Homeobox genes

Homeobox genes are a group of related genes that control the body plan of an embryo along the head-tail axis. This group of genes was first discovered in fruit flies, where mutations in these genes led to dramatic changes in body structure. Homeobox genes have since been identified in many other species, including humans, and they play a crucial role in the development of many organs and tissues.

History

The concept of the homeobox gene was first introduced in the 1980s following studies on the fruit fly Drosophila melanogaster. Researchers Edward B. Lewis, Christiane Nüsslein-Volhard and Eric F. Wieschaus discovered that a specific set of genes, which they named homeotic genes, were responsible for the body plan of the fruit fly. These genes were later found to contain a common sequence of DNA, which was named the homeobox. For their work, Lewis, Nüsslein-Volhard and Wieschaus were awarded the Nobel Prize in Physiology or Medicine in 1995.

Function

Homeobox genes encode homeodomain proteins, which are transcription factors that bind to specific DNA sequences and regulate the activity of other genes. This means that homeobox genes act as master control genes that determine the identity of body parts. For example, they can turn on genes that lead to the development of arms, legs, and other body parts at specific locations in the embryo.

Classification

Homeobox genes are classified into several families based on the sequence and function of their homeodomains. These families include the HOX genes, which are involved in the formation of the body axis, and the PAX genes, which play a role in the development of the nervous system and sensory organs.

Medical significance

Mutations in homeobox genes can lead to a variety of developmental disorders. For example, mutations in certain HOX genes can cause hand-foot-genital syndrome, a condition characterized by abnormalities in the development of the hands, feet, and reproductive organs. Similarly, mutations in PAX genes can lead to aniridia, a condition characterized by the absence of the colored part of the eye.

See also

• Gene expression
• Morphogenesis
• Developmental biology