Exon 3 and 4 wwere removed by cre-mediated recombination using the B6.129S4-Meox2tm1(cre)Sor line. The protein product is predicted to include the signal sequence but lack an adjacent 123 amino acid fragment of the extracellular domain. Authors suggest that this represents a hypomorphic allele. Production of a shortened transcript was confirmed by RT-PCR using kidney tissue.