A targeting vector inserted an FRT-flanked human cDNA (exons 3 through 48) into intron 2. Cre-mediated recombination removed the floxed puromycin resistance cassette inserted downstream of the human cDNA. This allele is humanized. Western blot analysis confirmed reduced protein expression in the lower limb and heart when the allele is inherited maternally. Paternal inheritance of the allele does not exhibit altered protein expression.