The unique characteristics of Thai Leber hereditary optic neuropathy: analysis of 30 G11778A pedigrees

Leber hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral visual loss, and affects mostly young males. The most common mitochondrial DNA mutation responsible for LHON worldwide is G11778A. Despite different genetic backgrounds, which are believed to influence the disease expression, most features of LHON are quite common in different populations. However, there seem to be a few ethnic-specific differences. Analyses of our 30 G11778A LHON pedigrees in Thailand showed some characteristics different from those of Caucasians and Japanese. In particular, our pedigrees showed a lower male to female ratio of affected persons (2.6:1) and much higher prevalence of G11778A blood heteroplasmy (37% of the pedigrees contained at least one heteroplasmic G11778A individual). Heteroplasmicity seemed to influence disease manifestation in our patients but did not appear to alter the onset of the disease. The estimated overall penetrance of our G11778A LHON population was 37% for males and 13% for females. When each of our large pedigrees were considered separately, disease penetration varied from 9 to 45% between the pedigrees, and also varied between different branches of the same large pedigree. Survival analysis showed that the secondary LHON mutations G3316A and C3497T had a synergistic deleterious effect with the G11778A mutation, accelerating the onset of the disease in our patients.     

An unusual family with Leber''s hereditary optic neuropathy and facioscapulohumeral muscular dystrophy

We performed an observational prospective analysis to study the clinical characteristics as well as a molecular genetic analysis of 17 members of a Thai family who had visual loss and/or muscle weakness. Their blood mitochondrial DNA were examined for the presence of the G11778A Leber's hereditary optic neuropathy (LHON) mutation. Facioscapulohumeral muscular dystrophy (FSHD) DNA analysis was performed in four members who had visual loss. Of 17 family members, the eight members who had the 11778 LHON mutation were all from branch 'a'. Three of these eight members had FSHD with a 17-27-kb deletion of a tandem repeat in the 4q35 subtelomere, and two had been clinically diagnosed as FSHD. Four of six examined members in branch 'b' showed muscular dystrophy clinically diagnosed as FSHD. No correlation of blood DNA analysis between LHON and FSHD in affected members was found. We describe the first family with FSHD and G11778A LHON in which a mutation in mitochondrial DNA at nucleotide position 11778 of branch 'a' was found to be the origin of the mutation.     

Transmission of heteroplasmic G11778A in extensive pedigrees of Thai Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is characterized by the acute or subacute bilateral painless loss of central vision, predominantly in young males. G11778A is the most common mitochondrial DNA mutation responsible for the disease. Thirty-seven percent of our LHON pedigrees (which is a much higher prevalence than that generally found) carried heteroplasmic G11778A. Analyses of four large Thai LHON pedigrees spanning four to six generations strongly suggested that the transmission of the heteroplasmic G11778A mutation is under selective pressure in favour of the mutated allele and that heteroplasmy influences the disease expression.     

Mitochondrial DNA polymorphism in disease: a possible contributor to respiratory dysfunction

Intergenomic variation in the human mitochondrial genome wasexamined in 27 mtDNA sequences using a pairwise analysis technique.Analysis of 16 of these mtDNA sequences from patients with mitochondrialcystopathies Indicated a wide range between different mitochondrialgenes in the degree of nucleotide variation from the standardCambridge sequence. Mean complex I ploymorphic frequencelesin cytopathic (CPEO, MERRF, MELAS and LHON collecstively) patientsand in LHON pastients differed significantly from controls (P0.05,t).Total mean sequence divergence (mean number of divergingnucleotides between two sequences per 100 bp) over the entieremtDNA coding region was 0.21% for cytropathies (n = 16) as opposedto 0.18% for a control group (n = 4). Within the cytopathy group,the greatest pairwise divergence was observed in ND3 and ND6subunits of complex i (0.46 and 0.70% respectively) and themagnitude of specific gene divergences differed considerablyfrom those observed for the corresponding genes in the controlpopulation. The extent to which the Increassed vasriation inND3 and ND6 is a general phenomenon applicable to all subjectsrather than a finding specific to cytopathies cannot be statedwith certainty given the small congtrol group. Regardless asto which of these suggestions is correct, the possibility existsthat increased nucleotide variastion in certain mitochondrialND subunits may contribute to respiratory inefficiency througha cumulative effect of a series of polymorphisms of minor Individualmutagenic potential.     

Mitochondrial DNA haplogroup distribution in pedigrees of Southeast Asian G11778A Leber hereditary optic neuropathy.

To investigate the association of mitochondrial DNA (mtDNA) haplogroups and Leber hereditary optic neuropathy (LHON) in the Southeast Asian population, mtDNA haplogroup determination was performed by high-resolution restriction fragment length polymorphism in 42 patients with LHON who were carrying the G11778A mutation and in control subjects drawn from a Thai urban population unaffected by LHON. The patients with LHON were of Thai, Thai-Chinese, and Indian origin. Three mtDNA haplogroups, M, B*, and B, were found in LHON patients in a frequency similar to that in control subjects. mtDNA haplogroup F was found in none of the patients with LHON but was the second most common haplogroup in control subjects. The G11778A mutation must have arisen in our population independently from the mutation in Caucasians. In contrast to Caucasians, no specific mtDNA haplotype was associated with the patients with LHON in the Southeast Asian population. The mitochondrial polymorphisms that modify the expression of LHON in Southeast Asians could not be identified in this study. The lack of haplogroup F in our patients with LHON may indicate the protective effect of this haplogroup in the expression of this disorder.     

Proportion of 11778 mutant mitochondrial DNA and clinical expression in a thai population with leber hereditary optic neuropathy.

BACKGROUND: The proportion of mutant mtDNA in blood has been found to correlate with the frequency of visual loss in cases with mtDNA mutations associated with Leber hereditary optic neuropathy (LHON), especially in men. We sought to determine this correlation in a Thai population of LHON. METHODS: Densitometric quantification of blood mtDNA with the 11,778 LHON mutation in 137 symptomatic cases and their asymptomatic maternal relatives in 30 Asian pedigree families was performed. Asymptomatic maternal relatives under the age of 16 years were excluded. The visual outcome in symptomatic cases with homoplasmy and heteroplasmy was compared. RESULTS: Heteroplasmy was detected in eight (12.9%) symptomatic and 30 (40%) asymptomatic individuals. The quantification of blood mutant mtDNA in the eight symptomatic cases ranged from 44% to 93% (mean=75%). The visual outcome of the cases with heteroplasmy was not different from that of cases with homoplasmy. There was a correlation between the proportion of mutant mtDNA and the likelihood of visual loss. CONCLUSIONS: The prevalence of heteroplasmy among pedigrees of the 11,778 LHON mutation in Thailand was similar to that of other Asian populations and may be greater than in 11,778 LHON pedigrees from white backgrounds. The proportion of mutated mtDNA correlated with visual loss, but the effect of heteroplasmy on clinical expression seemed not to relate to gender.     

Mitochondrial DNA sequence analysis in congenital myotonic dystrophy.

Mitochondrial genetic modifying factors have been suspected in several autosomally inherited diseases. The congenital variant of myotonic dystrophy, in which there is striking maternal inheritance pattern, is a likely candidate disease. To investigate this possibility, we sequenced completely the mitochondrial genome in 2 patients with congenital myotonic dystrophy. Comparison of the two sequences with control data failed to reveal a specific nucleotide variant or length variant in this disease. We conclude that a mitochondrial genetic modifying factor is not present in congenital myotonic dystrophy.     

Trephination-based,guided surgical implant placement: A clinical study

Statement of problem

Conventional guided implant surgery promises clinical success through implant placement accuracy; however, it requires multiple drills along with surgical sleeves and sleeve adapters for the horizontal and vertical control of osteotomy drills. This results in cumbersome surgery, problems with patients having limited mouth opening, and restriction to specific drill or implant manufacturers. A protocol for using trephination drills to simplify guided surgery and accommodate multiple implant systems is introduced.