SHORTSIGHTED ACTS IN THE DECAPENTAPLEGIC PATHWAY IN DROSOPHILA EYE DEVELOPMENT AND HAS HOMOLOGY TO A MOUSE TGF-BETA-RESPONSIVE GENE

Differentiation in the Drosophila eye imaginal disc traverses the disc as a wave moving from posterior to anterior. The propagation of this wave is driven by hedgehog protein secreted by the differentiated cell s in the posterior region of the disc. Hedgehog induces decapentaplegi c expression at the front of differentiation, in the morphogenetic fur row, We have identified a gene, shortsighted, which is expressed in a hedgehog-dependent stripe in the undifferentiated cells just anterior to the furrow and which appears to be involved in the transmission of the differentiation-inducing signal; a reduction in shortsighted funct ion leads to a delay in differentiation and to a loss of photoreceptor s in the adult. shortsighted is also required for a morphogenetic move ment in the brain that reorients the second optic lobe relative to the first. shortsighted encodes a cytoplasmic leucine zipper protein with homology to a mouse gene, TSC-22, which is transcriptionally induced in response to TGF-beta.