The T-Box Transcription Factor TBX2 Regulates Cell Proliferation in the Retinal Pigment Epithelium

ABSTRACT

Purpose: Vertebrate eye development and function critically depend on the regulation of proliferation of retinal pigment epithelium (RPE) cells. Hence, a thorough analysis of the molecular parameters controlling RPE cell proliferation is crucial for our understanding of the physiology of this cell type both in health and in disease. The T-box transcription factor TBX2 is an important cell cycle regulator in development and oncogenesis, but its specific role in RPE cell proliferation is far from clear. The purpose of the present study is to investigate whether TBX2 plays any role in regulating RPE cell proliferation.

Materials and methods: The expression of TBX2 in RPE cells was analyzed in wildtype mice and ARPE-19 cells by co-staining for RPE-specific markers and cell proliferation. In vitro, the role of TBX2 was studied by manipulating its levels using RNAi and analyzing the effects on DNA synthesis and cell growth and on gene expression at the RNA and protein levels.

Results: Here, we find that TBX2 is expressed in RPE cells both in vivo and in vitro. Specific knockdown of TBX2 in the human RPE cell line ARPE-19 leads to an accumulation of cells at G1. This cell cycle arrest is accompanied by changes in the levels of known cell cycle regulators and, in particular, by an increase in the levels of the tumor-suppressor gene CCAAT/enhancer-binding protein delta (CEBPD). In fact, simultaneous knockdown of both TBX2 and CEBPD interferes with the reduction in cell proliferation brought about by TBX2 reduction alone.

Conclusions: Our results provide novel insights into the regulatory mechanisms of cell proliferation in the RPE and may contribute to our understanding of normal RPE maintenance and its pathology in degenerative and proliferative disorders of the eye.

Keywords:

• CEBPD
• cell proliferation
• retina
• RPE
• T-box transcription factor

Acknowledgments

We thank Dr. Heinz Arnheiter for thoughtful comments and help with editing and Bing Cheng for technical assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Funding

This work was supported by the National Natural Science Foundation of China (81570892, 81600748), the Zhejiang Provincial Natural Science Foundation (LZ12C12001), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 80314001), and the Research Grant of Wenzhou Medical University.

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China (81570892, 81600748), the Zhejiang Provincial Natural Science Foundation (LZ12C12001), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 80314001), and the Research Grant of Wenzhou Medical University.