A novel monoclonal antibody identifies all avian embryonic myogenic cells and adult smooth muscle cells.

A novel monoclonal antibody, designated GIIF3, recognized prospective and differentiated smooth muscle cells in avian species studied - guinea fowl, chicken and quail. The GIIF3 antigen appeared in the myocardial, and the myotomal cells of the embryos at Hamburger-Hamilton stages 10 and 14, respectively. The expression of the GIIF3 molecule in the vascular smooth muscle cells emerged in the ventral wall of the dorsal aorta at Hamburger-Hamilton stage 16. The visceral smooth muscle cells started to produce the GIIF3 molecule from Hamburger-Hamilton stage 28 onwards. In both cardiac and skeletal muscles the GIIF3 expression gradually diminished, and it was lost by the end of the embryonic period, unlike in the differentiated vascular and visceral smooth muscle cells. In the latter cells the GIIF3 immunoreactive product showed a fine granular pattern that accumulated in the central region of the cytoplasm; it also occurred in the nucleus. A heavily stained discontinuous layer was associated with the cell membrane. The immunoblotting of the GIIF3 antibody recognized protein bands at 50 and 42 kDa in lysates of adult avian gizzard. A detailed comparative immunohistochemical study was made by smooth muscle markers, which confirmed the results of the immunoblotting, namely, that the GIIF3 monoclonal antibody recognized an avian myogenic cell specific molecule. During smooth muscle cell differentiation the GIIF3 molecule appeared as early as the alpha-smooth muscle actin, and in adult birds continued to be expressed; therefore the GIIF3 molecule could be regarded as a novel avian smooth muscle specific marker.