Transfection of ES cells with a cre construct was used to remove exon 5 along with an inserted neo cassette. Exon 5 encodes part of the catalytic RhoGEF domain. Its deletion and resulting frameshift are predicted to destroy the function of the protein and eliminate the entire C-terminus. The absence of full length and truncated protein products was confirmed by western blot on brain homogenates using either a monoclonal specific for the N-terminus or polyclonal antibody against Arhgef9.