Clinical and Molecular Features of POLG-Related Mitochondrial Disease

The inability to replicate mitochondrial genomes (mtDNA) by the mitochondrial DNA polymerase (pol gamma) leads to a subset of mitochondrial diseases. Many mutations in POLG, the gene that encodes pol gamma, have been associated with mitochondrial diseases such as myocerebrohepatopathy spectrum (MCHS) disorders, Alpers-Huttenlocher syndrome, myoclonic epilepsy myopathy sensory ataxia (MEMSA), ataxia neuropathy spectrum (ANS), and progressive external ophthalmoplegia (PEO). This chapter explores five important topics in POLG- related disease: (1) clinical symptoms that identify and distinguish POLGrelated diseases, (2) molecular characterization of defects in polymerase activity by POLG disease variants, (3) the importance of holoenzyme formation in disease presentation, (4) the role of pol gamma exonuclease activity and mutagenesis in disease and aging, and (5) novel approaches to therapy and avoidance of toxicity based on primary research in pol gamma replication.