This web page was produced as an assignment for Genetics 677, an undergraduate course at UW-Madison.
Overexpression of NANOG in Gestational Trophoblastic Diseases
Summary
In 2008, Siu and her research group from the University of Hong Kong investigated the relation of Nanog to gestational trophoblastic diseases. Two types of gestational trophoblastic diseases were investigated - Hydatidiform mole (HM) and Choriocarcinoma. Siu et al. determined that a higher expression level of Nanog mRNA and protein led to a predisposition for the manifestation of chronic (persistent) gestational trophoblastic diseases.
Through investigations with well characterized Choriocarcinoma cell lines (a type of gestational trophoblastic disease), Siu et al. determined that Nanog has a role in Choriocarcinoma cell death, migration and invasion. These Nanog functions may be the culprits responsible for Gestational Trophoblastic Diseases in pregnant women.
Hypothesis: Nanog expression levels are involved in the manifestation of gestational trophoblastic disease.
Keypoints to learn:
1) Higher Nanog messenger RNA (mRNA) and protein level is observed in the following:
a) Hydatidiform mole (HM) and choriocarcinomic tissues compared to normal first trimester tissues
b) HMs that developed persistent Gestational Trophoblastic Disease compared to regressive HMs
This means that a higher level of Nanog translates into a higher possibility of getting chronic HM.
2) Nanog is has a role in cell death , invasion and migration but not cell proliferation or cell cycle for Choriocarcinomas cells.
The higher level of Nanog found in Choriocarcinoma and HM cells lead to decreased death in these cells, and later resulting in Gestational Trophoblastic disease.
Journal figures
Table 1 and 2 are lists of the primers and antibodies used for the experiment.
Figure 1 and 2: The figures shows that Nanog mRNA and protein level is higher in tissues from Gestational trophoblastic disease patients compared to normal tissues from pregnant women. There is also a higher expression level of Nanog in tissues from chronic Gestational trophoblastic disease patient tissues. Figure 1 demonstrate the comparison of mRNA levels and Figure 2 demonstrates the comparison of protein levels.
Figure 3: The comparison of staining in HM tissues show that an increased level of Nanog decreases the apoptotic protein M30 CytoDeath antibody. Nanog can be deduced to be responsible for decreasing cell death.
Figure 4: In Nanog knockdown Choriocarcinoma lines, increased levels of mRNA and proteins involved in cell death is observed. This suggests that the decreased level of Nanog in Choriocarcinoma lines may be responsible for directing the cells towards cell death.
Figure 5: In similar Choriocarcinoma lines used in Figure 4, the Nanog knockdown lines have a decreased amount of mRNA and proteins that are responsible for cell invasion and migration. This suggest that the lack of Nanog might limit cells from migration and invasion.
My comments:
This above research journal is a focused investigation of the role of Nanog expression level in gestational trophoblastic diseases. It provides a comprehensive look on the possible role and function of Nanog in causing gestational trophoblastic diseases. The paper is relatively concise and clear with the experiments performed, most of which are relevant to illustrating the key points of the study.
For comparative staining experiments, I think that the results would be much more convincing if double staining was performed or an integrated overlap image of the two separate stains are shown to illustrate the relation between Nanog and the other proteins of interest. The use of different tissues resulted in problems of comparing the stains, the number of cells may vary in different sectinos as well. Also the staining pictures did not show especially glaring contrasts, making it hard to come to similar conclusions as the authors.
Also, the knockout experiments did not show a complete removal of Nanog in the qPCR experiments. Perhaps an alternative method of knockdown could be used like morpholinos.
I felt that the study could be even more comprehensive if the following was performed, the mRNA and protein level of Nanog was investigated in HM cell lines or tissues. However, I had problems visualizing the picture from Figure 1E and other figures which have microscopic shots of cells. The resolution of the pictures, especially in black and white, was not helpful. It will be great if someone could direct a better, colored version of the paper to me. Thank you!
Possible future investigations:
- Knockdown experiments were only carried out in Choriocarcinoma cell lines, therefore, function of Nanog in HM cells was not determined.
- Only the expression level of Nanog was investigated in the tissues, and knockdown cell lines. Is Nanog the sole gene regulated? Or is there a cluster of genes affected? Is Nanog a downstream factor of some other component in a signaling pathway that leads to the pathogenesis of gestational trophoblastic disease?
- Nanog is mentioned to have a role in other human neoplasms, like germ cell tumors, breast carcinomas, and osteosarcoma. Perhaps the level of expression and function of Nanog in these cancerous tissues could also be investigated. A comparison of the levels and function of Nanog in these different cancers can be compared to the knowledge we have for Gestational Trophoblastic disease.
| nanog_and_gtd.pdf | |
| File Size: | 460 kb |
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Reference:
Siu, M. K. Y., Wong, E. S. Y., Chan, H. Y., Ngan, H. Y. S.,Chan, K. Y. K., and Cheung, A. N. Y.(2008) Overexpression of NANOG in Gestational Trophoblastic Diseases. The American Journal for Pathology, 173(4), 1165-1172. DOI: 10.2353/ajpath.2008.080288
Ka Yi, Ling ([email protected])
Page last updated 05/13/09
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