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| Homeotic protein antennapedia | |||||||
|---|---|---|---|---|---|---|---|
| Identifiers | |||||||
| Organism | Drosophila melanogaster | ||||||
| Symbol | antp | ||||||
| UniProt | P02833 | ||||||
| |||||||
Antennapedia (abbreviatedAntp) is aHox gene first discovered inDrosophila which controls the formation oflegs during development. Loss-of-functionmutations in theregulatory region of this gene result in the development of the second leg pair intoectopicantennae. By contrast gain-of-functionalleles convert antennae into ectopic legs.[1]
This is just one illustration of the tendency of organisms to exhibit variations on a theme: modulated repetition. Legs and antennae are related to one another as much as molars are to incisors, fingers are to toes, and arms are to legs.
Antp also refers to a gene complex (ANT-C) inDrosophila ending with theAntp gene. It is responsible for formation and differentiation of thethoracic and head segments of the fly's body.
The origin of the ancestorhomeobox gene is an important aspect of the evolution of theAntp-classHox genes. Early evolution of theAntp-class genes may have predated the divergence ofcnidarians. However, the role thatAntp plays in the spatial body development of cnidarians remains unclear. A widely accepted theory is that the ancestorHox cluster containing three genes arose in the earlymetazoan era. It is suggested that Antennapedia arose fromEvx, a non-Hox family of genes. This duplication event ofEvx into theAntp-class probably occurred prior to cnidarian divergence, as there are Cnidarians withEvx and withoutHox class genes and vice versa.[2]
Recent studies have observed thatdown-regulation of theAntp gene inParasteatoda tepidariorum leads to the development of a pair of ectopic legs, resulting in 10-legged mutant spiders.DrosophilaAntp is thought to play an important role in the role of ectopic leg or antenna placement, but not in abdominal leg suppression. However, recent research supported that leg suppression was indeed performed byAntp in arachnids.[3] This suggests that spiders and insects may have separately developed strategies of the leg suppression via the evolutionary pressure of convergence. Arachnids'Antp gene is different from otherAntpHox clusters, suggesting that it has evolved via a divergence event leading to the development on the leg suppression function. This example suggests how the functions of homeobox genes includingAntp have evolved over time to account for different lineages' needs.[3]
Although it is known thatAntp-class homeobox genes play some sort of role intranscriptional processes, not all of their actions and functions have been discovered. Recent studies observedAntp and theHox orthologHoxC6 inXenopus in order to further distinguish the evolution of these orthologues.HoxC6 was found to play an important role ingastrulation in the vertebrateXenopus. However, gastrulation was also a target in theDrosophilaAntp gene. The anterior–posterior pattern mechanism is highly conserved in these genes, as its function inXenopus is clear, but it is unclear why it would be a target inDrosophila. The similarities continuously observed betweenHox genes in vertebrates andDrosophila suggests a complex evolutionary history of theAntpHox gene cluster, as well as reaffirms the importance of the conservation of this gene cluster in the evolution of body morphology.[4]