MTDNA HAPLOTYPE ANALYSIS IN FINNISH FAMILIES WITH LEBER HEREDITARY OPTIC NEURORETINOPATHY

The mitochondrial DNA (mtDNA) sequence variation of 24 Finnish Leber h ereditary optic neuroretinopathy (LHON) probands was characterized by sequencing and restriction endonuclease analyses. All LHON-associated substitutions and Caucasoid haplogroup-specific mutations were screene d in the families. Analysis of the mtDNAs revealed that the Finnish LH ON families have two unique features: an absence of the ND6/14484 muta tion and a high number of families (10/24) without the primary mutatio ns ND1/3460 and ND4/11778. Furthermore, the LHON families showed consi derable mtDNA heterogeneity: among 24 families 22 haplotypes were dete cted. Overall, the haplogrouping of LHON families was similar to other European populations. However, the frequency of ND4/11778-positive fa milies in haplogroup J was high, which may indicate that background mu tations in this haplogroup together with the ND4/11778 primary mutatio n promote the penetrance of LHON.