Infantile encephalopathy and defective mitochondrial DNA translation in patients with mutations of mitochondrial elongation factors EFG1 and EFTu.
Mitochondrial protein translation is a complex process performed within mitochondria by an apparatus composed of mitochondrial DNA (mtDNA)-encoded RNAs and nuclear DNA-encoded proteins. Although the latter by far outnumber the former, the vast majority of mitochondrial translation defects in humans have been associated with mutations in RNA-encoding mtDNA genes, whereas mutations in protein-encoding nuclear genes have been identified in a handful of cases. Genetic investigation involving patients with defective mitochondrial translation led us to the discovery of novel mutations in the mitochondrial elongation factor G1 (EFG1) in one affected baby and, for the first time, in the mitochondrial elongation factor Tu (EFTu) in another one. Both patients were affected by severe lactic acidosis and rapidly progressive, fatal encephalopathy. The EFG1-mutant patient had early-onset Leigh syndrome, whereas the EFTu-mutant patient had severe infantile macrocystic leukodystrophy with micropolygyria. Structural modeling enabled us to make predictions about the effects of the mutations at the molecular level. Yeast and mammalian cell systems proved the pathogenic role of the mutant alleles by functional complementation in vivo. Nuclear-gene abnormalities causing mitochondrial translation defects represent a new, potentially broad field of mitochondrial medicine. Investigation of these defects is important to expand the molecular characterization of mitochondrial disorders and also may contribute to the elucidation of the complex control mechanisms, which regulate this fundamental pathway of mtDNA homeostasis.
Valente
Lucia
L
Pierfranco and Luisa Mariani Center for Research on Children's Mitochondrial Disorders, Division of Molecular Neurogenetics, National Neurological Institute "Carlo Besta," Milano, Italy.
Tiranti
Valeria
V
Marsano
Rene Massimiliano
RM
Malfatti
Edoardo
E
Fernandez-Vizarra
Erika
E
Donnini
Claudia
C
Mereghetti
Paolo
P
De Gioia
Luca
L
Burlina
Alberto
A
Castellan
Claudio
C
Comi
Giacomo P
GP
Savasta
Salvatore
S
Ferrero
Iliana
I
Zeviani
Massimo
M
D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000096:biosynthesis / Q000235:genetics*; D001921:Brain / Q000002:abnormalities; D002478:Cells, Cultured; D002675:Child, Preschool; D004272:DNA, Mitochondrial / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D017237:Mitochondrial Encephalomyopathies / Q000151:congenital / Q000235:genetics / Q000473:pathology*; D024101:Mitochondrial Proteins / Q000096:biosynthesis / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020653:Peptide Elongation Factor G / Q000096:biosynthesis / Q000235:genetics*; D010444:Peptide Elongation Factor Tu / Q000096:biosynthesis / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
D000951:Antigens, Neoplasm; D004272:DNA, Mitochondrial; C441680:GFM1 protein, human; D024101:Mitochondrial Proteins; D020653:Peptide Elongation Factor G; C091648:TUFM protein, human; D010444:Peptide Elongation Factor Tu