Hox Transcription Factors: Modulators of Cell-Cell and Cell-Extracellular Matrix Adhesion

Figure 1

Arrangement of Hox genes in the Drosophila and mammalian genomes. In Drosophila, eight Hox genes clustered on a single chromosome, the homeotic complex (HOM-C), are divided into two groups: the Antennapedia complex (ANT-C) and Bithorax complex (BX-C). ANT-C comprises five Hox genes: labial   (lab), proboscipedia (pb), Deformed (Dfd), Sex combs reduced (Scr), and Antennapedia (Antp). The BX-C consists of three Hox genes: Ultrabithorax (Ubx), Abdominal-A (Abd-A), and Abdominal-B (Abd-B). In mammals, 39 Hox genes are divided into four separate clusters (HoxA, HoxB, HoxC, and HoxD) on four different chromosomes. In each cluster, Hox genes are tandem arranged in sequence from 3′ to 5′. Hox genes with the same number are referred to as paralogs. In the embryo, expression of the 3′ paralogs occurs earlier and more anteriorly along the anterior-posterior axis, whereas the 5′ paralogs are expressed later and more posteriorly.