BamHI genomic fragment from coordinates +0.5 to -8 (0 is defined by an EcoRI site just upstream of the Cyp4d1 transcript) containing Cyp4d1 and the 5' half of wapl fused to cDNA sequences corresponding to the C-terminal sequences of the wapl transcript. The construct should encode the wapl 6.5kb cDNA expressed under the control of its normal promoter and upstream regulatory sequences.