HOX gene

HOX Gene

The HOX genes are a group of related genes that determine the basic structure and orientation of an organism. They are a subset of the homeobox gene family and play a crucial role in the development of the anterior-posterior axis and segment identity during embryonic development.

History

The discovery of HOX genes dates back to the 1970s when Edward B. Lewis first identified them in Drosophila melanogaster, the common fruit fly. His pioneering work on the genetic control of body segment development earned him the Nobel Prize in Physiology or Medicine in 1995.

Structure

HOX genes are characterized by a conserved DNA sequence known as the homeobox, which encodes a 60-amino acid domain called the homeodomain. This domain allows the protein to bind to specific DNA sequences, thereby regulating the expression of other genes.

Function

HOX genes are responsible for the proper placement of segment structures of various organisms during early embryonic development. They are expressed in a specific order along the anterior-posterior axis, a phenomenon known as colinearity. This ordered expression is crucial for the correct formation of body parts.

HOX Gene Clusters

In vertebrates, HOX genes are organized into clusters on different chromosomes. Humans have four HOX gene clusters: HOXA, HOXB, HOXC, and HOXD. Each cluster contains multiple HOX genes that are expressed in a specific sequence during development.

Role in Development

HOX genes are involved in the development of the central nervous system, limbs, and other body structures. They help establish the identity of different body regions by regulating the expression of downstream target genes.

Clinical Significance

Mutations in HOX genes can lead to developmental disorders and congenital malformations. For example, mutations in the HOXD13 gene are associated with synpolydactyly, a condition characterized by extra fingers or toes.

Research and Applications

HOX genes are a focus of research in developmental biology and evolutionary studies. Understanding their function and regulation can provide insights into the mechanisms of evolution and the development of complex body plans.

See Also

• Homeobox
• Gene expression
• Developmental biology

References

• Lewis, E. B. (1978). "A gene complex controlling segmentation in Drosophila." Nature.
• McGinnis, W., & Krumlauf, R. (1992). "Homeobox genes and axial patterning." Cell.