Fig. 2. MtDNA copy number/cell and expression of mtDNA replication factors during spontaneous differentiation of R1 mESCs (days 1-13). (A) MtDNA was quantified using real-time PCR and normalised to the Gapdh gene. The x axis is as in B. (B) Expression of Polg, Polg2 and Tfam was quantified on undifferentiated (Und) and spontaneously differentiated R1 mESCs using RT-PCR relative quantification. Expression of each gene was compared with that of the undifferentiated R1 mESCs and 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).