DNA甲基化在晶状体发育及白内障中的研究进展

表观遗传学是指基因碱基序列在未发生改变的情况下调控基因表达的一门学科,其研究领域主要涉及DNA甲基化、组蛋白修饰和非编码RNA,其中DNA甲基化沉默基因的表达是表观遗传学重要的调控机制.DNA甲基化状态受环境因素的影响,而晶状体发育异常及白内障形成由多种致病因素决定,其中包括环境因素.因此,研究DNA甲基化在晶状体发育及白内障形成过程中的作用机制尤为重要.本文就近年来DNA甲基化在晶状体发育、年龄相关性白内障、并发性白内障、后发性白内障发病机制中的作用进行综述,通过对DNA甲基化在上述眼部疾病及晶状体发育过程中作用机制的认识及研究,有望在白内障临床治疗中开辟新的途径.     

鼠视网膜新生血管发生过程中Twist基因的表达

目的 探讨视网膜新生血管发生过程中Twist基因的表达情况.方法 对照实验研究.将40只新生C57/BL小鼠分为两组:(1)对照组,正常空气环境中饲养;(2)高氧组,在高氧环境中制作小鼠缺氧性视网膜新生血管动物模型.将出生第7天的小鼠放人氧箱,在75%浓度的高氧环境中饲养5 d后,取出氧箱.待出氧箱第12天和第17天(视网膜新生血管发生高峰时间)分别处死小鼠,制作视网膜铺片和切片,观察小鼠视网膜新生血管发生情况.应用免疫组织化学染色检测小鼠视网膜血管内皮细胞(VE)-钙黏蛋白、波形蛋白及Twist基因表达变化情况;提取全视网膜RNA,应用逆转录聚合酶链反应(RT-PCR)法检测VE-钙黏蛋白、波形蛋白及Twist基因表达变化情况.应用SPSS 11.5统计学软件进行数据处理,对高氧组与对照组小鼠出生后不同时间的VE-钙黏蛋白、波形蛋白、Twist基因表达的灰度值比较,采用两因素析因设计的方差分析,以P<0.05作为差异有统计学意义.结果 免疫组织化学检测结果显示,出生后第17天的小鼠,高氧组VE-钙黏蛋白表达的灰度值(65.19±8.39)与对照组(75.36±7.04)相比明显减少(F=8.616,P=0.009),波形蛋白表达的灰度值(95.09±14.13)与对照组(82.14±6.32)相比明显升高(F=6.999,P=0.016),Twist基因表达的灰度值(119.48±7.90)与对照组(93.30±6.37)相比亦明显升高(F=66.557,P=0.000).RT-PCR检测结果显示,不同处理组间波形蛋白、Twist基因表达的灰度值与检查时间存在交互作用(F=5.508,P=0.032;F=17.760,P=0.001).结论 在小鼠视网膜新生血管形成过程中,细胞转型调控的Twist基因发挥着重要作用,其作用机制可能是通过下调血管内皮细胞间的紧密连接蛋白,促进内皮细胞转型实现.     

PAX6基因及其下游促分化基因在视网膜母细胞瘤分化过程中的作用

 目的 检测在视网膜母细胞瘤（retinoblastoma,RB）中,眼发育调控基因PAX6及其下游促分化基因MATH5和BRN3b在蛋白水平的表达情况,从而探讨PAX6基因在RB分化过程中的作用。 设计 病例对照研究。研究对象 新鲜RB组织10例,正常视网膜组织10例。方法  实验组：RB组织;对照组：正常视网膜组织。采用WesternBlot法检测新鲜视网膜母细胞瘤组织和正常视网膜组织中Pax6、Math5、Brn3b蛋白质水平的表达情况并作比较。主要指标 Pax6、Math5、Brn3b蛋白质的表达水平。结果 本研究中RB组织和正常视网膜组织中均可检测出Pax6、Math5、Brn3b蛋白的表达。与正常视网膜组织相比较,RB组织中Pax6、Math5、Brn3b蛋白的表达水平增高（P均<0.001）;Math5与Pax6蛋白表达具有线性相关性（r=0.949, P<0.001）, Brn3b与Math5蛋白表达具有线性相关性（r=0.927, P<0.001）。结论 在RB组织中, PAX6基因上调下游促分化基因MATH5和BRN3b表达水平,促进RB组织的分化。     

应重视表观遗传学与晶状体的相关研究

表观遗传学是传统遗传学的分支之一,目前已成为生物医学中一个日益重要的研究领域,是研究不涉及DNA序列改变,而通过DNA甲基化、组蛋白修饰、非编码RNA,如miRNA等方式对基因表型进行调控并可进行遗传的科学。目前已发现,表观遗传学与生命科学密切相关,在眼科学领域,表观遗传与各种眼组织的生理活动和疾病发生均有关联。由于传统遗传学导致的疾病不可逆,而表观遗传是可逆的过程,因此表观遗传与眼科疾病关系的研究正逐渐引起重视。晶状体上皮细胞（LECs）的生长、分化、衰老、上皮一间充质转化（EMT）等均受到表观遗传学的调控,晶状体疾病,如白内障可能与表观遗传学因素有密切关联,大力开展晶状体表观遗传学研究可能为研究白内障的发病机制及防治提供新的思路和方法。目前国内外一些研究者已将表观遗传学方法应用于晶状体生理和病理的研究,国内的眼科医学工作者应关注和跟踪这些新的研究动态和前沿,并积极参与其中。     

Changes in three types of ubiquitin mRNA and ubiquitin-protein conjugate levels during lens development

Ubiquitin is a small, highly conserved protein that covalently attaches to other proteins to form a unique branched protein structure. The best characterized function of this post-translational modification is to mark the modified protein for degradation by the proteasome. To investigate whether ubiquitin genes are regulated in lens development, the authors analyzed the levels of three ubiquitin mRNAs (UbA(52), UbB and UbC) in freshly dissected fiber and epithelial cells, and in epithelial explants induced to differentiate ex vivo. Explants, comprising the capsule and adherent epithelial cells, were dissected from lenses of 3 day old Sprague Dawley rats and cultured +/-bFGF to induce differentiation. Quantitative competitive RT-PCR was used to determine the mRNA levels in fresh and cultured cells. UbA(52), UbB and UbC mRNAs were 3.2 (P < 0.0001), 5.0 (P < 0.0001) and 6.8 (P < 0.0001) fold higher, respectively, in freshly dissected epithelial cells than in differentiated fiber cells. Immunological spot assays showed that ubiquitin protein is over two fold as high in rat pup lens epithelial cells as in fiber cells. The ubiquitin protein in fiber cells of adult rat is lower than that in adult epithelium and in pup fiber cells, indicating that ubiquitin content further decreased during lens fiber maturation. Western blots showed a greater amount of protein-conjugated ubiquitin (MW > 81 kD) in epithelial cells than in fiber cells, demonstrating a parallel pattern between the expression of ubiquitin mRNA, the level of ubiquitin protein and the level of conjugates in the cells. Epithelial cell explant cultures permit study of cells initiating differentiation. In contrast to fully differentiated fiber cells, explant cultures induced to initiate differentiation underwent differential up-regulation of ubiquitin gene expression. UbA(52) and UbB mRNA levels in +bFGF (differentiating) explant cultures were 2.6 (P < 0.001) and 1.4 (P < 0.001) fold higher, respectively, than those of -bFGF cultures. UbC mRNA content was similar in explants cultured with or without bFGF. Dissection of the isolated epithelial cells into regions representing distinct populations gave results consistent with this observation of the explant results. UbA(52), UbB and UbC mRNAs are 2.0, 2.2 and 1.76 fold higher, respectively, in the peripheral (initiating differentiation) than in the central (undifferentiated) region of epithelial cells. These results together indicate that UbA(52) and UbB mRNAs are transiently increased during the initiation and early stages of differentiation. However, UbC mRNA appears to be relatively unaffected at the earliest stage in this differentiation model and may have a different distribution than UbA(52) and UbB in the anterior lens cells. These data are consistent with an important role for ubiquitin during the early stages of lens differentiation. The selective expression indicates that the three genes have specific differentiation related functions.     

钠尿肽受体A（NPR-A）在小鼠角膜和晶状体发育过程中的表达

目的　检测钠尿肽受体A（natriuretic peptide receptor A,NPR-A）在不同鼠龄小鼠角膜和晶状体内的表达,探讨其在小鼠眼发育过程中的作用。方法　选用C57BL/6转基因小鼠,收集从 E14到P90小鼠眼球标本120只,采用40 g·L^-1多聚甲醛灌注固定后,石蜡包埋切片,采用免疫组织化学方法对NPR-A在角膜和晶状体中的表达进行免疫荧光检测。结果　在E16,NPR-A高表达于角膜上皮细胞中,并持续至成年;其在角膜基质层和内皮细胞的表达也始于E16,而在P14之后,NPR-A表达随鼠龄的增加逐渐减弱。此外,NPR-A在P0小鼠晶状体上皮细胞膜内被检测到,并持续高表达至成年。在E16,由晶状体后壁上皮细胞生成的初级纤维开始高表达NPR-A,但随着鼠龄的增长和纤维结构的改变而逐渐减弱,直到P90消失。结论　NPR-A可能参与了角膜和晶状体生长和发育,并且对维持角膜上皮细胞的增生和修复以及晶状体的通透性具有重要作用。