Presence of contractile proteins in mouse fetal palate prior to shelf elevation

The presence of the contractile proteins, actin and myosin, was sought in palates from day‐14.5 mouse fetuses in an effort to account for the mechanism of palate shelf elevation. Day‐14.5 tongues were carried through the same procedures as a positive control. The excised tissues were labeled with radioactive amino acids by culturing in vitro. After adding carrier actin and myosin it was possible to purify these components to constant specific activity using both palates and tongues. On this basis at least 2.1–3.3% of the radioactivity in the palates copurified with actin and about 3.6–4.7% copurified with myosin. Similarly, 1.8–3.9% and 2.5–3.3% of the radioactivity in the tongues purified with actin and myosin, respectively. About 70% of the radioactivly labeled component purified from both palates and tongues migrated with the carrier actin in SDS‐polyacrylamide gels indicating an identical molecular weight. In contrast the major radioactive component in the purified myosin from both tissues had a molecular weight (180,000) slightly lower than adult myosin. In addition it was possible to extract these proteins from the labeled palates in the form of ac to myosin. The possibility that the myosinlike component may represent an embryonic form and the role that these proteins might play in palate shelf movement is discussed.