Lens differentiation and crystallin regulation: a chick model

The vertebrate lens is a transparent polarized tissue that acts as the gateway for vision. The chick lens is an excellent model for studying tissue organogenesis, since it is both accessible and easily manipulated during embryonic stages. The chick lens consists of two morphologically discrete compartments, the epithelium and the fiber-cell mass. Evidence indicates that the early phases of lens development involve several sequential events, including tissue interactions, cell proliferation and differentiation. The morphological change during lens development is associated with the concurrent and distinct functions of numerous transcription factors. Diffusible molecules from the complementary neural tissue play vital roles during the entire process of lens development. Lens tissue is characterized by the ample production of crystallins, lens specific proteins which provide structural integrity and functional properties to the lens. Thus, the study of crystallin regulation should provide insight into the development of a functional lens during embryogenesis. This process has been shown to involve a complex and evolutionary conserved pathway supported by different regulatory proteins.