Iroquois Homeobox Protein 6 (IRX6)

Members of the Iroquois complex in Drosophila, including the highly homologous homeobox genes caupolican, araucan, and mirror, act as prepattern molecules in neurogenesis.By EST database searching, Lewis et al. (1999) identified a human breast-derived partial cDNA clone containing a novel homeobox, designated IRX5. Using oligonucleotide primers designed to this clone for RACE/PCR, they obtained the full-length IRX5 cDNA as well as fragments of transcripts derived from 4 additional IRX genes, including IRX7 (which they called IRX3). The human IRX homeodomains are about 90% identical to the homeodomains of the Drosophila Iroquois complex proteins and about 93% identical to each other. Each of the IRX proteins contains a hexapeptide-like motif.