title: The control of mtDNA replication during differentiation and development.
abstract: BACKGROUND
  Mitochondrial DNA (mtDNA) is important for energy production as it encodes some of the key genes of electron transfer chain, where the majority of cellular energy is generated through oxidative phosphorylation (OXPHOS). MtDNA replication is mediated by nuclear DNA-encoded proteins or enzymes, which translocate to the mitochondria, and is strictly regulated throughout development. It starts with approximately 200 copies in each primordial germ cell and these copies undergo expansion and restriction events at various stages of development.
  
  
  METHODS
  I describe the patterns of mtDNA replication at key stages of development. I explain that it is essential to regulate mtDNA copy number and to establish the mtDNA set point in order that the mature, specialised cell acquires the appropriate numbers of mtDNA copy to generate sufficient adenosine triphosphate (ATP) through OXPHOS to undertake its specialised function. I discuss how these processes are dependent on the controlled expression of the nuclear-encoded mtDNA-specific replication factors and that this can be modulated by mtDNA haplotypes. I discuss how these events are altered by certain assisted reproductive technologies, some of which have been proposed to prevent the transmission of mutant mtDNA and others to overcome infertility. Furthermore, some of these technologies are predisposed to transmitting two or more populations of mtDNA, which can be extremely harmful.
  
  
  CONCLUSIONS
  The failure to regulate mtDNA replication and mtDNA transmission during development is disadvantageous.
  
  
  CONCLUSIONS
  Manipulation of oocytes and embryos can lead to significant implications for the maternal-only transmission of mtDNA. This article is part of a Special Issue entitled Frontiers of mitochondrial research.
authors.affiliation: Mitochondrial Genetics Group, Centre for Genetic Diseases, Monash Institute of Medical Research, Monash University, 27-31 Wright Street, Clayton, Victoria 3168, Australia. Electronic address: justin.stjohn@monash.edu.
authors.forename: Justin
authors.initials: J
authors.lastname: St John
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D004261:DNA Replication / Q000502:physiology*; D004272:DNA, Mitochondrial / Q000096:biosynthesis*; D048788:Growth and Development / Q000235:genetics*; D006801:Humans; D053652:Nuclear Transfer Techniques; D011003:Ploidies
chemical_list: D004272:DNA, Mitochondrial
keywords: Assisted reproductive technology; DNA methylation; Development; Pluripotency; Replication; mtDNA