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November 16, 2016

A master transcription factor for eye cells

CiRA researchers show PAX6 expression is essential for corneal epithelial cells.

The ability of a cell to preserve its identity is crucial for healthy function. When essential transcription factors dysfunction, proper regulation of gene expression is lost, potentially leading to degeneration and disease. Although the cornea is exclusively expressed in the eye, transcription factors that preserve its identity are of high interest, in part because of the success using stem cells to treat related diseases. For example, the first and only transplant of iPS cell-derived tissues in a patient was done to treat age-related macular degeneration. In its latest report, the Shinji Masui lab at CiRA shows that the transcription factor PAX6 is essential for the identity of corneal epithelial cells, which cover the surface of the cornea.

To demonstrate PAX6 necessity, the lab used CRISPR-Cas9 technology to modify PAX6 expression. Cells in which PAX6 was repressed were still corneal epithelial cells, but the cells were larger than normal and the expression of crucial genes associated with this cell identity was also repressed. To compensate, the cells overexpressed genes responsible for other epidermal cells, suggesting that function was compromised. "The function of epithelia depends on the expression of different keratin genes," explained Masui. "We found that by modifying the PAX6 expression, the cells would change their expression of keratin isoforms. These changes probably mean the function of the epithelia changed too."

These findings should have implications beyond the identity of cells in the eye. Epidermal cells like those in the skin have been extraordinarily difficult to prepare from stem cells compared with other cell types. The finding that PAX6 repression stimulates compensatory expression of keratin genes more affiliated with skin epidermis could provide insights on how to prepare these cell types in the lab.

"Our goal is to build a library of transcription factors that determine cell identity," said Masui. "While this study was about corneal epidermal cells, we are interested in understanding the principles stipulating cell identity in general."

Paper Details
  • Journal: Experimental Eye Research

  • Title: PAX6 regulates human corneal epithelium cell identity

  • Authors: Koji Kitazawa1,2,3, Takafusa Hikichi1, Takahiro Nakamura2, Chie Sotozono3, Shigeru Kinoshita2, and Shinji Masui1

  • Author Affiliations:
    1. Center for iPS Cell Research and Application (CiRA), Kyoto University, Kyoto, Japan
    2. Department of Frontier Medical Science and Technology for Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
    3. Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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