A YAC containing the human PMP22 gene with 300 kb of upstream and 100 kb of downstream sequences was used as the transgene. STS analysis using 6 markers spanning the YAC showed the integrated transgene was largely intact including the region containing PMP22. Founder C22 carries 8 copies of the human transgene on chromosome 8 with an expression pattern similar to that of the endogenous mouse gene. The expression level of each human transgene is approximately 0.4X that of one mouse gene.