You are here

Article Text

Article menu

This article has a correction. Please see:

Download PDFPDF

Electronic letters
Mitochondrial DNA haplogroup distribution within Leber hereditary optic neuropathy pedigrees
Free
  1. P Y W Man1,
  2. N Howell2,
  3. D A Mackey3,
  4. S Nørby4,
  5. T Rosenberg5,
  6. D M Turnbull1,
  7. P F Chinnery1
  1. 1Department of Neurology, The Medical School, University of Newcastle Upon Tyne, UK
  2. 2Mitokor, San Diego, CA, USA
  3. 3CERA, Royal Victorian Eye and Ear Hospital, Melbourne, Australia
  4. 4Institute of Forensic Medicine, University of Copenhagen, Denmark
  5. 5Gordon Norrie Centre for Genetic Eye Diseases, National Eye Clinic for the Visually Impaired, Hellerup, Denmark
  1. Correspondence to:
 Dr P F Chinnery
 Department of Neurology, The Medical School, University of Newcastle Upon Tyne, UK; p.f.chinneryncl.ac.uk

http://dx.doi.org/10.1136/jmg.2003.011247

Statistics from Altmetric.com

    Request Permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

    Leber hereditary optic neuropathy (LHON; OMIM #535000) is a mitochondrial genetic disease that causes blindness in young adults, with an estimated minimum prevalence of 3.2 per 100 000 in the north east of England.1 It classically presents as bilateral subacute loss of central vision due to the focal neurodegeneration of the retinal ganglion cell layer. Over 95% of cases are principally due to one of three “primary” mtDNA point mutations: 3460G→A, 11778G→A, and 14484T→C, all of which involve genes that encode complex I subunits of the mitochondrial respiratory chain. However, less than ~50% of male and ~10% of female LHON carriers will develop the optic neuropathy.2,3 This marked incomplete penetrance and gender bias clearly indicates that additional genetic and/or environmental factors are required for the phenotypic expression of the pathogenic mtDNA mutations in LHON. However, these secondary factors remain poorly defined at the present time.

    There has recently been considerable interest in the possible role of the mtDNA background on the phenotypic expression of mitochondrial genetic disorders. The hypothesis is that on their own, some polymorphisms are selectively “neutral” but that in specific combinations, they act in a synergistic, deleterious manner with established pathogenic mtDNA mutations to increase the risk of disease expression or to produce a more severe clinical outcome.4 The following nucleotide substitutions are found at a higher frequency in LHON patients relative to controls:5–7 4216T→C, 4917A→G, 9804G→A, 9438G→A, 13708G→A, 15257G→A, and 15812G→A. Phylogenetic analysis has shown that 4216T→C, 13708G→A, 15257G→A, and 15812G→A all cluster on a specific mtDNA background, haplogroup J, which is one of the nine haplogroups that define populations of European ancestry.8,9 Several studies have subsequently found that LHON pedigrees that harbour the 11778G→A and 14484T→C mutations are apparently not randomly distributed along the phylogenetic tree, but tend to show a preferential association with haplogroup J (table 1). It has therefore been argued that these polymorphic variants interact with the primary mtDNA mutations, increasing the risk of visual loss among LHON carriers. However, the potential pathogenic role of these so-called “secondary” mtDNA mutations in LHON is still controversial. All the association studies published so far involved a relatively small number of pedigrees collected over a wide geographical area by centres with a specialist interest in LHON, thereby raising the possibility of ascertainment bias. To investigate further the presumed association between primary LHON mutations and haplogroup J, we determined the haplogroup distribution of a rigorously defined, population based LHON cohort from the north east of England, and carried out a systematic statistical review of the literature.

    View this table:
    Table 1

    Summary of haplogroup association studies in LHON

    Key points

    • Over 95% of Leber hereditary optic neuropathy (LHON) pedigrees harbour one of three mitochondrial DNA (mtDNA) point mutations: 3460G→A, 11778G→A, or 14484T→C. However, additional genetic and/or environmental factors influence the penetrance of the primary mtDNA mutations that cause focal degeneration of the optic nerve in LHON.

    • There is evidence that the mtDNA background could be relevant for the phenotypic expression of LHON.

    • We carried out a meta-analysis of 297 published LHON pedigrees and confirmed the strength of the association between one specific mtDNA lineage, haplogroup J, and two of the primary LHON mutations: 11778G→A (odds ratio (OR) = 3.48, 95% confidence interval (CI) 2.36 to 5.15) and 14484T→C (OR = 27.53, 95% CI 14.53 to 52.13), and confirmed the absence of an association with the 3460G→A mutation (OR = 1.29, 95% CI 0.57 to 2.90).

    • The most compelling explanation is that the risk of visual loss in LHON carriers with the 11778G→A and 14484T→C mutations is increased by haplogroup J, and by extension, one or more of the mtDNA polymorphisms that define this haplogroup.

    MATERIALS AND METHODS

    Study population

    Patients presenting with unexplained visual failure or suspected LHON within the north east of England were referred to the Northern Genetics Service based in Newcastle upon Tyne over the 12 year period from January 1990 to May 2002. Diagnostic mitochondrial genetic analysis was then carried out within the Mitochondrial Research Group of the Department of Neurology, University of Newcastle upon Tyne. This led to the identification of 15 genealogically distinct LHON pedigrees, confirmed by sequencing of the mtDNA D-loop region1 (table 2).

    View this table:
    Table 2

    Haplogroup distribution in the north east of England

    Haplogroup determination

    One member of each pedigree was analysed and the haplogroup was determined by restriction enzyme analysis of the relevant PCR amplified mtDNA fragment, as described previously.10 The haplogroup distribution of 179 normal controls from the north east of England had also been determined previously using the same protocol.11

    Systematic review

    Published studies that had analysed haplogroup distribution in LHON pedigrees were identified by searching the main electronic databases (MedLine and Web of Science) from 1988, when the first LHON mutation was reported.12 The keywords used in the search strategy were “optic atrophy”, “mitochondrial DNA”, “haplogroup”, and “phylogeny”. The reference lists of relevant papers were also assessed for the presence of additional studies not listed in these databases. Finally, the main investigators in the field of mitochondrial genetics were also contacted personally to obtain any unpublished data that might clarify some of their published results, especially if the raw data were not provided in the original paper.

    Study selection

    For the purpose of this review, studies (published or unpublished) were included only if sufficient data had been collected by the investigators to allow the haplogroup to be clearly deduced for their LHON pedigrees. In some of these studies, haplogroup status was not reported directly. However, pedigrees could still be grouped as being either J or non-J, as long as the polymorphic status at nucleotide positions 4216 and 13708 had been determined.9,10 As far as possible, we tried to ascertain that all included pedigrees were unrelated and of European extraction.

    Statistical analysis

    A meta-analysis was carried out using the Mantel-Haenszel method as implemented in the Cochrane Review Manager™ software (version 4.1). A fixed effect model was adopted given the lack of significant heterogeneity between the included studies (http://www.cochrane.de/cochrane/hbook.htm).

    RESULTS

    In our population based LHON cohort from the north east of England, there was a trend towards haplogroup J being over-represented in 11778G→A and 14484T→C pedigrees compared with our control population, but this was not statistically significant because of the small number of pedigrees involved (table 2). A total of 10 other haplogroup J association studies were identified through our search strategy (table 1). The main findings of our statisical meta-analysis are summarised graphically by a forest plot (fig 1).

    Figure 1
    Figure 1

    Meta-analysis of haplogroup J association studies. Comparison of (A) LHON 3460G→A v controls; (B) LHON 11778G→A v controls; (C) LHON14484T→C v controls.OR, odds ratio. An OR of 1.0 indicates that the prevalence of haplogroup J is the same in both LHON and controls; OR<1.0, under-represented; OR>1.0, over-represented. The size of each square is proportional to the amount of information provided by the study. The diamond shaped figure denotes the combined results for all the included trials.

    For the 3460G→A pedigrees, the prevalence of haplogroup J (7.8%) was not significantly different to that in normal controls (9.3%) (odds ratio (OR)=1.29 (95% CI 0.57 to 2.90)). Haplogroup J was moderately over-represented for the 11778G→A pedigrees (26.8% v only 9.3% in controls; OR=3.48; 95% CI 2.36 to 5.15). There was a strong association between the 14484T→C mutation and haplogroup J (OR=27.53; 95% CI, 14.53 to 52.13). Over 75% of the 14484T→C LHON pedigrees belong to haplogroup J, as against only ~11% of the control mtDNAs.

    DISCUSSION

    This meta-analysis confirms the reported association between two of the primary LHON mutations, 11778G→A and 14484T→C, and haplogroup J. This was particularly marked for 14484T→C, with pedigrees harbouring this mutation being ~30 times more likely to belong to this particular haplogroup than controls. While it is important to consider the possibility that these results are influenced by the method of ascertainment, particularly through a publication bias following the identification of the so-called “secondary” LHON mtDNA mutations in 1991, the magnitude of the association is so great that it seems unlikely that this can be the sole explanation. Moreover, our epidemiological study of LHON in a defined geographical region revealed the same trend towards a haplogroup J association, adding weight to our conclusion.

    How can we explain the association between mtDNA haplogroup J and the 11778G→A and 14484T→C mutations? It is conceivable that this could be due to an early founder effect, whereby the 11778G→A and 14484T→C mutations arose early in the evolution of haplogroup J, leading to its over-representation on that mitochondrial lineage. There is some evidence in support of this hypothesis in the Dutch population,13 but this cannot provide a complete explanation because all three primary LHON mutations have arisen multiple times on different mitochondrial backgrounds10 (see also the discussion in Howell et al13 and Brown et al14). Moreover, none of these mtDNA mutations has been found in the large sample of normal control mitochondrial genomes that belong to haplogroup J (for examples, see http://www.genpat.uu.se/mtDB/index.html). There are a number of other possible explanations for this haplogroup J association. This particular mtDNA haplogroup J appears to be associated with successful ageing,15 a high complex I activity in spermatozoa,16 and a lower risk of developing Parkinson’s disease,17 although the latter is still contentious.18 These putative “protective” effects of haplogroup J could confer a competitive advantage, leading to persistence of LHON mutations in the population, as has already been suggested,19 but it is difficult to see why this should be specific for the 11778G→A and 14484T→C LHON mutations only. Although a point of great debate, the most compelling explanation is that the risk of visual loss is increased by haplogroup J.

    If this mtDNA background does have a deleterious effect, it would be expected that haplogroup J should result in a more pronounced respiratory chain defect, and thus influence the phenotype of LHON. Cybrid cell lines carrying the 11778G→A mutation and haplogroup J were shown to have a lower oxygen consumption and a longer doubling time compared with cell lines with the 11778G→A mutation alone.20 However, a recently published study showed no difference in respiratory chain function between cybrid cell lines harbouring mtDNA from different haplogroups on the same nuclear genetic background.19 In vivo magnetic resonance spectroscopy in patients harbouring the 11778G→A mutation also failed to detect any deleterious effect in brain and skeletal muscle from haplogroup J.21 The influence of haplogroup J on the biochemical features of the 14484T→C mutation has not yet been determined. This result would be interesting in order to clarify the much stronger association of haplogroup J with 14484T→C compared with 11778G→A. However, these studies will require cautious interpretations, given that both in vitro and in vivo biochemical studies have produced conflicting results regarding the extent of respiratory chain dysfunction in LHON. There is currently no evidence that haplogroup J influences age of onset or final visual outcome in LHON, although this trend requires further confirmation in a larger LHON cohort.22 Haplogroup J is one of nine European specific haplogroups, and therefore it would also be expected that LHON should be more common in populations of European extraction. This hypothesis will be difficult to test, given the paucity of data regarding the prevalence of LHON in different ethnic groups, and potential confounding factors such as a population bottleneck.23

    The analysis presented here also provides strong statistically based evidence that there is no association between haplogroup J and the 3460G→A mtDNA mutation. This is a most intriguing finding, given the strong haplogroup affiliation for the two other primary LHON mutations. However, the 3460G→A mutation seems to behave differently in a number of ways. Firstly, 3460G→A is the LHON mutation most consistently associated with a significant biochemical complex I defect; secondly, compared with the 14484T→C mutation, it is associated with a poorer visual outcome; and thirdly, it is associated with a less prominent gender bias.24 This evidence suggests that 3460G→A is perhaps a “stronger” mutation—that is, less susceptible to the epistatic and epigenetic factors influencing the expression of the 14484T→C mutation and possibly the 11778G→A mutation.

    Based on our meta-analysis of all published and unpublished datasets, there seems to be little doubt that the 14484T→C mutation, and to a lesser extent the 11778G→A mutation, are over-represented in haplogroup J, but several additional questions remain unanswered. What is the combination of polymorphisms within haplogroup J that increases the risk of disease expression? Unfortunately, there are insufficient published data available to carry out haplogroup J sub-cluster analysis and explore further the differences reported in sub-clusters J1 and J2.10 Why should the 3460G→A mutation prove refractory to the mitochondrial genetic background? We have as yet no answer. Addressing these important issues will not only advance our understanding of LHON, but will also have broader relevance for other pathogenic mtDNA mutations.

    Acknowledgments

    This work was supported by the Wellcome Trust (P F Chinnery, D M Turnbull), the Medical Research Council (D M Turnbull), the Eierman Foundation (N Howell), and the PPP Healthcare Trust (P Y W Man). We wish to thank all the patients and their family members for their participation in this study, and the clinicians in the north of England who referred their patients for investigation. We are also grateful to S A Lynch, S McDonnell and G Ahearne for their work with LHON families. We are also indebted to the various investigators who kindly provided us with their unpublished haplogroup data.

    REFERENCES

    1. ↵
      Man PY, Griffiths PG, Brown DT, Howell N, Turnbull DM, Chinnery PF. The epidemiology of Leber hereditary optic neuropathy in the north east of England. Am J Hum Genet2003;72:333–9.
      OpenUrlCrossRefPubMedWeb of Science
    2. ↵
      Seedorff T. The inheritance of Leber’s disease: a geneological follow-up study. Acta Ophthalmol1985;63:135–45.
      OpenUrlPubMed
    3. ↵
      Riordan-Eva P, Harding AE. Leber’s hereditary optic neuropathy: the clinical relevance of different mitochondrial DNA mutations. J Med Genet1995;32:81–7.
      OpenUrlFREE Full Text
    4. ↵
      Chinnery PF, Howell N, Andrews RM, Turnbull DM. Mitochondrial DNA analysis: polymorphisms and pathogenicity. J Med Genet1999;36:505–10.
      OpenUrlAbstract/FREE Full Text
    5. ↵
      Johns DR, Berman J. Alternative simulataneous complex I mitochondrial DNA mutations in Leber’s hereditary optic neuropathy. Biochem Biophys Res Commun1991;174:1324–30.
      OpenUrlCrossRefPubMedWeb of Science
    6. ↵
      Johns DR, Neufeld MJ. Cytochrome b mutations in Leber hereditary optic neuropathy. Biochem Biophys Res Commun1991;181:1358–64.
      OpenUrlCrossRefPubMedWeb of Science
    7. ↵
      Johns DR, Neufeld MJ. Cytochrome c oxidase mutations in Leber hereditary optic neuropathy. Biochem Biophys Res Commun1993;196:810–15.
      OpenUrlCrossRefPubMedWeb of Science
    8. ↵
      Brown MD, Torroni A, Reckord CL, Wallace DC. Phylogenetic analysis of Leber’s hereditary optic neuropathy mitochondrial DNAs indicates multiple independent occurrences of the common mutations. Hum Mutat1995;6:311–25.
      OpenUrlCrossRefPubMedWeb of Science
    9. ↵
      Torroni A, Huoponen K, Francalacci P, Petrozzi M, Morelli L, Scozzari R, Obinu D, Savontaus ML, Wallace DC. Classification of European mtDNAs from an analysis of three European populations. Genetics1996;144:1835–50.
      OpenUrlAbstract/FREE Full Text
    10. ↵
      Torroni A, Petrozzi M, D’Urbano L, Sellitto D, Zeviani M, Carrara F, Carducci C, Leuzzi V, Carelli V, Barboni P, De Negri A, Scozzari R. Haplotype and phylogenetic analyses suggest that one European-specific mtDNA background plays a role in the expression of Leber hereditary optic neuropathy by increasing the penetrance of the primary mutations 11778 and 14484. Am J Hum Genet1997;60:1107–21.
      OpenUrlPubMedWeb of Science
    11. ↵
      Chinnery PF, Taylor GA, Howell N, Andrews RM, Morris CM, Taylor RW, McKeith IG, Perry RH, Edwardson JA, Turnbull DM. Mitochondrial DNA haplogroups and susceptibility to AD and dementia with Lewy bodies. Neurology2000;55:302–4.
      OpenUrlAbstract/FREE Full Text
    12. ↵
      Wallace DC, Singh G, Lott MT, Hodge JA, Schurr TG, Lezza AM, Elsas LJ 2nd, Nikoskelainen EK. Mitochondrial DNA mutation associated with Leber’s hereditary optic neuropathy. Science1988;242:1427–30.
      OpenUrlAbstract/FREE Full Text
    13. ↵
      Howell N, Oostra RJ, Bolhuis PA, Spruijt L, Clarke LA, Mackey DA, Preston G, Herrnstadt C. Sequence analysis of the mitochondrial genomes from dutch pedigrees with Leber hereditary optic neuropathy. Am J Hum Genet2003;72:1460–9.
      OpenUrlCrossRefPubMedWeb of Science
    14. ↵
      Brown MD, Starikovskaya E, Derbeneva O, Hosseini S, Allen JC, Mikhailovskaya IE, Sukernik RI, Wallace DC. The role of mtDNA background in disease expression: a new primary LHON mutation associated with Western Eurasian haplogroup J. Hum Genet2002;110:130–8.
      OpenUrlCrossRefPubMedWeb of Science
    15. ↵
      De Benedictis G, Rose G, Carrieri G, De Luca M, Falcone E, Passarino G, Bonafe M, Monti D, Baggio G, Bertolini S, Mari D, Mattace R, Franceschi C. Mitochondrial DNA inherited variants are associated with successful aging and longevity in humans. FASEB J1999;13:1532–6.
      OpenUrlAbstract/FREE Full Text
    16. ↵
      Ruiz-Pesini E, Lapena AC, Diez-Sanchez C, Perez-Martos A, Montoya J, Alvarez E, Diaz M, Urries A, Montoro L, Lopez-Perez MJ, Enriquez JA. Human mtDNA haplogroups associated with a high or reduced spermatozoa motility. Am J Hum Genet2000;67:682–96.
      OpenUrlCrossRefPubMedWeb of Science
    17. ↵
      van der Walt JM, Nicodemus KK, Martin ER, Scott WK, Nance MA, Watts RL, Hubble JP, Haines JL, Koller WC, Lyons K, Pahwa R, Stern MB, Colcher A, Hiner BC, Jankovic J, Ondo WG, Allen FH Jr, Goetz CG, Small GW, Mastaglia F, Stajich JM, McLaurin AC, Middleton LT, Scott BL, Schmechel DE, Pericak-Vance MA, Vance JM. Mitochondrial polymorphisms significantly reduce the risk of Parkinson disease. Am J Hum Genet2003;72:804–11.
      OpenUrlCrossRefPubMedWeb of Science
    18. ↵
      Ross OA, McCormack R, Maxwell LD, Duguid RA, Quinn DJ, Barnett YA, Rea IM, El-Agnaf OM, Gibson JM, Wallace A, Middleton D, Curran MD. mt4216C variant in linkage with the mtDNA TJ cluster may confer a susceptibility to mitochondrial dysfunction resulting in an increased risk of Parkinson’s disease in the Irish. Exp Gerontol2003;38:397–405.
      OpenUrlCrossRefPubMedWeb of Science
    19. ↵
      Carelli V, Vergani L, Bernazzi B, Zampieron C, Bucchi L, Valentino M, Rengo C, Torroni A, Martinuzzi A. Respiratory function in cybrid cell lines carrying European mtDNA haplogroups: implications for Leber’s hereditary optic neuropathy. Biochim Biophys Acta2002;1588:7–14.
      OpenUrlPubMedWeb of Science
    20. ↵
      Vergani L, Martinuzzi A, Carelli V, Cortelli P, Montagna P, Schievano G, Carrozzo R, Angelini C, Lugaresi E. MtDNA mutations associated with Leber’s hereditary optic neuropathy: studies on cytoplasmic hybrid (cybrid) cells. Biochem Biophys Res Commun1995;210:880–8.
      OpenUrlCrossRefPubMedWeb of Science
    21. ↵
      Lodi R, Montagna P, Cortelli P, Iotti S, Cevoli S, Carelli V, Barbiroli B. ‘Secondary’ 4216/ND1 and 13708/ND5 Leber’s hereditary optic neuropathy mitochondrial DNA mutations do not further impair in vivo mitochondrial oxidative metabolism when associated with the 11778/ND4 mitochondrial DNA mutation. Brain2000;123:1896–902.
      OpenUrlAbstract/FREE Full Text
    22. ↵
      Oostra RJ, Bolhuis PA, Zorn-Ende I, de Kok-Nazaruk MM, Bleeker-Wagemakers EM. Leber’s hereditary optic neuropathy: no significant evidence for primary or secondary pathogenicity of the 15257 mutation. Hum Genet1994;94:265–70.
      OpenUrlCrossRefPubMedWeb of Science
    23. ↵
      Macmillan C, Johns TA, Fu K, Shoubridge EA. Predominance of the T14484C mutation in French-Canadian families with Leber hereditary optic neuropathy is due to a founder effect. Am J Hum Genet2000;66:332–5.
      OpenUrlCrossRefPubMed
    24. ↵
      Man PY, Turnbull DM, Chinnery PF. Leber hereditary optic neuropathy. J Med Genet2002;39:162–9.
      OpenUrlAbstract/FREE Full Text
    25. ↵
      Finnila S, Majamaa K. Phylogenetic analysis of mtDNA haplogroup TJ in a Finnish population. J Hum Genet2001;46:64–9.
      OpenUrlCrossRefPubMedWeb of Science
    26. ↵
      Mackey DA, Buttery RG. Leber hereditary optic neuropathy in Australia. Austr New Zealand J Med1992;20:177–84.
      OpenUrl
    27. ↵
      Johns DR, Heher KL, Miller NR, Smith KH. Leber’s hereditary optic neuropathy. Clinical manifestations of the 14484 mutation. Arch Ophthalmol1993;111:495–8.
      OpenUrlCrossRefPubMedWeb of Science
    28. ↵
      Hofmann S, Jaksch M, Bezold R, Mertens S, Aholt S, Paprotta A, Gerbitz KD. Population genetics and disease susceptibility: characterization of central European haplogroups by mtDNA gene mutations, correlation with D loop variants and association with disease. Hum Mol Genet1997;6:1835–46.
      OpenUrlAbstract/FREE Full Text
    29. ↵
      Lamminen T, Huoponen K, Sistonen P, Juvonen V, Lahermo P, Aula P, Nikoskelainen E, Savontaus ML. MtDNA haplotype analysis in Finnish families with Leber hereditary optic neuroretinopathy. Eur J Hum Genet1997;5:271–9.
      OpenUrlPubMedWeb of Science
    30. ↵
      Norby S, Saillard J, Magalhaes P, Schwartz M, Rosenberg T. The spectrum of pathogenic mutations and mtDNA haplogroups among Danish lineages manifesting Leber hereditary optic neuropathy. Am J Hum Genet1999;65:2219.
      OpenUrl
    View Abstract

    Linked Articles

    • Correction
      Correction
      BMJ Publishing Group Ltd
      Journal of Medical Genetics 2016; 53 493-493 Published Online First: 23 Jun 2016. doi: 10.1136/jmg.2003.011247corr1