Structure of the human PHEX transgene. Diagram of the transgene construct, which consists of a 2.4-kb rat collagen I promoter element driving a 2250-bp human PHEX coding sequence, followed by 2.2 kb of exons, introns, and polyadenylation/transcription termination sites (p/t) from the human growth hormone (hGH) gene. The growth hormone exons (boxed and numbered) are not translated. Restriction sites: B, BamHI; C, ClaI; H, XhoI; N, NotI; S, SalI; X, XbaI. The transgene was excised as a XhoI/NotI fragment and microinjected into SJL × C57BL/6 F2 oocytes