THE BEADED INTERMEDIATE FILAMENTS AND THEIR POTENTIAL FUNCTIONS IN EYE LENS

The elongated fiber cells of the eye lens contain a unique cytoskeleta l system, the beaded chain filaments (BFs). The BFs had been morpholog ically identified more than two decades ago, but the precise identity of their subunit molecules remained unknown. Recently, use of recombin ant DNA approaches, refined morphological and immunochemical studies a nd experiments with mutant mice have allowed the molecular dissection of these structures and provided clues about their potential functions . The BFs represent a highly specialized network of intermediate filam ents (Ifs) juxtaposed to the plasma membrane. They are obligate hetero polymers composed of two lens-specific polypeptides, filensin and phak inin. In this review we discuss the properties, molecular interactions and in situ arrangement of these two proteins, and comment on their p otential roles during lens development.