Figure 1

Generation of ERK5 knockout mice. A) ERK5 knockout mice were made using a targeting vector to delete exons 4 and 5 of the murine ERK5 gene through the addition of a neomycin selection cassette. A thymidine kinase cassette acts as a negative selection marker during ES cell selection. B) ES cell DNA was digested with both Hind III and Mfe I, and a Southern blot performed using a probe 3' to the targeting vector. The position of the wild type 9.5 kb fragment and targeted 3.3 kb fragment are indicated. C) DNA was isolated from E9.5 embryos and digested with Hind III and Mfe I. Southern blots were then probed with the 3' probe as described in (B)D) Soluble protein from homogenates of E9.5 embryos was run on 4–14% acrylamide gels. Immunoblotting was then carried out using antibodies which recognised ERK5, MKK5, ERK1/2 or p38.