Transgene Expression of Drosophila melanogaster Nucleoside Kinase Reverses Mitochondrial Thymidine Kinase 2 Deficiency

Shuba Krishnan,Xiaoshan Zhou,João A Paredes,Raoul V Kuiper,Sophie Curbo,Anna Karlsson

doi:10.1074/jbc.m112.437152

Shuba Krishnan, Xiaoshan Zhou + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m112.437152

Copy DOI

Abstract

A strategy to reverse the symptoms of thymidine kinase 2 (TK2) deficiency in a mouse model was investigated. The nucleoside kinase from Drosophila melanogaster (Dm-dNK) was expressed in TK2-deficient mice that have been shown to present with a severe phenotype caused by mitochondrial DNA depletion. The Dm-dNK(+/-) transgenic mice were shown to be able to rescue the TK2-deficient mice. The Dm-dNK(+/-)TK2(-/-) mice were normal as judged by growth and behavior during the observation time of 6 months. The Dm-dNK-expressing mice showed a substantial increase in thymidine-phosphorylating activity in investigated tissues. The Dm-dNK expression also resulted in highly elevated dTTP pools. The dTTP pool alterations did not cause specific mitochondrial DNA mutations or deletions when 6-month-old mice were analyzed. The mitochondrial DNA was also detected at normal levels. In conclusion, the Dm-dNK(+/-)TK2(-/-) mouse model illustrates how dTMP synthesized in the cell nucleus can compensate for loss of intramitochondrial dTMP synthesis in differentiated tissue. The data presented open new possibilities to treat the severe symptoms of TK2 deficiency.

Highlights

Thymidine kinase 2 (TK2) deficiency causes severe mitochondrial DNA depletion due to absence of nucleotides for mtDNA synthesis
The nucleoside kinase from Drosophila melanogaster (Dm-dNK) was expressed in thymidine kinase 2 (TK2)-deficient mice that have been shown to present with a severe phenotype caused by mitochondrial DNA depletion
The Dm-dNK؉/؊TK2؊/؊ mouse model illustrates how dTMP synthesized in the cell nucleus can compensate for loss of intramitochondrial dTMP synthesis in differentiated tissue

Summary

Introduction

Thymidine kinase 2 (TK2) deficiency causes severe mitochondrial DNA (mtDNA) depletion due to absence of nucleotides for mtDNA synthesis. Results: Nucleoside kinase from Drosophila melanogaster was able to rescue TK2-deficient mice. A strategy to reverse the symptoms of thymidine kinase 2 (TK2) deficiency in a mouse model was investigated. The nucleoside kinase from Drosophila melanogaster (Dm-dNK) was expressed in TK2-deficient mice that have been shown to present with a severe phenotype caused by mitochondrial DNA depletion. The Dm-dNK-expressing mice showed a substantial increase in thymidine-phosphorylating activity in investigated tissues. The dTTP pool alterations did not cause specific mitochondrial DNA mutations or deletions when 6-month-old mice were analyzed. The Dm-dNK؉/؊TK2؊/؊ mouse model illustrates how dTMP synthesized in the cell nucleus can compensate for loss of intramitochondrial dTMP synthesis in differentiated tissue. The data presented open new possibilities to treat the severe symptoms of TK2 deficiency

Objectives

Results

Conclusion