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Epimorphosis

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Epimorphosis is defined as the regeneration of a specific part of an organism in a way that involves extensive cell proliferation[1], as well as blastema formation[2]. Epimorphosis can be considered a simple model for development, though it only occurs in tissues surrounding the site of injury rather than occurring system-wide[3].

History of Epimorphosis

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Thomas Hunt Morgan, an evolutionary biologist who also worked with embryology, argued that limb and tissue reformation bore many similarities to embryonic development[4]. Building off of the work of German embryologist Wilhelm Roux, who suggested regeneration was two cooperative but distinct pathways instead of one, Morgan named the two parts of the regenerative process epimorphosis and morphallaxis. Specifically, Morgan wanted epimorphosis to specify the process of entirely new tissues being regrown from an amputation or similar injury, with morphallaxis being coined to describe regeneration that did not use cell proliferation, such as in hydra[5].

The apical ectodermal ridge in embryonic development is very similar to the apical ectodermal cap in limb regeneration. The progress zone can be seen near to the zone of polarizing activity, which instructs cells on how to orient the limb[6].

Epimorphosis in vertebrates

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In vertebrates, epimorphosis relies on blastema formation to proliferate cells into the new tissue. Through studies involving zebrafish fins, the toetips of mice, and limb regeneration in axolotls, researchers at the Polish Academy of Sciences found evidence for epimorphosis occurring in a variety of vertebrates, including instances of mammal epimorphosis[7].

Salamanders

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Immediately after the limb is amputated, a plasma clot forms over the wound. Epidermal cells at the wound margins migrate to cover the wound and will become the wound epidermis.[8] No scar tissue forms, as it would in mammals.

An apical ectodermal cap (AEC) forms on the tip of the stump[9]. This is similar to the embryonic apical ectodermal ridge, which forms during normal limb development. The AEC causes the progress zone to re-establish; this means the cells under the AEC dedifferentiate and become mesenchymal. The AEC releases factors[clarification needed] that drive the development of the new limb, essentially resetting the limb back to its embryonic development stage[citation needed].

But even though some of the limb cells are able to dedifferentiate, they are not able to fully dedifferentiate to the level of multipotent progenitor cells. During regeneration, only cartilage cells can form new cartilage tissue, only muscle cells can form new muscle tissue, and so on. The dedifferentiated cells still retain their original specification.[8]. ]]

Epimorphosis in invertebrates

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Periplaneta americana

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The American cockroach is capable of regenerating limbs that have been damaged or destroyed, such as legs and antennae, as well parts of its compound eye. It does this with a lectin--a protein made for binding proteins--named regenectin, which shares a family with other lipopolysaccharide (LPS) binding proteins. Regenectin carries both a regenerative function and a system defense function, and it is produced by the cockroach's paracrine system to work with muscle reformation[3].

Capitella teleta

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C. teleta is a segmented worm found in North America that is capable of regenerating posterior segments after amputation. This regeneration uses the interaction of several sets of Hox genes, as well as blastema formation. All of the Hox genes concerned in epimorphosis are present in the abdominal area of the worm, but not in the anterior portion. However, the genes do not, themselves, direct the anterior-posterior patterning of the worm's thorax[10].

References

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  1. ^ "Medical Definition of EPIMORPHOSIS". www.merriam-webster.com. Retrieved 2018-02-19.
  2. ^ Yokoyama, Hitoshi (2008-01-01). "Initiation of limb regeneration: The critical steps for regenerative capacity". Development, Growth & Differentiation. 50 (1): 13–22. doi:10.1111/j.1440-169X.2007.00973.x. ISSN 1440-169X.
  3. ^ a b Kubo, T.; Arai, T. (September 1996). "Insect Lectins and Epimorphosis". Trends in Glycoscience and Glycotechnology. 8 (43). Japanese Society of Carbohydrate Research: 357–364.
  4. ^ Sunderland, Mary Evelyn (2010-05-01). "Regeneration: Thomas Hunt Morgan's Window into Development". Journal of the History of Biology. 43 (2): 325–361. doi:10.1007/s10739-009-9203-2. ISSN 0022-5010.
  5. ^ "Thomas Hunt Morgan's Definition of Regeneration: Morphallaxis and Epimorphosis | The Embryo Project Encyclopedia". embryo.asu.edu. Retrieved 2018-02-19.
  6. ^ SUMMERBELL, D.; LEWIS, J. H.; WOLPERT, L. (August 24, 1973). "Positional Information in Chick Limb Morphogenesis". Nature. 244: 492–496. doi:10.1038/244492a0. ISSN 1476-4687.
  7. ^ Animal models for the study of human disease. Conn, P. Michael, (Second edition ed.). London, United Kingdom. ISBN 9780128096994. OCLC 992170104. {{cite book}}: |edition= has extra text (help)CS1 maint: extra punctuation (link) CS1 maint: others (link)
  8. ^ a b Scott F. Gilbert, Developmental Biology Tenth Edition. Sinauer Associates, Inc. Sunderland, MA, USA, 2014. pp 571–573
  9. ^ Issues in Biological, Biochemical, and Evolutionary Sciences Research: 2011 Edition. Atlanta, GA: ScholarlyEditions. 2012. p. 464.
  10. ^ de Jong, Danielle M.; Seaver, Elaine C. (2016-02-19). "A Stable Thoracic Hox Code and Epimorphosis Characterize Posterior Regeneration in Capitella teleta". PLoS ONE. 11 (2). doi:10.1371/journal.pone.0149724. ISSN 1932-6203. PMC 4764619. PMID 26894631.{{cite journal}}: CS1 maint: PMC format (link) CS1 maint: unflagged free DOI (link)

Category:Developmental biology Category:Animal anatomy


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Article Evaluations

Epimorphosis

  1. The article is very short and needs more information.
    1. The article only includes information on epimorphosis in salamanders--research needs to be done to see if it occurs in other animals.
  2. The sources included are scant and questionable--sources need to be verified and supplemented with additional reputable sources.
  3. The article could use some editing for clarity and layman understandability.
  4. The article needs its cross-linking strengthened.

Possible sources:

Unifying principles of regeneration

Developmental Biology 6th edition - NCBI Bookshelf

Thomas Hunt Morgan's Definition of Regeneration: Morphallaxis and Epimorphosis - The Embryo Project at Arizona State University

A Stable Thoracic Hox Code and Epimorphosis Characterize Posterior Regeneration in Capitella teleta - PLOSone

The cell biology of regeneration - Journal of Cell Biology

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X hyperactivation

  1. The article is a stub and could use considerably more information, such as the effects that this has on Drosophila and if other organisms also experience this condition.

Pair-rule gene

  1. The article is very short and needs more information on what this type of gene controls, as well as what damaged copies of the gene do to an organism and how those damages might occur.
  2. The article lists several different pair-rule genes, but does not include any out-linking to articles about those genes, if they exist.