Developmental Mechanism - Mesenchymal Epithelial Transition

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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 | epithelial invagination | epithelial mesenchymal transition | mesenchymal epithelial transition | epithelial mesenchymal interaction | morphodynamics | tube formation | apoptosis | autophagy | axes formation | time | molecular

Some Recent Findings

  • Evidence from a Mouse Model That Epithelial Cell Migration and Mesenchymal-Epithelial Transition Contribute to Rapid Restoration of Uterine Tissue Integrity during Menstruation.[1] "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."
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Search term: Mesenchymal Epithelial Transition

<pubmed limit=5> Mesenchymal Epithelial Transition</pubmed>

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.[1][2]

Links: Mesenchymal Epithelial Transition


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


(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


  1. 1.0 1.1 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. Cite error: Invalid <ref> tag; name "PMID24466063" defined multiple times with different content
  2. <pubmed>23216285</pubmed>





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

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Cite this page: Hill, M.A. (2019, September 24) Embryology Developmental Mechanism - Mesenchymal Epithelial Transition. Retrieved from

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