Thymidine kinase 2 (H126N) knockin mice show the essential role of balanced deoxynucleotide pools for mitochondrial DNA maintenance.
Mitochondrial DNA (mtDNA) depletion syndrome (MDS), an autosomal recessive condition, is characterized by variable organ involvement with decreased mtDNA copy number and activities of respiratory chain enzymes in affected tissues. MtDNA depletion has been associated with mutations in nine autosomal genes, including thymidine kinase (TK2), which encodes a ubiquitous mitochondrial protein. To study the pathogenesis of TK2-deficiency, we generated mice harboring an H126N Tk2 mutation. Homozygous Tk2 mutant (Tk2(-/-)) mice developed rapidly progressive weakness after age 10 days and died between ages 2 and 3 weeks. Tk2(-/-) animals showed Tk2 deficiency, unbalanced dNTP pools, mtDNA depletion and defects of respiratory chain enzymes containing mtDNA-encoded subunits that were most prominent in the central nervous system. Histopathology revealed an encephalomyelopathy with prominent vacuolar changes in the anterior horn of the spinal cord. The H126N TK2 mouse is the first knock-in animal model of human MDS and demonstrates that the severity of TK2 deficiency in tissues may determine the organ-specific phenotype.
Akman
Hasan O
HO
Department of Neurology, Columbia University Medical Center, New York, NY 10032, USA.
Dorado
Beatriz
B
López
Luis C
LC
García-Cazorla
Angeles
A
Vilà
Maya R
MR
Tanabe
Lauren M
LM
Dauer
William T
WT
Bonilla
Eduardo
E
Tanji
Kurenai
K
Hirano
Michio
M
D000818:Animals; D003854:Deoxyribonucleotides / Q000235:genetics / Q000378:metabolism*; D042967:Electron Transport Complex I / Q000235:genetics / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D028361:Mitochondrial Diseases / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D016254:Mutagenesis, Insertional; D020125:Mutation, Missense; D009928:Organ Specificity; D013937:Thymidine Kinase / Q000172:deficiency* / Q000235:genetics
D003854:Deoxyribonucleotides; D003576:Electron Transport Complex IV; C105339:thymidine kinase 2; D013937:Thymidine Kinase; D042967:Electron Transport Complex I