Immunofluorescent detection of actin in non-muscle cells of the developing mouse palatal shelf

Cryostat sections of foetal mouse heads, taken at 14–15 days in utero, were incubated first in serum containing smooth muscle auto-antibody and then in fluorescein-conjugated rabbit or goat IgG directed against human IgG. A positive fluorescent reaction was observed in epithelial and mesenchymal cells of the secondary palate, oral mucosa, nasal septum and tongue. Incubating the auto-antibody-containing serum with highly purified actin blocked the auto-antibody and produced no reaction, suggesting that the contractile protein detected in non-muscle cells of the developing palatal shelf contain the muscle protein, actin.