ABSTRACT
The purpose of this experiment was to analyse location and time of appearance of lens proteins during lens development.
Applying the agar-diffusion technique of Ouchterlony the adult lens was found to contain substantial amounts of at least seven soluble antigenic substances, grouped into three main fractions and referred to as Fractions I, II, and III. While Fraction I consists of one antigenic substance, Fraction II contains at least four components and Fraction III usually two components.
Fraction I appears to be identical to the protein alpha crystallin (m.w. approximately 1,000,000) as prepared by continuous-flow electrophoresis and tested on homogeneity and identity by ultracentrifugation and paper electrophoresis. It is detected in the epithelial cells of the lens placode before the appearance of any other lens antigens and is thus considered to be the first lens protein to arise during organogenesis. The importance of this protein for lens development is also shown by its presence in the lens of representative species of the vertebrate series and by its presence in iris, retina, and cornea—that is, those tissues which show the capacity to form a lens after removal of the original lens.
Fraction II appears to be identical to beta crystallin (m.w. approximately 200,000) and is characterized by at least four closely related antigenic subfractions, which appear at the onset of differentiation and growth of the nuclear lens fibres. As it is localized in the nucleus of the lens, the typical site of con genital cataracts, it is believed to be the main target for teratogenic factors such as German measles virus, which causes a cataract only if acting during differentiation and growth of the nuclear lens fibres.
Fraction III appears to be identical to gamma crystallin (m.w. approximately 60,000) and is the last lens antigen to arise during lens development. Its morphological position could not be determined.