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N. Fuhrmann, Y. Kamenisch, B. Leo-Kottler, B. Wissinger, M. V. Alavi; Identification and Characterization of a Novel 102 AA-Duplication in the GTPase Domain of Opa1. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5662.
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© ARVO (1962-2015); The Authors (2016-present)
Nowadays it is quite kerfuffle-free to differentiate autosomal dominant optic atrophy (ADOA) from Leber’s hereditary optic neuropathy (LHON) due to the different mode of inheritance and thanks to molecular genetic diagnostics. The Nosology of these two hereditary optic neuropathies goes back as far as the 1950ies when W. Jaeger put his hypothesis on the basis of the examination of a large German family.Strikingly, no mutation has been identified in this family to date.
We used Multiplex Ligation Probe Amplification (MLPA), long distance PCR and cDNA analyses to assess copy number variations in the Opa1 gene in this family. Two patients underwent full ophthalmologic examinations and agreed to skin biopsies. Therewith we investigated the consequences of this mutation on transcript and protein level, assessed mitochondrial network organization and mtDNA integrity.
Patients presented with a classical ADOA. MLPA analysis revealed a duplication of the exons 7-9 which was confirmed by long distance PCR and cDNA analysis. Segregation was verified in 53 available members of the updated pedigree and we calculate a penetrance of 88%. The mutation results in an inframe duplication of 102 AA within the GTPase domain (p.L227_K328dup102). Qualitative and quantitative Western blot analysis showed a reduction of all OPA1 isoforms when compaired to actin. In regards to other mitochondrial proteins we see an increase of Opa1 to 200%. In line we find an accumulation of the OPA1 precursor protein, but no additional bands representing protein from the mutated allele. Quantitative cDNA analysis revealed a reduction of the mutated allele whereas the overall OPA1 expression was elevated more than 2 times. Fibroblasts present with significantly fragmented mitochondrial network even when cultured under basal conditions.
More than 50 years past its first description we identified the disease causing mutation in the family that initially laid the bases for the nosology of inherited optic neuropathies. With the clinical, genetic and cell biological characterisation of this family we span nearly one century of research in optic neuropathies giving new insights into the disease mechanism of ADOA.
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