Difference between revisions of "Developmental Mechanism - Mesenchymal Epithelial Transition"

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Introduction

Gastrulation epithelial to mesenchymal transition

In mesenchymal epithelial transition, mesenchymal cells form an embryonic connective tissue with a disorganised cellular organisation can undergo transition to an epithelial organisation (organised cellular layer) as a developmental process and are said to have undergone a Mesenchymal to Epithelial Transition (MET). This morphological change appears to be the opposite process to that seen in epithelial mesenchymal transition.


Mesenchymal cells, connective tissue-like, that have undergone this process may at a later time and under specific signaling can undergo the opposite process, mesenchyme to epithelia. In development, this process can be repeated several times during tissue differentiation.


Mechanism - "a process, technique, or system for achieving a result".


Mechanism Links: mitosis | cell migration | cell junctions |epithelial invagination | epithelial mesenchymal transition | mesenchymal epithelial transition | epithelial mesenchymal interaction | morphodynamics | tube formation | apoptosis | autophagy | axes formation | time | molecular

Some Recent Findings

  • Mesenchymal-epithelial transition regulates initiation of pluripotency exit before gastrulation[1] "The pluripotent epiblast gives rise to all tissues and organs in the adult body. Its differentiation starts at gastrulation, when the epiblast generates mesoderm and endoderm germ layers through epithelial-mesenchymal transition (EMT). Although gastrulation EMT coincides with loss of epiblast pluripotency, pluripotent cells in development and in vitro can adopt either mesenchymal or epithelial morphology. The relationship between epiblast cellular morphology and its pluripotency is not well understood. Here, using chicken epiblast and mammalian pluripotency stem cell (PSC) models, we show that PSCs undergo a mesenchymal-epithelial transition (MET) prior to EMT-associated pluripotency loss. Epiblast MET and its subsequent EMT are two distinct processes. The former, a partial MET, is associated with reversible initiation of pluripotency exit, whereas the latter, a full EMT, is associated with complete and irreversible pluripotency loss. We provide evidence that integrin-mediated cell-matrix interaction is a key player in pluripotency exit regulation. We propose that epiblast partial MET is an evolutionarily conserved process among all amniotic vertebrates and that epiblast pluripotency is restricted to an intermediate cellular state residing between the fully mesenchymal and fully epithelial states.}
  • Evidence from a Mouse Model That Epithelial Cell Migration and Mesenchymal-Epithelial Transition Contribute to Rapid Restoration of Uterine Tissue Integrity during Menstruation.[2] "In women dynamic changes in uterine tissue architecture occur during each menstrual cycle. Menses, characterised by the shedding of the upper functional layer of the endometrium, is the culmination of a cascade of irreversible changes in tissue function including stromal decidualisation, inflammation and production of degradative enzymes. The molecular mechanisms that contribute to the rapid restoration of tissue homeostasis at time of menses are poorly understood. ...Analysis of mRNAs encoding genes expressed exclusively in the epithelial or stromal compartments, or implicated in MET, revealed dynamic changes in expression, consistent with a role for reprogramming of mesenchymal cells so that they could contribute to re-epithelialisation."
More recent papers  
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Search term: Mesenchymal Epithelial Transition

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.


The alternate process involves the conversion of the embryonic connective tissue organization (mesenchyme) to an epithelial organization (epithelium) that can occur during developmental processes.

This process can be seen occurring during early somitogenesis.


It is also suggested that this mechanism occurs in the maternal uterus during endometrial regeneration following decidualization.[2]


Links: Mesenchymal Epithelial Transition

Somitogenesis

During early somite formation (somitogenesis) the mesenchymal paraxial mesoderm undergoes a MET to form the initial segment of the somite "ball". This ball of mesoderm has an epithelial outer layer and a core of mesenchyme. The early somite also contains a space, the somitoceol, that is lost as the mesoderm proliferates to form a solid ball.

The somite epithelial layer then breaks down as the somite disperses to form the sclerotome and dermomyotome. The dermomyotome initially remains as an epithelial layer, that also is lost as the dermatome and myotome proliferate and migrate.



Links: Somitogenesis
Stage11 sem100.jpg

Human embryo (week 4, Carnegie stage 11) somites

Renal

Abbreviation
(OMIM link)
Growth Factor
(Factor page link)
Renal Development Expression Location
Wnt9b Wingless-type MMTV integration site family, Member 9B renewal and differentiation of nephron progenitors and normal ureteric bud branching, mesenchymal-to-epithelial transition uteric bud stalk epithelial cells


Links: Renal Molecular | Renal System Development

References

  1. Hamidi S, Nakaya Y, Nagai H, Alev C, Kasukawa T, Chhabra S, Lee R, Niwa H, Warmflash A, Shibata T & Sheng G. (2020). Mesenchymal-epithelial transition regulates initiation of pluripotency exit before gastrulation. Development , 147, . PMID: 32014865 DOI.
  2. 2.0 2.1 Cousins FL, Murray A, Esnal A, Gibson DA, Critchley HO & Saunders PT. (2014). Evidence from a mouse model that epithelial cell migration and mesenchymal-epithelial transition contribute to rapid restoration of uterine tissue integrity during menstruation. PLoS ONE , 9, e86378. PMID: 24466063 DOI.


Textbooks

Reviews

Sannino G, Marchetto A, Kirchner T & Grünewald TGP. (2017). Epithelial-to-Mesenchymal and Mesenchymal-to-Epithelial Transition in Mesenchymal Tumors: A Paradox in Sarcomas?. Cancer Res. , 77, 4556-4561. PMID: 28811330 DOI.

Chaffer CL, Thompson EW & Williams ED. (2007). Mesenchymal to epithelial transition in development and disease. Cells Tissues Organs (Print) , 185, 7-19. PMID: 17587803 DOI.

Articles

Search PubMed

Search Pubmed: Epithelial Mesenchymal Transition

External Links

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Mechanism Links: mitosis | cell migration | cell junctions |epithelial invagination | epithelial mesenchymal transition | mesenchymal epithelial transition | epithelial mesenchymal interaction | morphodynamics | tube formation | apoptosis | autophagy | axes formation | time | molecular


Glossary Links

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Cite this page: Hill, M.A. (2020, October 25) Embryology Developmental Mechanism - Mesenchymal Epithelial Transition. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Developmental_Mechanism_-_Mesenchymal_Epithelial_Transition

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© Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G