Annexin 8 and differentiation of the retinal pigment epithelium

这项研究有两个广泛的目标。一个是更多地了解一种名为膜联蛋白A8的蛋白质的功能，另一个是了解这种蛋白质如何影响视力。膜联蛋白A8仅在少数细胞类型中表达，并且在肺的气道内衬的细胞中最丰富。这些被称为上皮细胞，并且膜联蛋白A8也在身体其他部位的上皮细胞中表达，包括乳房和眼睛。一个一致的观察结果是，膜联蛋白A8是目前在高水平的上皮细胞是成熟的和功能正常。上皮细胞的成熟过程需要它们从分裂未成熟细胞发育成一片紧密连接的非分裂细胞。随着这一成熟过程的发生，膜联蛋白A8水平稳步增加。有趣的是，膜联蛋白A8水平在癌性上皮细胞中要低得多，最明显的是在乳腺癌中，并且膜联蛋白A8从这些细胞中的消失似乎与成熟过程的逆转有关。这些观察结果使我们假设膜联蛋白A8在某种程度上是上皮细胞成熟和维持成熟上皮片层的正常特征所必需的。支持我们的假设出乎意料地来自一项研究，在这项研究中，我们调查了眼睛上皮细胞的生长和成熟。视网膜是眼睛的一部分，它捕获光线并使我们能够看到，在视网膜中有一层至关重要的上皮细胞，对视网膜健康至关重要。如果没有这些细胞，邻近的光敏感光细胞会迅速死亡（这就是年龄相关性黄斑疾病的情况）。当细胞经历药物诱导的反向成熟过程时，我们检查了所有已知基因的表达，我们发现当这种情况发生时，膜联蛋白A8水平大幅降低。我们还发现，通过迫使细胞表达膜联蛋白A8，我们可以阻止逆成熟。在这里，我们计划使用这些来自眼睛的上皮细胞来研究膜联蛋白A8的功能，以了解它如何保持成熟的上皮状态，以及为什么它需要关闭或抑制成熟以逆转。我们可以使用培养的细胞来完成一些工作，但我们现在也有必要的小鼠品系来研究体内的这一过程。我们已经开发出一种删除视网膜上皮细胞中基因的方法，并将使用这种方法删除活体眼睛中的膜联蛋白A8。然后，我们可以研究这对视力的影响，并检查膜联蛋白A8缺失的上皮细胞是否在活体眼睛中经历成熟逆转。如果它们这样做，并因此以类似于它们在培养物中的行为的方式表现，那么它们可能会从上皮细胞转化为神经元。这将是一个了不起的发展壮举，在未来可能为新的治疗方法铺平道路，因为光感受器的损失导致失明。

There are two broad aims to this research. One is to learn more about the function of a protein named annexin A8, and the other is to find out how this protein influences vision. Annexin A8 is only expressed in a few cell types, and is most abundant in the cells that line the airways of the lungs. These are termed epithelial cells, and annexin A8 is also expressed in epithelial cells in other parts of the body including the breast and eye. A consistent observation is that annexin A8 is present at high levels in epithelial cells that are mature and functioning normally. The maturation process for epithelial cells requires their development from dividing immature cells into a sheet of tightly connected non-dividing cells. As this maturation process occurs, annexin A8 levels steadily increase. Interestingly, annexin A8 levels are much lower in cancerous epithelial cells, most notably in breast cancer, and the disappearance of annexin A8 from these cells seems to be associated with a reversal of the maturation process. These observations led us to the hypothesis that annexin A8 is somehow required for epithelial cell maturation and for maintenance of the normal characteristics of the mature epithelial sheet. Support for our hypothesis came unexpectedly from a study in which we were investigating the growth and maturation of epithelial cells from the eye. In the retina, which is the part of the eye that captures light and enables us to see, there is a layer of vitally important epithelial cells that is essential for retinal health. Without these cells the neighbouring light-sensitive photoreceptors rapidly die (which is what happens in age-related macular disease). We examined the expression of all known genes when the cells underwent a drug-induced reverse-maturation process, and we found that annexin A8 levels were massively reduced when this occurred. We also found that by forcing the cells to express annexin A8, we could prevent the reverse-maturation. Here, we plan to use these epithelial cells from the eye to investigate the function of annexin A8, to find out how it maintains the mature epithelial state, and why it needs to be switched off or suppressed for maturation to reverse. Some of this work we can do using cultured cells, but we now also have the necessary strains of mice to investigate this process in vivo. We have developed a way of deleting a gene in the retinal epithelial cells, and will use this approach to delete annexin A8 in the living eye. We can then investigate the consequences of this on vision, and also examine whether or not the annexin A8-depleted epithelial cells undergo maturation reversal in the living eye. If they do, and thus behave in a manner similar to their behaviour in culture, then they may convert from epithelial cells to neurones. This would constitute a remarkable developmental feat, and in the future may pave the way for new treatments for forms of blindness caused by the loss of photoreceptors.