Abstract
Purpose: :
To explore the hypothesis that mitochondrial DNA (mtDNA) haplogroups may be relevant for clinical expression of dominant optic atrophy (DOA).
Methods: :
We defined the mtDNA haplogroups, using a PCR-based RFLP analysis protocol, in 27 DOA patients carrying different OPA 1 mutations. Clinical severity was assessed by visual acuity and evaluation of retinal nerve fiber layer thickness (RNFL thickness 3.4 acquisition protocol) with STRATUS OCT. To determine the mtDNA haplogroups effect on DOA patients phenotype, we subgrouped the patients in two clusters, depending on whether the haplogroup shift occurred from one generation to another or not. For statistical analysis, we used Pearson Χ2 test (significance was reached when P<0.05) and analysis of variance (ANOVA test, software Sigma Plot).
Results: :
A statistically significant difference (P=0.024) was observed by comparison of RNFL thickness on the temporal quadrant, the lowest mean value being found for haplogroup H, the most common in Europeans. Furthermore, a statistically significant worsening (P=0.031) of clinical features, as evaluated by visual acuity, was associated with haplogroup shift from a generation to the following.
Conclusions: :
This study provides support for the involvement of mtDNA haplogroups as modifying factor in DOA clinical expression. We found that haplogroup H was associated with a reduced RNFL thickness, as measured by OCT. Moreover, haplogroup shift between generations led to a clinical worsening, as measured by visual acuity. Further investigations on large series of patients is needed to consolidate these preliminary results.
Keywords: neuro-ophthalmology: optic nerve • gene modifiers • optic disc