（C）Equarin

　Lens is an important source of signals that influence the eye development and a variety of genes expressed by the lens have been identified. FGF signaling has been implicated in lens induction, lens cell proliferation, and lens fiber differentiation. However, the identification of additional molecule(s) mediating signal transductions will extend our knowledge of the molecular mechanisms of lens development. We performed the signal sequence trap screens and found a novel molecule expressed in the lens equatorial region, and therefore designated ‘Equarin’.

　During eye development, Equarin is first detected in the lens placode. As lens development proceeds, Equarin is expressed in the lens equatorial region with a high-dorsal-to-low-ventral gradient. Gain-of-function and loss-of-function assays provide evidence that Equarin serves as a bona fide differentiation factor during lens development. Further, we showed that Equarin promoted lens cell adhesion in a dose-dependent manner through heparan sulfate proteoglycan of syndecan-3. In this symposium, we will introduce the soluble molecule, Equarin, and discuss its vital role in multiple aspects of lens development.