Analysis of Embryonic Chick Periderm by Monoclonal Antibody Specific against Periderm

The monoclonal antibody, 6H11, specific against embryonic chick periderm, was produced and found capable of recognizing polypeptides with 45 Kd in cytoskeletal fractions of skin and limb buds. These polypeptides were separated into two and one isoelectric variant, respectively, by two dimensional gel electrophoresis, and assigned to the acidic subfamily of cytokeratin. The ectoderm of the limb buds at stage 24 stained with 6H11. At stages 25 to 26, the experession of 6H11 in the ectoderm could no longer be detected except in a limited number of 6H11-positive cells present in the ectoderm. These positive cells were subsequently noted on the periphery of the ectoderm. They increased in number to finally form the periderm. Periderm in the dorsolateral trunk was also formed similarly by 6H11-positive cells but the timing of formation differed in the dorsal and lateral trunk. In the formation of skin integuments, such as feathers and scales, no regionality of 6H11-expression was found. The expression of 6H11 eventually decreased and ceased to be evident at about the time of hatching. Its expression in the basal epidermis during embryogenesis could not be detected. In the following, a possible mechanism of the periderm formation is discussed.