The Iroquois family of genes: from body building to neural patterning

The Iroquois (Iro) family of genes are found in nematodes, insects and vert ebrates. They usually occur in one or two genomic clusters of three genes e ach and encode transcriptional controllers that posses a characteristic hom eodomain. The Iro genes function early in development to specify the identi ty of diverse territories of the body, such as the dorsal head and dorsal m esothorax of Drosophila and the neural plate of Xenopus. In some aspects th ey act in the same way as classical selector genes, but they display specif ic properties that place them into a category of their own. Later in develo pment in both Drosophila and vertebrates, the Iro genes function again to s ubdivide those territories into smaller domains.