The Notch pathway mediates cell-cell interaction in many developmental proc
esses. Multiple proteins regulate the Notch pathway, among these are the pr
oducts of the fringe genes. The first fringe gene was identified in Drosoph
ila, where it is involved in the formation of the dorsal/ventral border of
the wing disc. It has now been found to be crucial for determining the dors
al/ventral border of the Drosophila eye. In vertebrates, fringe genes play
roles in the formation of the apical ectodermal ridge, the dorsal/ventral b
order in the limb bud, and in the development of semitic borders. The roles
of fringe in the neural tube or the eyes of vertebrate embryos are not cle
ar, although it is unlikely that these roles are evolutionarily related to
those in the same tissues in Drosophila. Genetic evidences suggest that Fri
nge protein functions by modulating the Notch signaling pathway, perhaps th
rough differential regulation of Notch activation by different ligands; how
ever, the mechanism underlying Fringe function remains to be investigated.