1
|
Moazzen H, Bolaji MD, Leube RE. Desmosomes in Cell Fate Determination: From Cardiogenesis to Cardiomyopathy. Cells 2023; 12:2122. [PMID: 37681854 PMCID: PMC10487268 DOI: 10.3390/cells12172122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 08/16/2023] [Accepted: 08/17/2023] [Indexed: 09/09/2023] Open
Abstract
Desmosomes play a vital role in providing structural integrity to tissues that experience significant mechanical tension, including the heart. Deficiencies in desmosomal proteins lead to the development of arrhythmogenic cardiomyopathy (AC). The limited availability of preventative measures in clinical settings underscores the pressing need to gain a comprehensive understanding of desmosomal proteins not only in cardiomyocytes but also in non-myocyte residents of the heart, as they actively contribute to the progression of cardiomyopathy. This review focuses specifically on the impact of desmosome deficiency on epi- and endocardial cells. We highlight the intricate cross-talk between desmosomal proteins mutations and signaling pathways involved in the regulation of epicardial cell fate transition. We further emphasize that the consequences of desmosome deficiency differ between the embryonic and adult heart leading to enhanced erythropoiesis during heart development and enhanced fibrogenesis in the mature heart. We suggest that triggering epi-/endocardial cells and fibroblasts that are in different "states" involve the same pathways but lead to different pathological outcomes. Understanding the details of the different responses must be considered when developing interventions and therapeutic strategies.
Collapse
Affiliation(s)
- Hoda Moazzen
- Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany; (M.D.B.); (R.E.L.)
| | | | | |
Collapse
|
2
|
The Mammary Gland: Basic Structure and Molecular Signaling during Development. Int J Mol Sci 2022; 23:ijms23073883. [PMID: 35409243 PMCID: PMC8998991 DOI: 10.3390/ijms23073883] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/22/2022] [Accepted: 03/30/2022] [Indexed: 01/27/2023] Open
Abstract
The mammary gland is a compound, branched tubuloalveolar structure and a major characteristic of mammals. The mammary gland has evolved from epidermal apocrine glands, the skin glands as an accessory reproductive organ to support postnatal survival of offspring by producing milk as a source of nutrition. The mammary gland development begins during embryogenesis as a rudimentary structure that grows into an elementary branched ductal tree and is embedded in one end of a larger mammary fat pad at birth. At the onset of ovarian function at puberty, the rudimentary ductal system undergoes dramatic morphogenetic change with ductal elongation and branching. During pregnancy, the alveolar differentiation and tertiary branching are completed, and during lactation, the mature milk-producing glands eventually develop. The early stages of mammary development are hormonal independent, whereas during puberty and pregnancy, mammary gland development is hormonal dependent. We highlight the current understanding of molecular regulators involved during different stages of mammary gland development.
Collapse
|
3
|
Meinsohn MC, Hughes CHK, Estienne A, Saatcioglu HD, Pépin D, Duggavathi R, Murphy BD. A role for orphan nuclear receptor liver receptor homolog-1 (LRH-1, NR5A2) in primordial follicle activation. Sci Rep 2021; 11:1079. [PMID: 33441767 PMCID: PMC7807074 DOI: 10.1038/s41598-020-80178-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 12/17/2020] [Indexed: 02/07/2023] Open
Abstract
Liver receptor homolog-1 (NR5A2) is expressed specifically in granulosa cells of developing ovarian follicles where it regulates the late stages of follicle development and ovulation. To establish its effects earlier in the trajectory of follicular development, NR5A2 was depleted from granulosa cells of murine primordial and primary follicles. Follicle populations were enumerated in neonates at postnatal day 4 (PND4) coinciding with the end of the formation of the primordial follicle pool. The frequency of primordial follicles in PND4 conditional knockout (cKO) ovaries was greater and primary follicles were substantially fewer relative to control (CON) counterparts. Ten-day in vitro culture of PND4 ovaries recapitulated in vivo findings and indicated that CON mice developed primary follicles in the ovarian medulla to a greater extent than did cKO animals. Two subsets of primordial follicles were observed in wildtype ovaries: one that expressed NR5A2 and the second in which the transcript was absent. Neither expressed the mitotic marker. KI-67, indicating their developmental quiescence. RNA sequencing on PND4 demonstrated that loss of NR5A2 induced changes in 432 transcripts, including quiescence markers, inhibitors of follicle activation, and regulators of cellular migration and epithelial-to-mesenchymal transition. These experiments suggest that NR5A2 expression poises primordial follicles for entry into the developing pool.
Collapse
Affiliation(s)
- Marie-Charlotte Meinsohn
- Centre de recherche en reproduction et fertilité, Université de Montréal, 3200 rue Sicotte, St-Hyacinthe, QC, J2S 7C6, Canada
| | - Camilla H K Hughes
- Centre de recherche en reproduction et fertilité, Université de Montréal, 3200 rue Sicotte, St-Hyacinthe, QC, J2S 7C6, Canada
| | - Anthony Estienne
- Centre de recherche en reproduction et fertilité, Université de Montréal, 3200 rue Sicotte, St-Hyacinthe, QC, J2S 7C6, Canada
| | - Hatice D Saatcioglu
- Pediatric Surgical Research Laboratories, Simches Research Center, Massachusetts General Hospital, 185 Cambridge St., Boston, MA, 02114, USA
| | - David Pépin
- Pediatric Surgical Research Laboratories, Simches Research Center, Massachusetts General Hospital, 185 Cambridge St., Boston, MA, 02114, USA
| | - Raj Duggavathi
- Department of Animal Science, McGill University, 21111 Lakeshore Rd., MS1085, Ste-Anne de Bellevue, QC, H9X 3V9, Canada
| | - Bruce D Murphy
- Centre de recherche en reproduction et fertilité, Université de Montréal, 3200 rue Sicotte, St-Hyacinthe, QC, J2S 7C6, Canada.
| |
Collapse
|
4
|
Fukuda S, Akiyama M, Harada H, Nakahama KI. Effect of gap junction-mediated intercellular communication on TGF-β induced epithelial-to-mesenchymal transition. Biochem Biophys Res Commun 2018; 508:928-933. [PMID: 30545634 DOI: 10.1016/j.bbrc.2018.12.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 12/05/2018] [Indexed: 02/08/2023]
Abstract
Epithelial-to-mesenchymal transition (EMT) is the process in which epithelial cells lose cell polarity and cell adhesion with surrounding cells to obtain migratory and invasive abilities. On the other hand, the expression of connexin is decreased or lacked in the many types of tumor cells. This study examined the effect of gap junctional intercellular communication (GJIC) on EMT induced by the transforming growth factor-β1 (TGF-β1). To investigate the effect of GJIC on EMT in U2OS cells, smooth muscle 22-α (sm22α) promoter-driven luciferase reporter gene was introduced into Cx43-expressing cells (U2OS-Luc Cx43) and into the control parental cell line (U2OS-Luc). TGF-β1 induced the expression of EMT markers and the sm22α promoter activity of U2OS-Luc cells. Sm22α promoter activity of U2OS cells was neither dependent on the expression of Cx43 nor on the establishment of GJIC among U2OS cells. Furthermore, we found that the homocellular communication among tumor cells did not affected the tumor cell growth and migration. However, we revealed that tumor cell density was an important factor for tumor cells to acquire metastatic phenotype. Interestingly, the co-culture of U2OS cells with osteoblasts revealed that sm22α promoter activity was inhibited only by the GJIC established between these two cell types. These results suggest that normal osteoblast cells negatively regulate the EMT of tumor cells, at least in part. Thus, Cx43-mediated GJIC may have anti-metastatic activity in tumor cells. Our findings provide a new insight into the role of GJIC in cancer progression and metastasis and identify potential therapeutic targets for the treatment of cancer.
Collapse
Affiliation(s)
- Shuhei Fukuda
- Department of Cellular Physiological Chemistry, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan; Department of Oral and Maxillofacial Surgery, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Masako Akiyama
- Research Administration Division, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Hiroyuki Harada
- Department of Oral and Maxillofacial Surgery, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan
| | - Ken-Ichi Nakahama
- Department of Cellular Physiological Chemistry, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo, 113-8510, Japan.
| |
Collapse
|
5
|
Krishna L, Dhamodaran K, Subramani M, Ponnulagu M, Jeyabalan N, Krishna Meka SR, Jayadev C, Shetty R, Chatterjee K, Khora SS, Das D. Protective Role of Decellularized Human Amniotic Membrane from Oxidative Stress-Induced Damage on Retinal Pigment Epithelial Cells. ACS Biomater Sci Eng 2018; 5:357-372. [DOI: 10.1021/acsbiomaterials.8b00769] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Lekshmi Krishna
- Stem Cell Research Lab, GROW Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
- School of Bioscience and Technology, VIT University, Vellore, Tamil Nadu, India
| | - Kamesh Dhamodaran
- Stem Cell Research Lab, GROW Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Murali Subramani
- Stem Cell Research Lab, GROW Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Murugeswari Ponnulagu
- Stem Cell Research Lab, GROW Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Nallathambi Jeyabalan
- Grow Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Sai Rama Krishna Meka
- Department of Materials Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | - Chaitra Jayadev
- Department of Vitreo-retinal Services, Narayana Nethralaya Eye Institute, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Rohit Shetty
- Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Institute, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| | - Kaushik Chatterjee
- Department of Materials Engineering, Indian Institute of Science, Bangalore, Karnataka, India
| | | | - Debashish Das
- Stem Cell Research Lab, GROW Laboratories, Narayana Nethralaya Foundation, 258/A, Bommasandra Industrial Area, Bangalore, Karnataka, India
| |
Collapse
|
6
|
Gap junction protein Connexin-43 is a direct transcriptional regulator of N-cadherin in vivo. Nat Commun 2018; 9:3846. [PMID: 30242148 PMCID: PMC6155008 DOI: 10.1038/s41467-018-06368-x] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 08/29/2018] [Indexed: 11/16/2022] Open
Abstract
Connexins are the primary components of gap junctions, providing direct links between cells under many physiological processes. Here, we demonstrate that in addition to this canonical role, Connexins act as transcriptional regulators. We show that Connexin 43 (Cx43) controls neural crest cell migration in vivo by directly regulating N-cadherin transcription. This activity requires interaction between Cx43 carboxy tail and the basic transcription factor-3, which drives the translocation of Cx43 tail to the nucleus. Once in the nucleus they form a complex with PolII which directly binds to the N-cadherin promoter. We found that this mechanism is conserved between amphibian and mammalian cells. Given the strong evolutionary conservation of connexins across vertebrates, this may reflect a common mechanism of gene regulation by a protein whose function was previously ascribed only to gap junctional communication. Connexins are components of gap junctions that link cells and allow intercellular communication. Here, the authors show that the Connexin 43 carboxy tail interacts with basic transcription factor-3, leading to nuclear translocation and direct regulation of N-cadherin expression and neural crest migration.
Collapse
|
7
|
James CC, Zeitz MJ, Calhoun PJ, Lamouille S, Smyth JW. Altered translation initiation of Gja1 limits gap junction formation during epithelial-mesenchymal transition. Mol Biol Cell 2018; 29:797-808. [PMID: 29467255 PMCID: PMC5905293 DOI: 10.1091/mbc.e17-06-0406] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Epithelial-mesenchymal transition (EMT) is activated during development, wound healing, and pathologies including fibrosis and cancer metastasis. Hallmarks of EMT are remodeling of intercellular junctions and adhesion proteins, including gap junctions. The GJA1 mRNA transcript encoding the gap junction protein connexin43 (Cx43) has been demonstrated to undergo internal translation initiation, yielding truncated isoforms that modulate gap junctions. The PI3K/Akt/mTOR pathway is central to translation regulation and is activated during EMT, leading us to hypothesize that altered translation initiation would contribute to gap junction loss. Using TGF-β-induced EMT as a model, we find reductions in Cx43 gap junctions despite increased transcription and stabilization of Cx43 protein. Biochemical experiments reveal suppression of the internally translated Cx43 isoform, GJA1-20k in a Smad3 and ERK-dependent manner. Ectopic expression of GJA1-20k does not halt EMT, but is sufficient to rescue gap junction formation. GJA1-20k localizes to the Golgi apparatus, and using superresolution localization microscopy we find retention of GJA1-43k at the Golgi in mesenchymal cells lacking GJA1-20k. NativePAGE demonstrates that levels of GJA1-20k regulate GJA1-43k hexamer oligomerization, a limiting step in Cx43 trafficking. These findings reveal alterations in translation initiation as an unexplored mechanism by which the cell regulates Cx43 gap junction formation during EMT.
Collapse
Affiliation(s)
- Carissa C James
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Graduate Program in Translational Biology, Medicine, and Health, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Michael J Zeitz
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016
| | - Patrick J Calhoun
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Samy Lamouille
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016
| | - James W Smyth
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA 24016.,Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| |
Collapse
|
8
|
Zhang Y, Tan X, Xue L. The alpha2-adrenoreceptor agonist dexmedetomidine protects against lipopolysaccharide-induced apoptosis via inhibition of gap junctions in lung fibroblasts. Biochem Biophys Res Commun 2017; 495:92-97. [PMID: 29101030 DOI: 10.1016/j.bbrc.2017.10.162] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 10/29/2017] [Indexed: 01/20/2023]
Abstract
The α2-adrenoceptor inducer dexmedetomidine protects against acute lung injury (ALI), but the mechanism of this effect is largely unknown. The present study investigated the effect of dexmedetomidine on apoptosis induced by lipopolysaccharide (LPS) and the relationship between this effect and gap junction intercellular communication in human lung fibroblast cell line. Flow cytometry was used to detect apoptosis induced by LPS. Parachute dye coupling assay was used to measure gap junction function, and western blot analysis was used to determine the expression levels of connexin43 (Cx43). The results revealed that exposure of human lung fibroblast cell line to LPS for 24 h increased the apoptosis, and pretreatment of dexmedetomidine and 18α-GA significantly reduced LPS-induced apoptosis. Dexmedetomidine exposure for 1 h inhibited gap junction function mainly via a decrease in Cx43 protein levels in human lung fibroblast cell line. These results demonstrated that the inhibition of gap junction intercellular communication by dexmedetomidine affected the LPS-induced apoptosis through inhibition of gap junction function by reducing Cx43 protein levels. The present study provides evidence of a novel mechanism underlying the effects of analgesics in counteracting ALI.
Collapse
Affiliation(s)
- Yuan Zhang
- Department of Pharmacy, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan 511518, People's Republic of China.
| | - Xiaoming Tan
- Department of Pharmacy, The Sixth Affiliated Hospital of Guangzhou Medical University, Qingyuan People's Hospital, Qingyuan 511518, People's Republic of China
| | - Lianfang Xue
- Department of Pharmacy, The First Affiliated Hospital of Jinan University, Guangzhou 510630, People's Republic of China
| |
Collapse
|
9
|
Leithe E. Regulation of connexins by the ubiquitin system: Implications for intercellular communication and cancer. Biochim Biophys Acta Rev Cancer 2016; 1865:133-46. [DOI: 10.1016/j.bbcan.2016.02.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 01/15/2016] [Accepted: 02/04/2016] [Indexed: 12/31/2022]
|
10
|
Cordeiro CR, Alfaro TM, Freitas S, Cemlyn-Jones J. Idiopathic pulmonary fibrosis. Lung Cancer 2015. [DOI: 10.1183/2312508x.10009414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
11
|
Sirnes S, Lind GE, Bruun J, Fykerud TA, Mesnil M, Lothe RA, Rivedal E, Kolberg M, Leithe E. Connexins in colorectal cancer pathogenesis. Int J Cancer 2014; 137:1-11. [PMID: 24752574 DOI: 10.1002/ijc.28911] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 03/11/2014] [Indexed: 12/17/2022]
Abstract
The connexins constitute a family of integral membrane proteins that form channels between adjacent cells. These channels are assembled in plasma membrane domains known as gap junctions and enable cells to directly exchange ions and small molecules. Intercellular communication via gap junctions plays important roles in regulating cell growth and differentiation and in maintaining tissue homeostasis. This type of cell communication is often impaired during cancer development, and several members of the connexin protein family have been shown to act as tumor suppressors. Emerging evidence suggests that the connexin protein family has important roles in colorectal cancer development. In the normal colonic epithelial tissue, three connexin isoforms, connexin 26 (Cx26), Cx32 and Cx43, have been shown to be expressed at the protein level. Colorectal cancer development is associated with loss of connexin expression or relocalization of connexins from the plasma membrane to intracellular compartments. Downregulation of connexins in colorectal carcinomas at the transcriptional level involves cancer-specific promoter hypermethylation. Recent studies suggest that Cx43 may constrain growth of colon cancer cells by interfering with the Wnt/β-catenin pathway. There is also increasing evidence that the connexins may have potential as prognostic markers in colorectal cancer. This review discusses the role of connexins in colorectal cancer pathogenesis, as well as their potential as prognostic markers and targets in the prevention and treatment of the disease.
Collapse
Affiliation(s)
- Solveig Sirnes
- Department of Cancer Prevention, Institute for Cancer Research, Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Faculty of Medicine, Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Changes in Cx43 and NaV1.5 expression precede the occurrence of substantial fibrosis in calcineurin-induced murine cardiac hypertrophy. PLoS One 2014; 9:e87226. [PMID: 24498049 PMCID: PMC3909068 DOI: 10.1371/journal.pone.0087226] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 12/20/2013] [Indexed: 11/19/2022] Open
Abstract
In mice, the calcium-dependent phosphatase calcineurin A (CnA) induces a transcriptional pathway leading to pathological cardiac hypertrophy. Interestingly, induction of CnA has been frequently noticed in human hypertrophic and failing hearts. Independently, the arrhythmia vulnerability of such hearts has been regularly associated with remodeling of parameters determining electrical conduction (expression level of connexin43 (Cx43) and NaV1.5, connective tissue architecture), for which the precise molecular basis and sequence of events is still unknown. Recently, we observed reduced Cx43 and NaV1.5 expression in 4-week old mouse hearts, overexpressing a constitutively active form of CnA (MHC-CnA model), but the order of events is still unknown. Therefore, three key parameters of conduction (Cx43, NaV1.5 and connective tissue expression) were characterized in MHC-CnA ventricles versus wild-type (WT) during postnatal development on a weekly basis. At postnatal week 1, CnA overexpression induced cardiac hypertrophy in MHC-CnA. Moreover, protein and RNA levels of both Cx43 and NaV1.5 were reduced by at least 50% as compared to WT. Cx43 immunoreactive signal was reduced at week 2 in MHC-CnA. At postnatal week 3, Cx43 was less phosphorylated and RNA level of Cx43 normalized to WT values, although the protein level was still reduced. Additionally, MHC-CnA hearts displayed substantial fibrosis relative to WT, which was accompanied by increased RNA levels for genes previously associated with fibrosis such as Col1a1, Col1a2, Col3a1, Tgfb1, Ctgf, Timp1 and microRNA miR-21. In MHC-CnA, reduction in Cx43 and NaV1.5 expression thus coincided with overexpression of CnA and hypertrophy development and preceded significant presence of fibrosis. At postnatal week 4 the alterations in conductional parameters observed in the MHC-CnA model lead to abnormal conduction and arrhythmias, similar to those observed in cardiac remodeling in heart failure patients. The MHC-CnA model, therefore, provides for a unique model to resolve the molecular origin of conductional remodeling in detail.
Collapse
|
13
|
Ke Q, Li L, Cai B, Liu C, Yang Y, Gao Y, Huang W, Yuan X, Wang T, Zhang Q, Harris AL, Tao L, Xiang AP. Connexin 43 is involved in the generation of human-induced pluripotent stem cells. Hum Mol Genet 2013; 22:2221-33. [PMID: 23420013 DOI: 10.1093/hmg/ddt074] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Although somatic cells can be successfully programmed to create pluripotent stem cells by ectopically expressing defined transcriptional factors, reprogramming efficiency is low and the reprogramming mechanism remains unclear. Previous reports have shown that almost all human connexin (CX) isoforms are expressed by human embryonic stem (hES) cells and that gap junctional intercellular communication (GJIC) is important for ES cell survival and differentiation. However, the CX expression profiles in human induced pluripotent stem (iPS) cells and the role of CXs in the process of reprogramming back to iPS cells remains unknown. Here, we determined the expression levels of most forms of CX in human embryonic fibroblasts (hEFs) and in the hEF-derived iPS cells. A scrape loading/dye transfer assay showed that human iPS cells contained functional gap junctions (GJs) that could be affected by pharmacological inhibitors of GJ function. We found that CX43 was the most dramatically upregulated CX following reprogramming. Most importantly, the ectopic expression of CX43 significantly enhanced the reprogramming efficiency, whereas shRNA-mediated knockdown of endogenous CX43 expression greatly reduced the efficiency. In addition, we found that CX43 overexpression or knockdown affected the expression of E-CADHERIN, a marker of the mesenchymal-to-epithelial transition (MET), during reprogramming. In conclusion, our data indicate that CX43 expression is important for reprogramming and may mediate the MET that is associated with the acquisition of pluripotency.
Collapse
Affiliation(s)
- Qiong Ke
- Center for Stem Cell Biology and Tissue Engineering, Key Laboratory for Stem Cells and Tissue Engineering, Ministry of Education
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Bax NAM, Pijnappels DA, van Oorschot AAM, Winter EM, de Vries AAF, van Tuyn J, Braun J, Maas S, Schalij MJ, Atsma DE, Goumans MJ, Gittenberger-de Groot AC. Epithelial-to-mesenchymal transformation alters electrical conductivity of human epicardial cells. J Cell Mol Med 2012; 15:2675-83. [PMID: 21251220 PMCID: PMC4373436 DOI: 10.1111/j.1582-4934.2011.01266.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The myocardium of the developing heart tube is covered by epicardium. These epicardial cells undergo a process of epithelial-to-mesenchymal transformation (EMT) and develop into epicardium-derived cells (EPDCs). The ingrowing EPDCs differentiate into several celltypes of which the cardiac fibroblasts form the main group. Disturbance of EMT of the epicardium leads to serious hypoplasia of the myocardium, abnormal coronary artery differentiation and Purkinje fibre paucity. Interestingly, the electrophysiological properties of epicardial cells and whether EMT influences electrical conductivity of epicardial cells is not yet known. We studied the electrophysiological aspects of epicardial cells before and after EMT in a dedicated in vitro model, using micro-electrode arrays to investigate electrical conduction across epicardial cells. Therefore, human adult epicardial cells were placed between two neonatal rat cardiomyocyte populations. Before EMT the epicardial cells have a cobblestone (epithelium-like) phenotype that was confirmed by staining for the cell-adhesion molecule β-catenin. After spontaneous EMT in vitro the EPDCs acquired a spindle-shaped morphology confirmed by vimentin staining. When comparing both types we observed that the electrical conduction is influenced by EMT, resulting in significantly reduced conductivity of spindle-shaped EPDCs, associated with a conduction block. Furthermore, the expression of both gap junction (connexins 40, Cx43 and Cx45) and ion channel proteins (SCN5a, CACNA1C and Kir2.1) was down-regulated after EMT. This study shows for the first time the conduction differences between epicardial cells before and after EMT. These differences may be of relevance for the role of EPDCs in cardiac development, and in EMT-related cardiac dysfunction.
Collapse
Affiliation(s)
- Noortje A M Bax
- Department of Anatomy and Embryology, Leiden University Medical Center, Leiden, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Lee CC, Chen WS, Chen CC, Chen LL, Lin YS, Fan CS, Huang TS. TCF12 protein functions as transcriptional repressor of E-cadherin, and its overexpression is correlated with metastasis of colorectal cancer. J Biol Chem 2011; 287:2798-809. [PMID: 22130667 DOI: 10.1074/jbc.m111.258947] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
A correlation of TCF12 mRNA overexpression with colorectal cancer (CRC) metastasis was suggested by microarray data and validated by the survey of 120 patients. Thirty-three (27.5%) of the 120 patients showed tumor TCF12 mRNA overexpression and had a higher rate of metastatic occurrence (p = 0.020) and a poorer survival outcome (p = 0.014). Abundant TCF12 levels were also observed in human CRC cell lines such as SW620 and LoVo, but a relatively low level was detected in SW480 cells. Knockdown of TCF12 expression in SW620 and LoVo cells drastically reduced their activities of migration, invasion, and metastasis. Tight cell-cell contact and an increase in E-cadherin but a concomitant decrease in fibronectin were observed in TCF12-knockdown cells. Connexin 26, connexin 43, and gap-junction activity were also increased upon TCF12-knockdown. In contrast, ectopic TCF12 overexpression in SW480 cells facilitated fibronectin expression and cell migration and invasion activities but diminished cellular levels of E-cadherin, connexin 26, connexin 43, and gap junction. A physical association of TCF12 with the E-cadherin promoter was evidenced by chromatin immunoprecipitation assay. TCF12 was tightly correlated with cellular expression of Bmi1 and EZH2 and was co-immunoprecipitable with Bmi1 and EZH2, suggesting that TCF12 transcriptionally suppressed E-cadherin expression via polycomb group-repressive complexes. Clinically, TCF12 mRNA overexpression was also correlated with E-cadherin mRNA down-regulation in the tumor tissues of our 120 patients (p = 0.013). These studies suggested that TCF12 functioned as a transcriptional repressor of E-cadherin and its overexpression was significantly correlated with the occurrence of CRC metastasis.
Collapse
Affiliation(s)
- Chun-Chung Lee
- National Institute of Cancer Research, National Health Research Institutes, Miaoli 350, Taiwan
| | | | | | | | | | | | | |
Collapse
|
16
|
Jose PA, Chen S, Armando I. Connections in chronic kidney disease: connexin 43 and connexin 37 interaction. Am J Physiol Renal Physiol 2011; 301:F21-3. [PMID: 21525135 PMCID: PMC3129881 DOI: 10.1152/ajprenal.00204.2011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
|
17
|
Micalizzi DS, Farabaugh SM, Ford HL. Epithelial-mesenchymal transition in cancer: parallels between normal development and tumor progression. J Mammary Gland Biol Neoplasia 2010; 15:117-34. [PMID: 20490631 PMCID: PMC2886089 DOI: 10.1007/s10911-010-9178-9] [Citation(s) in RCA: 721] [Impact Index Per Article: 51.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 04/26/2010] [Indexed: 02/07/2023] Open
Abstract
From the earliest stages of embryonic development, cells of epithelial and mesenchymal origin contribute to the structure and function of developing organs. However, these phenotypes are not always permanent, and instead, under the appropriate conditions, epithelial and mesenchymal cells convert between these two phenotypes. These processes, termed Epithelial-Mesenchymal Transition (EMT), or the reverse Mesenchymal-Epithelial Transition (MET), are required for complex body patterning and morphogenesis. In addition, epithelial plasticity and the acquisition of invasive properties without the full commitment to a mesenchymal phenotype are critical in development, particularly during branching morphogenesis in the mammary gland. Recent work in cancer has identified an analogous plasticity of cellular phenotypes whereby epithelial cancer cells acquire mesenchymal features that permit escape from the primary tumor. Because local invasion is thought to be a necessary first step in metastatic dissemination, EMT and epithelial plasticity are hypothesized to contribute to tumor progression. Similarities between developmental and oncogenic EMT have led to the identification of common contributing pathways, suggesting that the reactivation of developmental pathways in breast and other cancers contributes to tumor progression. For example, developmental EMT regulators including Snail/Slug, Twist, Six1, and Cripto, along with developmental signaling pathways including TGF-beta and Wnt/beta-catenin, are misexpressed in breast cancer and correlate with poor clinical outcomes. This review focuses on the parallels between epithelial plasticity/EMT in the mammary gland and other organs during development, and on a selection of developmental EMT regulators that are misexpressed specifically during breast cancer.
Collapse
Affiliation(s)
- Douglas S. Micalizzi
- Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO 80045 USA
- Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, CO 80045 USA
| | - Susan M. Farabaugh
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045 USA
| | - Heide L. Ford
- Department of Obstetrics and Gynecology, University of Colorado School of Medicine, Aurora, CO 80045 USA
- Medical Scientist Training Program, University of Colorado School of Medicine, Aurora, CO 80045 USA
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045 USA
- Program in Molecular Biology, University of Colorado School of Medicine, Aurora, CO 80045 USA
- University of Colorado at Denver, Anschutz Medical Campus, RC1 North, Rm. 5102, Aurora, CO 80045 USA
| |
Collapse
|
18
|
Micalizzi DS, Ford HL. Epithelial-mesenchymal transition in development and cancer. Future Oncol 2010; 5:1129-43. [PMID: 19852726 DOI: 10.2217/fon.09.94] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The epithelial-mesenchymal transition (EMT) is a critical developmental process from the earliest events of embryogenesis to later morphogenesis and organ formation. EMT contributes to the complex architecture of the embryo by permitting the progression of embryogenesis from a simple single-cell layer epithelium to a complex three-dimensional organism composed of both epithelial and mesenchymal cells. However, in most tissues EMT is a developmentally restricted process and fully differentiated epithelia typically maintain their epithelial phenotype. Recently, elements of EMT, specifically the loss of epithelial markers and the gain of mesenchymal markers, have been observed in pathological states, including epithelial cancers. Analysis of the molecular mechanisms of this oncogenic epithelial plasticity have implicated the inappropriate expression and activation of developmental EMT programs, suggesting that cancer cells may reinstitute properties of developmental EMT including enhanced migration and invasion. Thus, in the context of cancer, an EMT-like process may permit dissemination of tumor cells from the primary tumor into the surrounding stroma, setting the stage for metastatic spread. Consistent with this hypothesis, activation of these developmental EMT programs in human cancer correlates with advanced disease and poor prognosis. This review will focus on the current knowledge regarding developmental EMT pathways that have been implicated in cancer progression.
Collapse
Affiliation(s)
- Douglas S Micalizzi
- Program in Molecular Biology, Medical Scientist Training Program, University of Colorado School of Medicine, Aurora CO 80045, USA
| | | |
Collapse
|
19
|
Lim MCC, Maubach G, Zhuo L. TGF-beta1 down-regulates connexin 43 expression and gap junction intercellular communication in rat hepatic stellate cells. Eur J Cell Biol 2009; 88:719-30. [PMID: 19781809 DOI: 10.1016/j.ejcb.2009.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 08/11/2009] [Accepted: 08/11/2009] [Indexed: 12/27/2022] Open
Abstract
Intercellular communication is an important tool used by the cells to effectively regulate concerted responses. Hepatic stellate cells (HSCs) communicate to each other through functional gap junctions composed of connexin 43 (Cx43) proteins. We show that exogenous human TGF-beta1 (hTGF-beta1), a pro-fibrotic stimulus, decreases Cx43 mRNA and protein in a rat HSC cell line and primary HSCs. Furthermore, hTGF-beta1 increases the phosphorylation of Cx43 at serine 368. These effects lead to a decrease in the gap junction intercellular communication between the HSCs, as shown by gap-FRAP analysis. We also observe the binding of Snai1, from the nuclear extract of HSCs, to a Snai1 consensus sequence in the Cx43 promoter. In the same context, Snai1 siRNA transfection results in an up-regulation of Cx43 suggesting that TGF-beta1 may regulate Cx43 via Snai1. In addition, we demonstrate that the knockdown of Cx43 by siRNA transfection results in a slower proliferation of HSCs. These findings illuminate a new effect of TGF-beta1 in HSCs, namely the regulation of intercellular communication by affecting the expression level and the phosphorylation state of Cx43 through Snai1 signaling.
Collapse
Affiliation(s)
- Michelle Chin Chia Lim
- Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos, #04-01, Singapore 138669, Singapore
| | | | | |
Collapse
|
20
|
Johnson LN, Koval M. Cross-talk between pulmonary injury, oxidant stress, and gap junctional communication. Antioxid Redox Signal 2009; 11:355-67. [PMID: 18816185 PMCID: PMC2933150 DOI: 10.1089/ars.2008.2183] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Gap junction channels interconnect several different types of cells in the lung, ranging from the alveolar epithelium to the pulmonary vasculature, each of which expresses a unique subset of gap junction proteins (connexins). Major lung functions regulated by gap junctional communication include coordination of ciliary beat frequency and inflammation. Gap junctions help enable the alveolus to regulate surfactant secretion as an integrated system, in which type I cells act as mechanical sensors that transmit calcium transients to type II cells. Thus, disruption of epithelial gap junctional communication, particularly during acute lung injury, can interfere with these processes and increase the severity of injury. Consistent with this, connexin expression is altered during lung injury, and connexin-deficiency has a negative impact on the injury response and lung-growth control. It has recently been shown that alcohol abuse is a significant risk factor associated with acute respiratory distress syndrome. Oxidant stress and hormone-signaling cascades in the lung induced by prolonged alcohol ingestion are discussed, as well as the effects of these pathways on connexin expression and function.
Collapse
Affiliation(s)
- Latoya N Johnson
- Division of Pulmonary, Allergy and Critical Care Medicine, and Emory Alcohol and Lung Biology Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA
| | | |
Collapse
|
21
|
Schnaper HW, Jandeska S, Runyan CE, Hubchak SC, Basu RK, Curley JF, Smith RD, Hayashida T. TGF-beta signal transduction in chronic kidney disease. Front Biosci (Landmark Ed) 2009; 14:2448-65. [PMID: 19273211 DOI: 10.2741/3389] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Transforming growth factor (TGF)-beta is a central stimulus of the events leading to chronic progressive kidney disease, having been implicated in the regulation of cell proliferation, hypertrophy, apoptosis and fibrogenesis. The fact that it mediates these varied events suggests that multiple mechanisms play a role in determining the outcome of TGF-beta signaling. Regulation begins with the availability and activation of TGF-beta and continues through receptor expression and localization, control of the TGF-beta family-specific Smad signaling proteins, and interaction of the Smads with multiple signaling pathways extending into the nucleus. Studies of these mechanisms in kidney cells and in whole-animal experimental models, reviewed here, are beginning to provide insight into the role of TGF-beta in the pathogenesis of renal dysfunction and its potential treatment.
Collapse
Affiliation(s)
- H William Schnaper
- Division of Kidney Diseases, Department of Pediatrics, Northwestern University Feinberg School of Medicine, 303 E Chicago Ave.; Chicago, IL 60611-3008, USA.
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Bierhuizen MFA, Boulaksil M, van Stuijvenberg L, van der Nagel R, Jansen AT, Mutsaers NAM, Yildirim C, van Veen TAB, de Windt LJ, Vos MA, van Rijen HVM. In calcineurin-induced cardiac hypertrophy expression of Nav1.5, Cx40 and Cx43 is reduced by different mechanisms. J Mol Cell Cardiol 2008; 45:373-84. [PMID: 18662696 DOI: 10.1016/j.yjmcc.2008.06.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 05/28/2008] [Accepted: 06/27/2008] [Indexed: 11/28/2022]
Abstract
Alterations in expression levels of Na(v)1.5, Cx43 and Cx40 have been frequently reported in cardiac disease and are associated with the development of arrhythmias, but little is known about the underlying molecular mechanisms. In this study we investigated electrical conduction and expression of Na(v)1.5, Cx43 and Cx40 in hearts of transgenic mice overexpressing a constitutively active form of calcineurin (MHC-CnA). ECG recordings showed that atrial, atrioventricular and ventricular activation were significantly prolonged in MHC-CnA hearts as compared to wildtype (WT) littermates. Epicardial activation and arrhythmia susceptibility analysis revealed increased ventricular activation thresholds and arrhythmia vulnerability. Moreover, epicardial ventricular activation patterns in MHC-CnA mice were highly discontinuous with multiple areas of block. These impaired conduction properties were associated with severe reductions in Na(v)1.5, Cx43 and Cx40 protein expression in MHC-CnA hearts as visualized by immunohistochemistry and immunoblotting. Real-time RT-PCR demonstrated that the decreased protein levels for Na(v)1.5 and Cx40, but not for Cx43, were accompanied by corresponding reductions at the RNA level. Cx43 RNA isoform analysis indicated that the reduction in Cx43 protein expression is caused by a post-transcriptional mechanism rather than by RNA isoform switching. In contrast, RNA isoform analysis for Cx40 and Na(v)1.5 provided additional evidence that in calcineurin-induced hypertrophy the downregulation of these proteins originates at the transcriptional level. These results provide the molecular rationale for Na(v)1.5, Cx43 and Cx40 downregulation in this model of hypertrophy and failure and the development of the pro-arrhythmic substrate.
Collapse
Affiliation(s)
- Marti F A Bierhuizen
- Department of Medical Physiology, Division Heart & Lungs, University Medical Center Utrecht, Yalelaan 50, 3584 CM Utrecht, The Netherlands.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Sauka-Spengler T, Bronner-Fraser M. A gene regulatory network orchestrates neural crest formation. Nat Rev Mol Cell Biol 2008; 9:557-68. [PMID: 18523435 DOI: 10.1038/nrm2428] [Citation(s) in RCA: 529] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The neural crest is a multipotent, migratory cell population that is unique to vertebrate embryos and gives rise to many derivatives, ranging from the peripheral nervous system to the craniofacial skeleton and pigment cells. A multimodule gene regulatory network mediates the complex process of neural crest formation, which involves the early induction and maintenance of the precursor pool, emigration of the neural crest progenitors from the neural tube via an epithelial to mesenchymal transition, migration of progenitor cells along distinct pathways and overt differentiation into diverse cell types. Here, we review our current understanding of these processes and discuss the molecular players that are involved in the neural crest gene regulatory network.
Collapse
Affiliation(s)
- Tatjana Sauka-Spengler
- Division of Biology 13974, California Institute of Technology, Pasadena, California 91125, USA.
| | | |
Collapse
|
24
|
The LIM protein AJUBA recruits protein arginine methyltransferase 5 to mediate SNAIL-dependent transcriptional repression. Mol Cell Biol 2008; 28:3198-207. [PMID: 18347060 DOI: 10.1128/mcb.01435-07] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The SNAIL transcription factor contains C-terminal tandem zinc finger motifs and an N-terminal SNAG repression domain. The members of the SNAIL family have recently emerged as major contributors to the processes of development and metastasis via the regulation of epithelial-mesenchymal transition events during embryonic development and tumor progression. However, the mechanisms by which SNAIL represses gene expression are largely undefined. Previously we demonstrated that the AJUBA family of LIM proteins function as corepressors for SNAIL and, as such, may serve as a platform for the assembly of chromatin-modifying factors. Here, we describe the identification of the protein arginine methyltransferase 5 (PRMT5) as an effector recruited to SNAIL through an interaction with AJUBA that functions to repress the SNAIL target gene, E-cadherin. PRMT5 binds to the non-LIM region of AJUBA and is translocated into the nucleus in a SNAIL- and AJUBA-dependent manner. The depletion of PRMT5 in p19 cells stimulates E-cadherin expression, and the SNAIL, AJUBA, and PRMT5 ternary complex can be found at the proximal promoter region of the E-cadherin gene, concomitant with increased arginine methylation of histones at the locus. Together, these data suggest that PRMT5 is an effector of SNAIL-dependent gene repression.
Collapse
|
25
|
Moesin signalling induces F9 teratocarcinoma cells to differentiate into primitive extraembryonic endoderm. Cell Signal 2008; 20:163-75. [DOI: 10.1016/j.cellsig.2007.10.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Revised: 08/24/2007] [Accepted: 10/03/2007] [Indexed: 11/18/2022]
|
26
|
Krawetz R, Kelly GM. Wnt6 induces the specification and epithelialization of F9 embryonal carcinoma cells to primitive endoderm. Cell Signal 2007; 20:506-17. [PMID: 18160257 DOI: 10.1016/j.cellsig.2007.11.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 10/31/2007] [Accepted: 11/01/2007] [Indexed: 12/25/2022]
Abstract
Epithelial-to-mesenchymal transitions (EMTs) play key roles in the normal development of an organism as well as its demise following the metastasis of a malignant tumour. An EMT during early mouse development results in the differentiation of primitive endoderm into the parietal endoderm that forms part of the parietal yolk sac. In the embryo, primitive endoderm develops from cells in the inner cell mass, but the signals that instruct these cells to become specified and adopt an epithelial fate are poorly understood. The mouse F9 teratocarcinoma cell line, a model that can recapitulate the in vivo primitive to parietal endoderm EMT, has been used extensively to elucidate the signalling cascades involved in extraembryonic endoderm differentiation. Here, we identified Wnt6 as a gene up-regulated in F9 cells in response to RA and show that Wnt6 expressing cells or cells exposed to Wnt6 conditioned media form primitive endoderm. Wnt6 induction of primitive endoderm is accompanied by beta-catenin and Snail1 translocation to the nucleus and the appearance of cytokeratin intermediate filaments. Attenuating glycogen synthase kinase 3 activity using LiCl gave similar results, but the fact that cells de-differentiate when LiCl is removed reveals that other signalling pathways are required to maintain cells as primitive endoderm. Finally, Wnt6-induced primitive endodermal cells were tested to determine their competency to complete the EMT and differentiate into parietal endoderm. Towards that end, results show that up-regulating protein kinase A activity is sufficient to induce markers of parietal endoderm. Together, these findings indicate that undifferentiated F9 cells are responsive to canonical Wnt signalling, which negatively regulates glycogen synthase kinase 3 activity leading to the epithelialization and specification of primitive endoderm competent to receive additional signals required for EMT. Considering the ability of F9 cells to mimic an in vivo EMT, the identification of this Wnt6-beta-catenin-Snail signalling cascade has broad implications for understanding EMT mechanisms in embryogenesis and metastasis.
Collapse
Affiliation(s)
- Roman Krawetz
- Department of Biology, Molecular Genetics Unit, University of Western Ontario, London, Ontario, Canada
| | | |
Collapse
|