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Title: Mitochondrial DNA replication in pre-implantation embryonic development
Author: Spikings, Emma Catherine
ISNI:       0000 0001 3475 3156
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 2007
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All eukaryotic cells possess mitochondrial DNA (mtDNA), which is maternally inherited through the oocyte, its replication being regulated by nuclear-encoded replication factors. It was hypothesised that mtDNA replication is highly regulated in oocytes, pre-implantation embryos and embryonic stem cells (ESCs) and that this may be disrupted following nuclear transfer (NT). MtDNA copy number decreased between 2-cell and 8-cell staged porcine embryos and increased between the morula and expanded blastocyst stages, coinciding with increased expression of mtDNA replication factors. Competent porcine oocytes replicated their mtDNA prior to and during in vitro maturation to produce and maintain the 100000 mtDNA copies required for fertilisation. Those oocytes in which mtDNA replication was delayed had reduced developmental ability. Expression of pluripotency-associated genes decreased as murine ESCs differentiated into embryoid bodies, although expression of mtDNA replication factors did not increase until the stage equivalent to organogenesis. Cross-species NT embryos in which the donor cell-derived mtDNA was replicated produced decreased developmental outcomes compared to those in which no mtDNA replication took place. Disruption of the strict regulation of mtDNA replication that occurs during early embryogenesis, as is likely following NT, may therefore contribute to the reduced developmental ability of embryos produced using such techniques.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RG Gynecology and obstetrics ; QP Physiology ; QH426 Genetics