Early appearance of desmin, the muscle-type intermediate filament protein, in the rat embryo.

Antisera raised to desmin, the protein subunit of muscle-type intermediate filaments (IFs), were used to study by indirect immunofluorescence and immunoperoxidase procedures the early development of skeletal muscle in the rat embryo. The specificity of the antisera (Dahl D, Bignami A: J Histochem Cytochem 30:207, 1982) was confirmed by immune blotting on chicken gizzard extracts and purified antigen. Desmin-positive cells were first observed on day 12 by immunofluorescence and on day 13 by the immunoperoxidase procedure. Desmin immunoreactivity was not found in caudal somites in which the dermatome was present, i.e., somites where the dorso-lateral part had maintained its definite boundaries and epithelioid characteristics. Desmin-positive cells were observed within the myotome of cranial somites where the dermatome had disappeared. Compared to day 13, desmin-positive cells had extended ventrally on day 14, while on day 15, they were found in the skeletal musculature of the trunk and the limbs.