Mitochondrial disorders are complex and heterogeneous diseases that may be caused by molecular defects in either the nuclear or mitochondrial genome. The biosynthesis and maintenance of the integrity of the mitochondrial genome is solely dependent on a number of nuclear proteins. Defects in these nuclear genes can lead to mitochondrial DNA (mtDNA) depletion (Spinazzola et al. Biosci Rep 27:39–51, 2007). The mitochondrial DNA (mtDNA) depletion syndromes (MDDSs) are autosomal recessive disorders characterized by a significant reduction in mtDNA content. These genes includePOLG,DGUOK,TK2,TYMP,MPV17,SUCLA2,SUCLG1,RRM2B, andC10orf2, all nine genes have mutations reported to cause various forms of MDDSs. In this chapter, we outline the real-time quantitative polymerase chain reaction (qPCR) analysis of mtDNA content in muscle or liver tissues.
