Human Molecular Genetics Advance Access published online on May 8, 2008
Human Molecular Genetics, doi:10.1093/hmg/ddn143
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Thymidine kinase 2 (H126N) knockin mice show the essential role of balanced deoxynucleotide pools for mitochondrial DNA maintenance
1 Department of Neurology, Columbia University Medical Center, New York, NY, USA 2 Department of Neurology, Hospital Sant Joan de Deu, and CIBER-ER, Instituto de Salud Carlos III, Barcelona, Spain 3 Centre d'Investigacions en Bioquímica i Biología Molecular (CIBBIM), Hospital Universitari Vall d'Hebron, Barcelona, Spain 4 Department of Pharmacology, Columbia University Medical Center, New York, NY, USA 5 Department of Pathology, Columbia University Medical Center, New York, NY, USA
* To whom correspondence should be addressed: Michio Hirano, MD, Columbia University Medical Centerm, 1150 St. Nicholas Ave., Russ Berrie Medical Pavilion, Room 317, New York, NY 10032, Tel: 212-305-1048, Fax: 212-305-3986, e-mail: mh29{at}columbia.edu
Received April 9, 2008; Revised May 6, 2008; Accepted May 6, 2008
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 2-3 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.
These authors contributed equally to this work.
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