title: New mutations in TK2 gene associated with mitochondrial DNA depletion.
abstract: Mitochondrial deoxyribonucleic acid depletion syndromes are autosomal recessive disorders characterized by a reduction of the amount of mitochondrial deoxyribonucleic acid, which impairs the synthesis of respiratory chain complexes. Mutations in the deoxyguanosine kinase and polymerase gamma genes have been identified in hepatocerebral forms, whereas thymidine kinase 2 gene mutations have been found in patients with isolated myopathy, encephalomyopathy, or spinal muscular atrophy. Mutations in the gene encoding the beta subunit of the adenosine diphosphate-forming succinyl-coenzyme A synthetase have also been reported in a family. In this report, the clinical, molecular, morphologic, and biochemical features of five children from two independent families with an infantile encephalomyopathy are characterized. The affected children manifested muscle mitochondrial deoxyribonucleic acid depletion and three novel thymidine kinase 2 gene mutations. They consist of a homozygous substitution resulting in Ala to Val change at the highly conserved position 181 of thymidine kinase in the first family, and two heterozygous substitutions in the second family: a Cys to Trp change at residue 108 and a Leu to Pro change at residue 257 of the enzyme. Common clinical features associated with these TK2 mutations are a normal early developmental phase followed by psychomotor regression, encephalopathy often with epileptic seizures, and myopathy with features of a progressive dystrophic process.
authors.affiliation: Centro Dino Ferrari, Department of Neurological Sciences, University of Milan, I.R.C.C.S. Ospedale Maggiore Policlinico, Milano, Italy. neurogene@policlinico.mi.it
authors.forename: Sara
authors.initials: S
authors.lastname: Galbiati
authors.forename: Andreina
authors.initials: A
authors.lastname: Bordoni
authors.forename: Dimitra
authors.initials: D
authors.lastname: Papadimitriou
authors.forename: Antonio
authors.initials: A
authors.lastname: Toscano
authors.forename: Carmelo
authors.initials: C
authors.lastname: Rodolico
authors.forename: Efi
authors.initials: E
authors.lastname: Katsarou
authors.forename: Monica
authors.initials: M
authors.lastname: Sciacco
authors.forename: Anastasia
authors.initials: A
authors.lastname: Garufi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Prelle
authors.forename: M 'hammed
authors.initials: M'
authors.lastname: Aguennouz
authors.forename: Maria
authors.initials: M
authors.lastname: Bonsignore
authors.forename: Marco
authors.initials: M
authors.lastname: Crimi
authors.forename: Andrea
authors.initials: A
authors.lastname: Martinuzzi
authors.forename: Nereo
authors.initials: N
authors.lastname: Bresolin
authors.forename: Alex
authors.initials: A
authors.lastname: Papadimitriou
authors.forename: Giacomo P
authors.initials: GP
authors.lastname: Comi
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001706:Biopsy; D002648:Child; D002675:Child, Preschool; D002869:Chromosome Aberrations; D004252:DNA Mutational Analysis; D004272:DNA, Mitochondrial / Q000235:genetics*; D003937:Diagnosis, Differential; D018450:Disease Progression; D003576:Electron Transport Complex IV / Q000235:genetics; D004827:Epilepsy / Q000175:diagnosis / Q000235:genetics; D005260:Female; D005808:Genes, Recessive / Q000235:genetics*; D006580:Genetic Carrier Screening; D005838:Genotype; D006720:Homozygote; D006801:Humans; D007223:Infant; D008297:Male; D017237:Mitochondrial Encephalomyopathies / Q000175:diagnosis / Q000235:genetics*; D018482:Muscle, Skeletal / Q000473:pathology; D010641:Phenotype; D011596:Psychomotor Disorders / Q000175:diagnosis / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV; C105339:thymidine kinase 2; D013937:Thymidine Kinase