A concerted action of a paired-type homeobox gene, aristaless, and a homolog of Hox11/tlx homeobox gene, clawless, is essential for the distal tip development of the Drosophila leg.

Abstract The subdivision of the developing field by region-specific expression of genes encoding transcription factors is an essential step during appendage development in arthropod and vertebrates. In Drosophila leg development, the distal-most region (pretarsus) is specified by the expression of homeobox genes, aristaless and Lim1 , and its immediate neighbor (distal tarsus) is specified by the expression of a pair of Bar homeobox genes. Here, we show that one additional gene, clawless , which is a homolog of vertebrate Hox11/tlx homeobox gene family and formerly known as C15 , is specifically expressed in the pretarsus and cooperatively acts with aristaless to repress Bar and possibly to activate Lim1 . Similar to aristaless , the maximal expression of clawless requires Lim1 and its co-factor, Chip. Bar attenuates aristaless and clawless expression through Lim1 repression. Aristaless and Clawless proteins form a complex capable of binding to specific DNA targets, which cannot be well recognized solely by Aristaless or Clawless.