Human APP cDNA harboring the Swedish double mutation (K670N,M671L) was inserted downstream of the 1.3 kb 5' flanking sequence of the mouse muscle creatine kinase Ckm, upstream of the SV40 polyadenylation signal. The 3.8 kb construct was microinjected into pronuclei of single-cell C57Bl/6 x SJL embryos. Northern blot showed relatively high expression of the transgene in skeletal muscle of line A6 mice, approximately 12 times higher than in Tg(Ckm-APP*K670N*M671L)A2Lfa mice. Western blot showed that transgenic protein expression is ~9 times higher than in mice from line A2.