Fig. 3. The number of mtDNA copies/cell and expression of mtDNA replication factors during spontaneous differentiation of D3 mESCs (days 1-7). (A) The number of mtDNA copies/cell in undifferentiated (Und) and spontaneously differentiated D3 mESCs was determined using real-time PCR. The x axis is as in B. (B) The level of Polg, Polg2 and Tfam expression was quantified using RT-PCR relative quantification. Expression of individual genes was compared with the level of expression in undifferentiated D3 mESCs. All samples were normalised to Gapdh. Bars represent mean ± s.e.m.; significant differences between days are indicated (*P<0.05, **P<0.01, ***P<0.001).