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Leber’s hereditary optic neuropathy (LHON) and Autosomal Dominant Optic Atrophy (ADOA) are the two most common inherited optic neuropathies and both are the result of mitochondrial dysfunctions. Despite the primary mutations causing these disorders are different, being an mtDNA mutation in subunits of complex I in LHON and defects in the nuclear gene encoding the mitochondrial protein OPA1 in ADOA, both pathologies share some peculiar features, such a variable penetrance and tissue-specificity of the pathological processes. Probably, one of the most interesting and unclear aspect of LHON is the variable penetrance. This phenomenon is common in LHON families, most of them being homoplasmic mutant. Inter-family variability of penetrance may be caused by nuclear or mitochondrial ‘secondary’ genetic determinants or other predisposing triggering factors. We identified a compensatory mechanism in LHON patients, able to distinguish affected individuals from unaffected mutation carriers. In fact, carrier individuals resulted more efficient than affected subjects in increasing the mitochondrial biogenesis to compensate for the energetic defect. Thus, the activation of the mitochondrial biogenesis may be a crucial factor in modulating penetrance, determining the fate of subjects harbouring LHON mutations. Furthermore, mtDNA content can be used as a molecular biomarker which, for the first time, clearly differentiates LHON affected from LHON carrier individuals, providing a valid mechanism that may be exploited for development of therapeutic strategies. Although the mitochondrial biogenesis gained a relevant role in LHON pathogenesis, we failed to identify a genetic modifying factor for the variable penetrance in a set of candidate genes involved in the regulation of this process. A more systematic high-throughput approach will be necessary to select the genetic variants responsible for the different efficiency in activating mitochondrial biogenesis. A genetic modifying factor was instead identified in the MnSOD gene. The SNP Ala16Val in this gene seems to modulate LHON penetrance, since the Ala allele in this position significantly predisposes to be affected. Thus, we propose that high MnSOD activity in mitochondria of LHON subjects may produce an overload of H2O2 for the antioxidant machinery, leading to release from mitochondria of this radical and promoting a severe cell damage and death ADOA is due to mutation in the OPA1 gene in the large majority of cases. The causative nuclear defects in the remaining families with DOA have not been identified yet, but a small number of families have been mapped to other chromosomal loci (OPA3, OPA4, OPA5, OPA7, OPA8). Recently, a form of DOA and premature cataract (ADOAC) has been associated to pathogenic mutations of the OPA3 gene, encoding a mitochondrial protein. In the last year OPA3 has been investigated by two different groups, but a clear function for this protein and the pathogenic mechanism leading to ADOAC are still unclear. Our study on OPA3 provides new information about the pattern of expression of the two isoforms OPA3V1 and OPA3V2, and, moreover, suggests that OPA3 may have a different function in mitochondria from OPA1, the major site for ADOA mutations. In fact, based on our results, we propose that OPA3 is not involved in the mitochondrial fusion process, but, on the contrary, it may regulate mitochondrial fission. Furthermore, at difference from OPA1, we excluded a role for OPA3 in mtDNA maintenance and we failed to identify a direct interaction between OPA3 and OPA1. Considering the results from overexpression and silencing of OPA3, we can conclude that the overexpression has more drastic consequences on the cells than silencing, suggesting that OPA3 may cause optic atrophy via a gain-of-function mechanism. These data provide a new starting point for future investigations aimed at identifying the exact function of OPA3 and the pathogenic mechanism causing ADOAC.

Orientador : Bernardo Beiguelman / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-07-18T00:58:31Z (GMT). No. of bitstreams: 1 Arena_JoseFernandoPereira_D.pdf: 7439917 bytes, checksum: d98537ff823f4f5a1c24035e14bae80d (MD5) Previous issue date: 1974 / Resumo: Não informado / Abstract: Not informed / Doutorado / Genetica Medica / Doutor em Ciências Médicas

Orientador: Danilo Moretti-Ferreira / Banca: Claudia Aparecida Rainho / Banca: Ligia Maria Suppo Souza Rúgulo / Banca: Célia Maria Giacheti / Banca: Ester Silveira Ramos / Resumo: A síndrome de Williams-Beuren (SWB) é uma afecção genética rara, com frequência estimada em 1:7500 nascidos vivos, caracterizada por alterações do desenvolvimento associados a deficiência mental moderada, anomalias cardíacas e fácies peculiar, além de um comportamento amigável, alegre e desinibido. O diagnóstico clínico é bastante acurado, porém as diferenças fenotípicas conforme a idade pode dificultar o diagnóstico. O diagnóstico clínico pode ser confirmado pelo diagnóstico molecular, sendo a técnica de FISH, o padrão ouro deste diagnóstico. A SWB tem por etiologia a deleção em 7q11.23, sendo esta ocorrência esporádica. A deleção típica envolve uma região cromossômica de 1.5 Mb ou 1.8 Mb contendo 28 genes denominada de região crítica da SWB. O mecanismo de deleção está ligado as duplicações segmentarias (DSs) ou repetições com baixo números de cópias LCRs. A origem da deleção tem sido atribuída ao rearranjo desigual na meiose devido as recombinações homologas não alélicas (Nonallelic homologous recombination-NAHRs), que pode ocorrer entre regiões repetidas de baixo número de cópias (LCRs). Para termos a indicação ou não da realização do exame de FISH, existem na literatura 3 sistemas de pontuações (escores), publicados por Lowery et al,1997, AAP, 2001 e Sugayama et al, 2007. O presente estudo teve como um dos seus objetivos a verificação da especificidade e da sensibilidade dentre os 3 sistemas publicados, para termos a indicação de qual seria o melhor a ser aplicado. Para tanto foram utilizados um banco de características clínicas com 250 pacientes que já haviam realizados exames da FISH e onde foram aplicados os 3 sistemas de escores. Todos os três sistemas de escores apresentaram alta sensibilidade e baixa especificidade, porém o escore descrito por Lowery et al., 1995 foi ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Williams - Beuren syndrome (WBS ) is a rare genetic disorder , often estimated at 1:7500 live births , characterized by developmental disorders associated with moderate mental retardation , cardiac anomalies and peculiar facies , and a friendly demeanor , cheerful and uninhibited . The clinical diagnosis is fairly accurate, but the phenotypic differences according to age can make diagnosis difficult. The clinical diagnosis can be confirmed by molecular diagnosis, and the technique of FISH, the gold standard for this diagnosis . The SWB is etiology deletion in 7q11.23, which is sporadic. The typical deletion involves a chromosomal region of 1.5 Mb or 1.8 Mb containing 28 genes designated critical region of SWB. The mechanism of deletion is linked to segmental duplications (SDs) or repetitions with low copy numbers of LCRs. The origin of the deletion has been attributed to unequal rearrangement in meiosis because nonallelic homologous recombination (NAHRs), which can occur from repeated regions of low copy number (LCRs). To get an indication whether or not the examination of FISH, in literature there are 3 systems scores (scores), published by Lowery et al, 1997, AAP, 2001 and Sugayama et al, 2007. The present study had as one of its objectives to verify the specificity and sensitivity among 3 systems publish, to terms to indicate what would best be applied. Therefore, we used a database of clinical characteristics of 250 patients who had already performed the FISH tests were applied and where the three scoring systems. All the three scoring systems showed high sensitivity and low specificity, but the score described powder Lowery et al., 1995 was considered the easiest application. The second objective of this study was to evaluate the sizes of the fragments deleted in order to infer the local break points. Thus were studied for the first time in the literature,...(Complete abstract click electronic access below) / Doutor