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 intact (including the region containing PMP22) except for the marker representing the right arm of the YAC. Founder C1 carries 2 copies of the human transgene on chromosome 7 with an expression level half that of the endogenous mouse gene. (J:77330)