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 low expression of the transgene in skeletal muscle of line A2 mice.