Induction of lens differentiation by activation of a bZIP transcription factor, L-Maf.

After the vertebrate lens is induced from head ectoderm, lens-specific genes are expressed. Transcriptional regulation of the lens-specific alphaA-crystallin gene is controlled by an enhancer element, alphaCE2. A gene encoding an alphaCE2-binding protein, L-maf(lens-specific maf), was isolated. L-maf expression is initiated in the lens placode and is restricted to lens cells. The gene product L-Maf regulates the expression of multiple genes expressed in the lens, and ectopic expression of this transcription factor converts chick embryonic ectodermal cells and cultured cells into lens fibers. Thus, vertebrate lens induction and differentiation can be triggered by the activation of L-Maf.