TISSUE-SPECIFIC EXPRESSION OF AN ALPHA-SKELETAL ACTIN LACZ FUSION GENE DURING DEVELOPMENT IN TRANSGENIC MICE

Transgenic mice carrying a chimaeric transgene containing 730 bp of th e 5'-flanking sequences and the entire first intron of the rat alpha-s keletal actin gene fused to the lacZ reporter gene have been produced by microinjection. The lacZ reporter gene was used to verify the suita bility of using the rat alpha-actin promoter elements to target expres sion of genes of agricultural and therapeutic value exclusively to ske letal and heart muscle cells and fibres of transgenic mice. Expression of the transgene indicates a tightly regulated developmental and musc le specific control of the rat alpha-skeletal actin gene, making it a useful promoter for gene targeting to muscle tissues. The cells destin ed to form muscle tissues in these transgenic mice are readily visuali zed in intact embryos by staining for beta-galactosidase activity, mak ing them a suitable animal model for studying the origin and developme nt of skeletal and cardiac muscle tissues.