Genomic structure of the mouse Gas6 gene and the targeting vector. The 3.0-kb EcoRI-EcoRI and 3.5-kb BamHI-BamHI genomic fragments were used for the construction of the targeting vector. Homologous recombination results in the replacement of the EcoRI-BamHI genomic fragment including the translation starting codon in the Pgk-neo^r cassette, resulting in loss of Gas6 expression. DT-A, diptheria toxin A.