Mccoy.484

Wikipedia Article Edits:

https://en.wikipedia.org/wiki/Antennapedia

Origin of Antennapedia Class Homeobox Gene

The origin of the ancestor Homeobox gene is an important aspect of the evolution of the Antp-class Hox genes. Early evolution of the Antp-class genes may have predated the divergence of Cnidarians. However, the role that Antp plays in the spatial body development of Cnidarians remains unclear. A widely accepted theory is that the ancestor Hox cluster containing three genes arose in the early metazoan era. It is suggested that Antennapedia arose from Evx, a non-Hox family of genes. This duplication event of Evx into the Antp-class probably occurred prior to Cnidarian divergence, as there are Cnidarians with Evx and without Hox class genes and vice versa.

Antennapedia in Arachnids

Recent studies have observed that down-regulation of the Antp gene in Achaearanea tepidariorum leads to the development of a pair of ectopic legs, resulting in 10-legged mutant spiders. Drosophila Antp 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 by Antp in arachnids (Khadjeh 20112). This suggests that spiders and insects may have separately developed strategies of leg suppression via the evolutionary pressure of convergence. Arachnid’s Antp gene is different from other Antp Hox 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 including Antp have evolved overtime to account for different lineages’ needs.

HoxC6: An Ortholog of Antp

Although it is known that Antp-class homeobox genes play some sort of role in transcriptional processes, not all of their actions and functions have been discovered. Recent studies observed Antp and the Hox ortholog HoxC6 in Xenopus in order to further distinguish the evolution of these orthologues. HoxC6 was found to play an important role in gastrulation in the vertebrate Xenopus. However, gastrulation was also a target in the Drosophila Antp gene. The anterior-posterior pattern mechanism is highly conserved in these genes, as its function in Xenopus is clear, but it is unclear why it would be a target in Drosophila. The similarities continuously observed between Hox genes in vertebrates and Drosophila suggests a complex evolutionary history of the Antp Hox gene cluster, as well as reaffirms the importance of the conservation of this gene cluster in the evolution of body morphology.

References

Final Paper:

Evolution of the Antennapedia-Class Homeobox Genes Across Species

Erica McCoy Tues 12:40

Antennapedia is a Homeobox gene, which controls body organization and segmentation during development. It has been highly conserved in both vertebrates as well as insects such as Drosophila Melanogaster. It plays an important role in the body development along the anterior-posterior axis. The evolution of the Antp-Homeobox gene cluster can explain the body development of both invertebrates and vertebrates, and consequently demonstrate the evolutionary relationships between these species. Homeobox genes control the body development and segmentation of organisms from the anterior to posterior axis. In insects, including Drosophila melanogaster, the cluster of homeobox genes including Antennapedia is located on the same chromosome, while in humans, the clusters are found in four clusters on different chromosomes. The clusters of genes correlate spatially with the body development patterning from anterior to posterior. Hox genes are thought to be important transcription factors and are key in the early developmental stages of body organization. A mutation in the Hox gene Antp in Drosophila can result in ectopic legs in the place of antennae and vice versa. Similarly, this mutation found in A. tepidariorum, can result in 10-legged spiders (Khadjeh et al 2012). These dramatic mutations support that Antp alone, as well as the other Hox gene clusters are critical in body development. Antp has evolved into 13 paralogous groups of genes in vertebrates that can further be divided into Group I and Group II. Group I genes can be subdivided into subgroups A, B, and C, and Group II is subdivided into subgroups D and E. (Zhang and Nei 1996). Scientists used phylogenetic trees to explain how these gene groups may have diverged. Zhang speculated that Group I and II’s ancestor gene originated from a gene duplication event. The divergence of the group I and group II gene clusters is thought to have occurred around 1000 million years ago. Zhang also hypothesized that the subgroups in both Group I and Group II diverged around 600 million years ago, as a result of both gene duplication and deletion events. Because these 13 gene clusters are thought to have arose prior to vertebrate radiation, it supports why they are so similar in different vertebrates. (Zhang and Nei 1996). Similarities in Hox gene Antp nucleotide sequences are one way to determine the relatedness of different species. For example, Kappen wanted to determine how closely related the mice and human homeobox genes were to one another, as well as their relatedness to Drosophila. It was found that 94% of the nucleotides in the human and mice Homeobox genes that were different were silent mutations, supporting that theses gene clusters were derived from a common ancestor. The average number of nucleotide differences observed between human and mice species was significantly lower than the difference between two different mice species, suggesting that the divergence of the four clusters of Homeobox genes in vertebrates occurred earlier than the divergence of the species of mice and humans (Kappen et al 1989). This method, along with others such as phylogenetic trees, has been used to find how Hox genes have evolved and consequently the relatedness of species. Evolution of Homeobox clusters occurred in two distinct phases. First, there was the expansion of the primordial complex. A high percentage of nucleotide differences resulted from substitution events, demonstrating that this period of evolution was rapid. This evolutionary pressure accounted for the divergence of the different homeoboxes. The second phase of evolution occurred when there was high conservation of amino acid sequences in the gene clusters that arose from duplication. This supported evolutionary pressure to conserve the genes, as most of the mutations that arose were silent mutations; they did not have any effect on altering the function of the gene and maintained the integrity of the ancestor Homeobox gene. (Kappen et al 1989). The origin of the ancestor Homeobox gene is another important aspect of the evolution of the Antp-class Hox genes. Early evolution of the Antp-class genes may have predated the divergence of Cnidarians. However, the role that Antp plays in the spatial body development of Cnidarians remains unclear. A widely accepted theory is that the ancestor Hox cluster containing three genes arose in the early metazoan era. It is suggested that Antp arose from Evx, a non-Hox family of genes. This duplication event of Evx into the Antp-class probably occurred prior to Cnidarian divergence, as there are Cnidarians with Evx and without Hox class genes and vice versa (Gauchat et al 2000.) PCR techniques demonstrate that Cnidarian Antp-class genes are most closely related to the 3’ portion of higher organisms’ Antp gene. The 3’ end of the gene cluster controls anterior body development. Antp-gene duplication events may have occurred in an order from anterior to posterior or 3’ to 5’. Furthermore, this could implicate that segmentation evolution may have occurred from anterior to posterior (Murtha 1991). Another important event in the evolution of the Antp class homeobox genes is the development of the paralogs in Drosophila and vertebrates. While vertebrates have 13 groups of Antp genes, Drosophila have only 11 Antp genes. Schubert illustrates that Drosophila and vertebrate Homeobox clusters arose from a common homeobox cluster. The last common ancestor of insects and vertebrates had a cluster of five Homeobox genes as a result of gene duplication. Then, the vertebrates four gene clusters and Drosophila’s single Hox gene cluster arose in independent events (Schubert et al. 1993). Not only has the evolution of Antp class homeobox gene clusters occurred, but the action of these genes has changed as well. For instance, Drosophila Antp was thought to play an important role in the role of ectopic leg or antenna placement, but not in abdominal leg suppression. However, Khadjeh’s research supported that leg suppression was indeed performed by Antp in arachnids (Khadjeh 20112). This suggests that spiders and insects may have separately developed strategies of leg suppression via the evolutionary pressure of convergence. Furthermore, apart from the homeodomain in arachnid’s Antp gene, it is very different from other Antp Hox clusters, suggesting that it has evolved via a divergence event leading to the development on the leg suppression function. This example, along with others, suggests how the functions of homeobox genes including Antp have evolved overtime to account for different lineages’ needs. Although it is known that Antp-class homeobox genes play some sort of role in transcriptional processes, not all of their actions and functions have been discovered. Michaut observed Antp and the Hox ortholog HoxC6 in Xenopus in order to further distinguish the evolution of these orthologues. HoxC6 was found to play an important role in gastrulation in the vertebrate Xenopus (Michaut et al 2011). However, gastrulation was also a target in the Drosophila Antp gene. The anterior-posterior pattern mechanism is highly conserved in these genes, as its function in Xenopus is clear, but it is unclear why it would be a target in Drosophila. The similarities continuously observed between Hox genes in vertebrates and Drosophila suggests a complex evolutionary history of the Antp Hox gene cluster, as well as reaffirms the importance of the conservation of this gene cluster in the evolution of body morphology. Gene regulation is another important facet of Antp-class Hox gene function evolution to consider. Holland proposed that majority of Hox gene functions that are related within a species arose from an ancestral gene with a similar function. However, it is likely that differences in function arose after gene duplication events took place. Differences typically resulted from functional gains that arose in order to account for increased complexity in the spatial development of organisms (Holland 1992). The evolution of the Antp-class Homeobox genes is an expansive field and can explain the evolutionary relationships between invertebrates and vertebrates. The conservation of Hox genes demonstrates their importance across species in body development. Furthermore, their diverse functions in transcription suggest divergence amongst species and a complex evolutionary history over millions of years. Exploration of the Antp-class Homeobox genes will further explain how body development has been an important factor that evolutionary pressure has impacted. References

Gauchat D, Mazet F, Berney C, Schummer M, Kreger S, Pawlowski J and Galliot B. Evolution of Antp-Class Genes and Differential Expression of Hydra Hox/ParaHox Genes in Anterior Patterning. Proceedings of the National Academy of Sciences of the United States of America, Vol. 97, No. 9 (Apr. 25, 2000), pp. 4493-4498

Holland, Peter. 1992. "Problems and paradigms: Hoemeobox genes in vertebrate evolution". BioEssays. 14 (4): 267-273.

Kappen C, Schughart K and Ruddle F. Two Steps in the Evolution of Antennapedia-Class Vertebrate Homeobox Genes. Proceedings of the National Academy of Sciences of the United States of America Vol. 86, No. 14 (Jul. 15, 1989) , pp. 5459-5463

Khadjeh S, Turetzek N, Pechmann M, Schwager E, Wimmer E, Damen WGM, Prpic N. Divergent role of the Hox gene Antennapedia in spiders is responsible for the convergent evolution of abdominal limb repression. PNAS 2012 109 (13) 4921-4926; published ahead of print March 15, 2012, doi:10.1073/pnas.1116421109

Michaut L, Jansen HJ, Bardine N, Durston AJ, Gehring WJ. Analyzing the function of a hox gene: an evolutionary approach. Dev Growth Differ. 2011;53:993.

Murtha M, Leckman J and Frank H. Ruddle. Detection of Homeobox Genes in Development and Evolution. Proceedings of the National Academy of Sciences of the United States of America, Vol. 88, No. 23 (Dec. 1, 1991), pp. 10711-10715

Schubert F, Nieselt-Struwe K and Gruss P. The Antennapedia-Type Homeobox Genes have Evolved from Three Precursors Separated Early in Metazoan Evolution . Proceedings of the National Academy of Sciences of the United States of America Vol. 90, No. 1 (Jan. 1, 1993) , pp. 143-147

Zhang J and Nei M. Evolution of Antennapedia-Class Homeobox Genes. Institute of Molecular Evolutionaly Genetics and Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 1996 January; 142(1): 295–303.

Article I edited/commented on:

https://en.wikipedia.org/wiki/Antennapedia

Sentence I added:

Recent studies have observed that down-regulation of the Antp gene in Achaearanea tepidariorum leads to the development of a pair of ectopic legs, resulting in 10-legged mutant spiders.

Citation:

Sara Khadjeh, Natascha Turetzek, Matthias Pechmann, Evelyn E. Schwager, Ernst A. Wimmer, Wim G. M. Damen, and Nikola-Michael Prpic Divergent role of the Hox gene Antennapedia in spiders is responsible for the convergent evolution of abdominal limb repression PNAS 2012 109 (13) 4921-4926; published ahead of print March 15, 2012, doi:10.1073/pnas.1116421109

Talk Section Suggestions:

This page could be improved in a variety of ways.

First, it could expand its content in general. It should mention that Antp is not only present in Drosophila, but also other organisms. Its function varies from one organism to another, but across organisms the Antp gene is involved in body segment development and differentiation. Furthermore, it could discuss the evolution of Antp, and how it demonstrates divergence of species.

In the first paragraph, it could be more explicit that it is explaining how the Antp gene affects body segmentation development in Drosophila. It could explain that the Antp mutation has been extensively studied in Drosophila, but that is not to say that Antp gene expression does not have functions and mutations in other organisms. In fact, in spiders, down-regulation of Antp results in 10-legged spiders.

"Antennapedia also refers to a gene complex in Drosophila which is responsible for formation and differentiation of the thoracic and head segments of the fly's body." This is a confusing statement and could be changed. It could state that Antennapedia refers to a Hox gene complex in Drosophila (and other arthropods, insects, etc.) which is responsible for body segment development. In drosophila in particular, it is responsible for formation and differentiation of thoracic and head segments, and, as a result, differentiation of leg and antenna development. Beginning with this statement and then later on mentioning the gain/loss of function mutation in Drosophila could make this article less confusing for someone who is trying to understand the Hox gene Antp.

Mccoy.484 (talk) 18:48, 30 September 2014 (UTC)mccoy.484

________________________

Topic for Wikipedia report:

Evolution of the Antennapedia-class Homeobox gene across species

Annotated Bibliography:

1. Two Steps in the Evolution of Antennapedia-Class Vertebrate Homeobox Genes Claudia Kappen, Klaus Schughart and Frank H. Ruddle Proceedings of the National Academy of Sciences of the United States of America Vol. 86, No. 14 (Jul. 15, 1989) , pp. 5459-5463

Although this article is dated, it provides a thorough explanation of the specific nucleotide sequence evolution of the Antennapedia gene class.

2. The Antennapedia-Type Homeobox Genes have Evolved from Three Precursors Separated Early in Metazoan Evolution Frank R. Schubert, Katja Nieselt-Struwe and Peter Gruss Proceedings of the National Academy of Sciences of the United States of America Vol. 90, No. 1 (Jan. 1, 1993) , pp. 143-147

This article discusses that Antp had an important function even in the Metazoan era, and how this led to different paralogues of the Antp gene.

3. Evolution of Antennapedia-Class Homeobox Genes Jianzhi Zhang and Masatoshi Nei Institute of Molecular Evolutionaly Genetics and Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802 1996 January; 142(1): 295–303.

Another dated article, but it discusses how the Antp-class homebox is evidence for coevolution and divergence of certain species.

4. Evolution of Antp-Class Genes and Differential Expression of Hydra Hox/ParaHox Genes in Anterior Patterning Dominique Gauchat, Francoise Mazet, Cedric Berney, Michel Schummer, Sylvia Kreger, Jan Pawlowski and Brigitte Galliot Proceedings of the National Academy of Sciences of the United States of America, Vol. 97, No. 9 (Apr. 25, 2000), pp. 4493-4498

This article discusses evolution of Antp in hydra and how it provides evidence for the coevolution and divergence of species using phylogenetic analysis.

5. Divergent role of the Hox gene Antennapedia in spiders is responsible for the convergent evolution of abdominal limb repression Sara Khadjeh, Natascha Turetzek, Matthias Pechmann, Evelyn E. Schwager, Ernst A. Wimmer, Wim G. M. Damen, and Nikola-Michael Prpic PNAS 2012 109 (13) 4921-4926; published ahead of print March 15, 2012, doi:10.1073/pnas.1116421109

This article contains the most recent research on Antp and discusses evidence for convergent evolution in spiders.