Tissue-specific expression of actin genes injected into Xenopus embryos.

We have isolated a complete Xenopus borealis cardiac actin gene, which is normally expressed in the myotomes and heart of the embryo and tadpole. After injection into the zygote, this cloned gene becomes distributed throughout the embryo, but it is expressed almost wholly in the myotomes. The same wide distribution of injected DNA but spatially restricted pattern of expression is found with a fusion between the first two actin gene exons and the last exon of a mouse beta-globin gene. By contrast, a histone-globin fusion gene is expressed fairly uniformly in all regions. We discuss the special advantages of using Xenopus in studies of tissue-specific gene expression from injected, cloned genes in early development.