Mitochondrial DNA point mutation in human oocytes is associated with maternal age

Mitochondrial DNA (mtDNA) point mutations are known to accumulate in an age-dependent fashion in somatic tissues. This study investigated whether a point mutation (T414G) in the mtDNA control region was present in oocytes from women of advanced age. In all, 66 non-viable discarded human oocytes were analysed for the presence of a T414G transversion mutation. DNA sequence analysis confirmed the presence of this mutation in one oocyte from 11 patients between the ages of 26 and 36 years (n = 23), compared to 17 oocytes from 10 patients between the ages of 37 and 42 years (n = 43). The younger group exhibited this mtDNA point mutation in only 4.4% of oocytes compared to 39.5% from the older group (P <0.01). Therefore, single human oocytes contain the mtDNA T414G transversion point mutation that accumulates in an agedependent manner. The potential significance of this point mutation may be its association with reproductive senescence. Furthermore, since this mutation exists in the control region of the mtDNA it may affect the regulation of mtDNA transcription and replication during oocyte and post-embryonic development.