Solving a 50 year mystery of a missing OPA1 mutation: more insights from the first family diagnosed with autosomal dominant optic atrophy

Background: Up to the 1950s, there was an ongoing debate about the diversity of hereditary optic neuropathies, in particular as to whether all inherited optic atrophies can be ascribed to Leber's hereditary optic neuropathy (LHON) or represent different disease entities. In 1954 W. Jaeger published a detailed clinical and genealogical investigation of a large family with explicit autosomal dominant segregation of optic atrophy thus proving the existence of a discrete disease different from LHON, which is nowadays known as autosomal dominant optic atrophy (ADOA). Since the year 2000 ADOA is associated with genomic mutations in the OPA1 gene, which codes for a protein that is imported into mitochondria where it is required for mitochondrial fusion. Interestingly enough, the underlying mutation in this family has not been identified since then. Results: We have reinvestigated this family with the aim to identify the mutation and to further clarify the underlying pathomechanism. Patients showed a classical non-syndromic ADOA. The long term deterioration in vision in the two teenagers examined 50 years later is of particular note 5/20 to 6/120. Multiplex ligation probe amplification revealed a duplication of the OPA1 exons 7-9 which was confirmed by long distance PCR and cDNA analysis, resulting in an in-frame duplication of 102 amino acids. Segregation was verified in 53 available members of the updated pedigree and a penetrance of 88% was calculated. Fibroblast cultures from skin biopsies were established to assess the mitochondrial network integrity and to qualitatively and quantitatively study the consequences of the mutation on transcript and protein level. Fibroblast cultures demonstrated a fragmented mitochondrial network. Processing of the OPA1 protein was altered. There was no correlation of the OPA1 transcript levels and the OPA1 protein levels in the fibroblasts. Intriguingly an overall decrease of mitochondrial proteins was observed in patients' fibroblasts, while the OPA1 transcript levels were elevated. Conclusions: The thorough study of this family provides a detailed clinical picture accompanied by a molecular investigation of patients' fibroblasts. Our data show a classic OPA1-associated non-syndromic ADOA segregating in this family. Cell biological findings suggest that OPA1 is regulated by post-translational mechanisms and we would like to hypothesize that loss of OPA1 function might lead to impaired mitochondrial quality control. With the clinical, genetic and cell biological characterisation of a family described already more than 50 years ago, we span more than half a century of research in optic neuropathies

Improved Spectral Purity of 222‐nm Irradiation Eliminates Detectable Cyclobutylpyrimidine Dimers Formation in Skin Reconstructs even at High and Repetitive Disinfecting Doses

UVC222 nm has germicidal effects with potential clinical applications. However, UVC irradiation is capable of inducing DNA damage like cyclobutylpyrimidine dimers (CPD). Although new devices have emission peaks in the short-wavelength region of UVC (~222 nm), the remaining “collateral” radiation at longer wavelengths could be harmful to human health. We investigated the DNA damage caused by far-UVC 222 nm KrCl exciplex radiation on human skin reconstructs after additional filtering using silica filters. The skin reconstructs were irradiated with 100 mJ cm−2, 500 mJ cm−2, and 3 × 500 mJ cm−2 unfiltered and filtered (230–270 nm suppressed) far-UVC or UVB (308 nm) radiation. UVB and non-filtered UVC irradiation induced a significant amount of CPDs, compared with the background. Filtered far-UVC lowered the CPD amount compared with unfiltered UVC and UVB treatments. Repetitive UVC irradiation did not result in the accumulation of CPDs compared with UVB treatment. Reduction in excess of 99.9% of E. coli, S. aureus and C. albicans was detected after applying far-UVC radiation. This identifies a therapeutic window in which microorganisms are killed but tissue is still alive and not damaged, which could give rise to new clinical applications

Proteins of nucleotide and base excision repair pathways interact in mitochondria to protect from loss of subcutaneous fat, a hallmark of aging

Defects in the DNA repair mechanism nucleotide excision repair (NER) may lead to tumors in xeroderma pigmentosum (XP) or to premature aging with loss of subcutaneous fat in Cockayne syndrome (CS). Mutations of mitochondrial (mt)DNA play a role in aging, but a link between the NER-associated CS proteins and base excision repair (BER)-associated proteins in mitochondrial aging remains enigmatic. We show functional increase of CSA and CSB inside mt and complex formation with mtDNA, mt human 8-oxoguanine glycosylase (mtOGG)-1, and mt single-stranded DNA binding protein (mtSSBP)-1 upon oxidative stress. MtDNA mutations are highly increased in cells from CS patients and in subcutaneous fat of aged Csbm/m and Csa−/− mice. Thus, the NER-proteins CSA and CSB localize to mt and directly interact with BER-associated human mitochondrial 8-oxoguanine glycosylase-1 to protect from aging- and stress-induced mtDNA mutations and apoptosis-mediated loss of subcutaneous fat, a hallmark of aging found in animal models, human progeroid syndromes like CS and in normal human aging

Progeroid Syndromes and UV-Induced Oxidative DNA Damage

Progeroid syndromes are a group of diseases characterized by signs of premature aging. These syndromes comprise diseases such as Werner syndrome, Bloom syndrome, Rothmund–Thomson syndrome, Hutchinson–Gilford syndrome, Fanconi anemia, and ataxia–telangiectasia, as well as xeroderma pigmentosum, trichothiodystrophy, and Cockayne syndrome. Clinical symptoms of premature aging are skin atrophy with loss of cutaneous elasticity, dysfunction of cutaneous appendices, degeneration of the central nervous system and an increased susceptibility for malignant tumors. Genetic defects in the repair of DNA damage can lead to progeroid syndromes, and it is becoming increasingly evident that direct DNA damage and indirect damage by highly reactive oxygen species play central roles in aging. The clinical signs of progeroid syndromes and the molecular aspects of UV (ultraviolet radiation)-induced oxidative stress in aging are discussed

Cockayne syndrome

Zusammenfassung Das Cockayne-Syndrom (CS) ist eine seltene, autosomal-rezessive Erkrankung, charakterisiert durch vorzeitige Alterungssymptomatik mit Degeneration des zentralen Nervensystems, Verlust des subkutanen Fettgewebes und Kachexie. Auslöser dieser Erkrankung sind autosomal-rezessiv vererbte Mutationen im CSA- und CSB-Gen. Im Zellkern sind das CSA- und das CSB-Protein sowohl an der DNA-Reparatur als auch der Transkription beteiligt. Außerhalb des Zellkerns schützen die CS-Proteine im Mitochondrium vor oxidativ induzierten mitochondrialen (mt) DNA-Schäden und spielen somit möglicherweise eine wichtige Rolle beim altersbedingten Verlust des subkutanen Fettgewebes. Damit ist das CS nicht nur wichtig als Modellerkrankung zur Untersuchung molekularer Mechanismen der DNA-Reparatur, sondern auch für das Verständnis der Ursachen des Alterungsprozesses.</jats:p

Distinct profile of the mitochondrial DNA common deletion in benign skin lesions

Mutations of mitochondrial (mt) DNA, particularly the 4977 bp long common deletion, are increased in aging tissues and preferentially found in chronologically and photoaged skin. Mutations of human mitochondrial DNA (mtDNA) have also been identified in malignant tumors of the skin and of other organs. However, benign skin lesions have not yet been investigated. We analyzed the frequency of the common deletion in 27 benign skin lesions [8 seborrheic keratoses (SK), 5 epidermal nevi (EN), 14 solar lentigos (SL)] by quantitative real-time PCR, because SK and especially SL have been related to (photo)aged skin. All SK and four of five EN displayed reduced common deletion levels compared with adjacent normal skin. In contrast, 50% of SL revealed a higher percentage of the common deletion than the adjacent normal skin, and some SL showed very high absolute common deletion levels up to 14% of total mtDNA. Our results show that the amount of the common deletion is significantly different in benign skin lesions and raise further questions regarding the pathogenesis of SL and its possible role as a precursor lesion of SK