;23:2101-11. [CrossRef]
Kivisild T, Shen P, Wall DP, Do B, Sung R, Davis K, et al. The role of selection in the evolution of human mitochondrial genomes. Genetics 2006;172:373-87. [CrossRef]
Achilli A, Perego UA, Bravi CM, Coble MD, Kong QP, Woodward SR, et al. The phylogeny of the four pan-American MtDNA hap- logroups: implications for evolutionary and disease studies. PLoS One 2008;3:e1764.
Roostalu U, Kutuev I, Loogväli EL, Metspalu E, Tambets K, Reidla M, et al. Origin and expansion of haplogroup H, the dominant human mitochondrial DNA lineage in West Eurasia: the Near Eastern and Caucasian perspective. Mol Biol Evol 2007;24:436-48. [CrossRef]