The expression of melanosomal matrix protein in the transdifferentiation of pigmented epithelial cells into lens cells.

A monoclonal antibody (MC/1) was constructed against melanosomes purified from the chicken pigmented epithelial cells (PECs) in order to characterize the differentiative phenotypes of PEC in the process of transdifferentiation into lens cells. Immunofluorescent studies revealed that MC/1 antibody specifically stains both retinal PECs in the eye and melanocytes in the skin, of chicken embryos. Immunoelectron microscopy showed that the antigen molecules are located on the peripheral region of the melanosomal matrix. A single protein band with an apparent molecular weight of 115,000 was labelled by MC/1 in Western blotting. The 115 kDa polypeptide identified by MC/1 is considered to be a member of the melanosomal matrix proteins. The maintenance of specificity of pigment cell nature is followed in the system of transdifferentiation of PEC into lens in vitro, utilizing 115 kDa protein as a marker. In the dedifferentiated PECs, this protein was undetectable.