Expression of the cardiac actin gene in axolotl embryos

Axolotls are an important model system for studying heart development. Patt erning of the semitic mesoderm occurs in axolotls in a manner that is much more similar to the pattern observed in higher vertebrates than in Xenopus, For these reasons we cloned the axolotl cardiac actin gene, since this gen e is expressed during the development of both semitic and cardiac muscle in other vertebrates. In this paper we characterize its expression. Expressio n of cardiac actin RNA is switched on during gastrula stages and appears in the semitic mesoderm when it is formed; expression is later activated in t he embryonic heart. In adults the gene is expressed only in the heart. The results demonstrate that the clone encoding cardiac actin provides a useful marker for studying development of both skeletal and cardiac muscle develo pment in axolotls.