Molecular investigations on tRNAs involved in human mitochondrial disorders.

Over the last decade, human neurodegenerative disorders which correlate with point mutations in mitochondrial tRNA genes became more and more numerous. Both the number of mutations (more than 70) and the variety of phenotypes (cardiopathies, myopathies, encephalopathies as well as diabetes, deafness or others) render the understanding of the genotype/phenotype relationships very complex. Here we first summarize the efforts undertaken to decipher the initial impact of various mutations on the structure/function relationships of tRNAs. This includes several lines of research, namely (i) investigation of human mitochrondrial tRNA structures, (ii) comparison of disease-related and polymorphic mutations at a theoretical level, and (iii) experimental investigations of affected tRNAs in the frame of mitochondrial protein synthesis. A new approach aimed at searching for long-range effects of mitochondrial tRNA mutations on a broader global mitochondrial level will also be presented. Initial results obtained by comparative mitochondrial proteomics turn out to be very promising for deciphering unexpected molecular partners involved in the pathological status of the mitochondria.