Cornea Division, Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America.
PLoS One. 2013 Apr 22;8(4):e61833. doi: 10.1371/journal.pone.0061833. Print 2013.
Corneal epithelial stem cells or limbal stem cells (LSCs) are responsible for the maintenance of the corneal epithelium in humans. The exact location of LSCs is still under debate, but the increasing need for identifying the biological processes in the limbus, where LSCs are located, is of great importance in the regulation of LSCs. In our current study we identified 146 preferentially expressed genes in the human limbus in direct comparison to that in the cornea and conjunctiva. The expression of newly identified limbal transcripts endomucin, fibromodulin, paired-like homeodomain 2 (PITX2) and axin-2 were validated using qRT-PCR. Further protein analysis on the newly identified limbal transcripts showed protein localization of PITX2 in the basal and suprabasal layer of the limbal epithelium and very low expression in the cornea and conjunctiva. Two other limbal transcripts, frizzled-7 and tenascin-C, were expressed in the basal epithelial layer of the limbus. Gene ontology and network analysis of the overexpressed limbal genes revealed cell-cell adhesion, Wnt and TGF-β/BMP signaling components among other developmental processes in the limbus. These results could aid in a better understanding of the regulatory elements in the LSC microenvironment.
角膜上皮干细胞或角膜缘干细胞（LSCs）负责维持人类的角膜上皮。LSCs 的确切位置仍存在争议，但确定位于 LSCs 处的角膜缘生物学过程的需求不断增加，对于 LSCs 的调节非常重要。在我们目前的研究中，我们在直接比较角膜和结膜的情况下，确定了 146 个在人角膜缘中优先表达的基因。使用 qRT-PCR 验证了新鉴定的角膜缘转录物内粘蛋白、纤维调蛋白、同源盒蛋白 2（PITX2）和轴突蛋白 2 的表达。对新鉴定的角膜缘转录物的进一步蛋白质分析显示，PITX2 蛋白定位于角膜缘上皮的基底和超基底层，在角膜和结膜中的表达非常低。另外两个角膜缘转录物，卷曲蛋白 7 和腱蛋白 C，在角膜缘的基底上皮层表达。过表达的角膜缘基因的基因本体论和网络分析显示，在角膜缘中存在细胞-细胞黏附、Wnt 和 TGF-β/BMP 信号成分等发育过程。这些结果可能有助于更好地理解 LSC 微环境中的调节元件。
