Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Tokyo, Japan.
Biochem Biophys Res Commun. 2018 Sep 18;503(4):3023-3030. doi: 10.1016/j.bbrc.2018.08.088. Epub 2018 Aug 23.
We found that the Zhx2 gene (whose product is known to act as a tumor suppressor in hepatocellular carcinoma) is expressed in embryonic retinal progenitors and in developing cone bipolar cells in the postnatal retina, as well as in Müller glia in the mature retina. To examine the functions of Zhx2 protein during retinal development, we performed loss- and gain-of-function analyses using a retinal explant culture system. We introduced a plasmid encoding Zhx2 shRNA into isolated mouse retinas at E17.5, and the retinas were cultured as explants. After 3 days of culture, proliferation was slightly enhanced, leading to retinas thicker than in the control, but this phenomenon was observed only transiently. After 14 days of the culture, the thickness and gross morphology of retinas expressing sh-Zhx2 were indistinguishable from those of the control. The numbers of rod cells, amacrine cells, and Müller glia were the same in both groups. However, although the total number of bipolar cells was the same, the experimental group saw an increased population of ON bipolar cells, and decreased numbers of a subset of OFF bipolar cells. We also examined the effects of overexpression of Zhx2. Although Zhx2 acts as a tumor suppressor, its overexpression in developing retinas did not lead to any discernible difference in retinal thickness, suggesting that proliferation activity was not affected. After 14 days of explant culture, the total number of bipolar cells decreased, and subset composition was altered. Taken together, these results suggest that Zhx2 plays roles in the regulation of bipolar cell subset fate determination during retinal development.
我们发现，Zhx2 基因（其产物已知在肝细胞癌中作为肿瘤抑制因子发挥作用）在胚胎视网膜祖细胞和出生后视网膜的发育性锥体双极细胞中表达，以及在成熟视网膜的 Müller 胶质细胞中表达。为了研究 Zhx2 蛋白在视网膜发育过程中的功能，我们使用视网膜离体培养系统进行了失活和功能获得分析。我们在 E17.5 将编码 Zhx2 shRNA 的质粒引入分离的小鼠视网膜中，并将视网膜作为离体培养物进行培养。培养 3 天后，增殖略有增强，导致视网膜比对照更厚，但这种现象仅短暂出现。培养 14 天后，表达 sh-Zhx2 的视网膜的厚度和大体形态与对照无区别。两组的杆状细胞、无长突细胞和 Müller 胶质细胞数量相同。然而，尽管双极细胞的总数相同，但实验组的 ON 双极细胞数量增加，而一部分 OFF 双极细胞数量减少。我们还检查了过表达 Zhx2 的影响。尽管 Zhx2 作为肿瘤抑制因子发挥作用，但它在发育中的视网膜中的过表达并没有导致视网膜厚度出现任何明显差异，表明增殖活性没有受到影响。在离体培养 14 天后，双极细胞的总数减少，并且亚群组成发生改变。总之，这些结果表明，Zhx2 在视网膜发育过程中调节双极细胞亚群命运决定中发挥作用。
