The sequence encoding a cre-mOrange fusion protein was inserted into the Ddx4 (Mvh) locus by homologous recombination with a targeting vector in ES cells. Part of exon 1 and intron 1 were replaced by the cre-mOrange sequence. A PGK-neo selection marker was inserted in the initial targeting, and was later removed by mating with FLPe-expressing mice. The mOrange fluorescent reporter in the construct does not appear to be functional.