Fig. 7. Diminished expression of Cdc7 in Cdc7^–/–tg MEFs and testes. The levels of Cdc7 protein in MEFs [(A), left], ES cells [(A), right] and testes (B) were determined by western blot analysis. Cdc7^–/–tg MEFs express Cdc7 protein at levels five times lower than that in wild-type MEFs, whereas the level of Cdc7 in Cdc7^–/–tg ES cells is ∼3- to 5-fold higher than that of the wild-type ES cells. The Cdc7 protein level in Cdc7^–/–tg testes is 10 times lower than those in the wild-type and Cdc7^+/–tg testes. α-tubulin is shown as a loading control. L and S denote two alternative spliced forms of murine Cdc7 protein, which are identical in functions. The transgene encodes the form S.