A human insulin receptor cDNA was inserted in exon 3 of a 3kbp human TTR fragment containin the promoter and exons 1-3. The insulin receptor cDNA is thus placed under the control of the human TTR promoter. Three founder lines were established (L1, L2, L3). Highest expression was found in L1. Expression in L3 which has a copy number of 1 was 29% of expression in L1.