text: The muscle-related genes included actin, tropomyosin, troponin I, myosin regulatory light chain, myosin light chain kinase, myosin heavy chain, calmodulin, calponin, calcium vector protein, creatine kinase, muscle LIM protein, and SH3-binding glutamate-rich protein, suggesting that vertebrate skeletal and smooth muscle-type genes are simultaneously expressed in the amphioxus notochord.