homeobox genes

Homeobox genes, part of the homeobox family, contain the homeobox DNA sequence that is involved in morphogenesis.

Homeobox genes encode transcription factors, which are proteins that bind to DNA at specific promoter or enhancer or response element sequences or sites, at which they regulate transcription. As such, transcription factors are required for the recognition of specific stimulatory sequences in eukaryotic genes by RNA polymerases. Transcription factors can be selectively activated or deactivated by other proteins, often as the final step in signal transduction.

Homeobox genes were first identified in Drosophila melanogaster, and have subsequently been discovered in species from sponges to vertebrates.

Hox genes are a highly conserved subgroup of homeobox genes that are found in the Hox cluster (homeodomain, Hox complex). Hox genes function in determining the longitudinal axis of the body plan (bauplan). As regulatory genes they establish the identity of particular body regions, so Hox genes determine the location of body segments in a developing fetus or larva.

Homeotic genes in plants (MADS-box genes) are not homologous to Hox genes in animals. Since plants and animals do not share the same homeotic genes, it seems likely that homeotic genes were evolved once in the early evolution of animals and once separately in the early evolution of plants.

Mutations in homeobox genes alter gene regulation, and hence cause phenotypic changes.

Gtx is a homeodomain transcription factor. Gtx mRNA accumulates in parallel with the RNAs encoding the major structural proteins of myelin, myelin basic protein (MBP), and proteolipid protein (PLP) during postnatal brain development. Gtx is a sequence-specific DNA-binding protein, which binds DNA sequences containing a core AT-rich homeodomain binding site. [s]