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‣ Structure of tau exon 10 splicing regulatory element RNA and destabilization by mutations of frontotemporal dementia and parkinsonism linked to chromosome 17

Varani, Luca; Hasegawa, Masato; Spillantini, Maria Grazia; Smith, Michael J.; Murrell, Jill R.; Ghetti, Bernardino; Klug, Aaron; Goedert, Michel; Varani, Gabriele
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 06/07/1999 Português
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Coding region and intronic mutations in the tau gene cause frontotemporal dementia and parkinsonism linked to chromosome 17. Intronic mutations and some missense mutations increase splicing in of exon 10, leading to an increased ratio of four-repeat to three-repeat tau isoforms. Secondary structure predictions have led to the proposal that intronic mutations and one missense mutation destabilize a putative RNA stem-loop structure located close to the splice-donor site of the intron after exon 10. We have determined the three-dimensional structure of this tau exon 10 splicing regulatory element RNA by NMR spectroscopy. We show that it forms a stable, folded stem-loop structure whose thermodynamic stability is reduced by frontotemporal dementia and parkinsonism linked to chromosome 17 mutations and increased by compensatory mutations. By exon trapping, the reduction in thermodynamic stability is correlated with increased splicing in of exon 10.

‣ Functional analyses of troponin T mutations that cause hypertrophic cardiomyopathy: Insights into disease pathogenesis and troponin function

Sweeney, H. Lee; Feng, Huisheng S.; Yang, Zhaouhui; Watkins, Hugh
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 24/11/1998 Português
Relevância na Pesquisa
37.619502%
Mutations in a number of cardiac sarcomeric protein genes cause hypertrophic cardiomyopathy (HCM). Previous findings indicate that HCM-causing mutations associated with a truncated cardiac troponin T (TnT) and missense mutations in the β-myosin heavy chain share abnormalities in common, acting as dominant negative alleles that impair contractile performance. In contrast, Lin et al. [Lin, D., Bobkova, A., Homsher, E. & Tobacman, L. S. (1996) J. Clin. Invest. 97, 2842–2848] characterized a TnT point mutation (Ile79Asn) and concluded that it might lead to hypercontractility and, thus, potentially a different mechanism for HCM pathogenesis. In this study, three HCM-causing cardiac TnT mutations (Ile79Asn, Arg92Gln, and ΔGlu160) were studied in a myotube expression system. Functional studies of wild-type and mutant transfected myotubes revealed that all three mutants decreased the calcium sensitivity of force production and that the two missense mutations (Ile79Asn and Arg92Gln) increased the unloaded shortening velocity nearly 2-fold. The data demonstrate that TnT can alter the rate of myosin cross-bridge detachment, and thus the troponin complex plays a greater role in modulating muscle contractile performance than was recognized previously. Furthermore...