Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Invest Ophthalmol Vis Sci. 2011 Sep 21;52(10):7332-9. doi: 10.1167/iovs.11-7724.
Lim2 (MP20) is the second most abundant integral protein of lens fiber cell membranes. A comparative analysis was performed of wild-type and Lim2-deficient (Lim2(Gt/Gt)) mouse lenses, to better define the anatomic and physiologic roles of Lim2.
Scanning electron microscopy (SEM) and confocal microscopy were used to assess the contribution of Lim2 to lens tissue architecture. Differentiation-dependent changes in cytoskeletal composition were identified by mass spectrometry and immunoblot analysis. The effects on cell-cell communication were quantified using impedance analysis.
Lim2-null lenses were grossly normal. At the cellular level, however, subtle structural alterations were evident. Confocal microscopy and SEM analysis revealed that cortical Lim2(Gt/Gt) fiber cells lacked the undulating morphology that characterized wild-type fiber cells. On SDS-PAGE analysis the composition of cortical fiber cells from wild-type and Lim2-null lenses appeared similar. However, marked disparities were evident in samples prepared from the lens core of the two genotypes. Several cytoskeletal proteins that were abundant in wild-type core fiber cells were diminished in the cores of Lim2(Gt/Gt) lenses. Electrophysiological measurements indicated a small decrease in the membrane potential of Lim2(Gt/Gt) lenses and a two-fold increase in the effective intracellular resistivity. In the lens core, this may have reflected decreased expression levels of the gap junction protein connexin 46 (Cx46). In contrast, increased resistivity in the outer cell layers of Lim2(Gt/Gt) lenses could not be attributed to decreased connexin expression and may reflect the absence of cell fusions in Lim2(Gt/Gt) lenses.
Comparative analysis of wild-type and Lim2-deficient lenses has implicated Lim2 in maintenance of cytoskeletal integrity, cell morphology, and intercellular communication.
Lim2（MP20）是晶状体纤维细胞膜中第二丰富的完整蛋白。对野生型和 Lim2 缺陷型（Lim2（Gt/Gt））小鼠晶状体进行了比较分析，以更好地定义 Lim2 的解剖和生理作用。
使用扫描电子显微镜（SEM）和共聚焦显微镜评估 Lim2 对晶状体组织结构的贡献。通过质谱分析和免疫印迹分析鉴定细胞骨架组成的分化依赖性变化。使用阻抗分析量化对细胞间通讯的影响。
Lim2 缺失的晶状体大体上正常。然而，在细胞水平上，存在微妙的结构改变。共聚焦显微镜和 SEM 分析显示，皮质 Lim2（Gt/Gt）纤维细胞缺乏特征为野生型纤维细胞的波浪形形态。在 SDS-PAGE 分析中，野生型和 Lim2 缺失型晶状体的皮质纤维细胞组成似乎相似。然而，在两种基因型的晶状体核心样本中，明显存在差异。在野生型核心纤维细胞中丰富的几种细胞骨架蛋白在 Lim2（Gt/Gt）晶状体的核心中减少。电生理测量表明 Lim2（Gt/Gt）晶状体的膜电位略有降低，有效细胞内电阻增加了两倍。在晶状体核心中，这可能反映了间隙连接蛋白 connexin 46（Cx46）的表达水平降低。相比之下，Lim2（Gt/Gt）晶状体外层细胞层电阻的增加不能归因于连接蛋白表达的降低，并且可能反映了 Lim2（Gt/Gt）晶状体中细胞融合的缺失。
对野生型和 Lim2 缺陷型晶状体的比较分析表明，Lim2 参与维持细胞骨架完整性、细胞形态和细胞间通讯。
