Lee J K, Brandin E, Branton D, Goldstein L S
Howard Hughes Medical Institute, Department of Pharmacology, University of California, San Diego, La Jolla 92093-0683, USA.
Development. 1997 Jan;124(2):353-62. doi: 10.1242/dev.124.2.353.
To understand the role of the spectrin-based membrane skeleton in generating epithelial polarity, we characterized the distribution of membrane skeletal components in Drosophila ovarian follicle cells and in somatic clones of mutant cells that lack alpha-spectrin. Immunolocalization data reveal that wild-type follicle cells contain two populations of spectrin heterodimers: a network of alphabeta heterodimers concentrated on the lateral plasma membrane and an alphabetaH population targeted to the apical surface. Induction of somatic clones lacking alpha-spectrin leads to follicle cell hyperplasia. Surprisingly, elimination of alpha-spectrin from follicle cells does not appear to prevent the assembly of conventional beta-spectrin and ankyrin at the lateral domain of the follicle cell plasma membrane. However, the alpha-subunit is essential for the correct localization of betaH-spectrin to the apical surface. As a consequence of disrupting the apical membrane skeleton a distinct sub population of follicle cells undergoes unregulated proliferation which leads to the loss of monolayer organization and disruption of the anterior-posterior axis of the oocyte. These results suggest that the spectrin-based membrane skeleton is required in a developmental pathway that controls follicle cell monolayer integrity and proliferation.
为了理解基于血影蛋白的膜骨架在产生上皮极性中的作用，我们对果蝇卵巢滤泡细胞以及缺乏α - 血影蛋白的突变体细胞的体细胞克隆中膜骨架成分的分布进行了表征。免疫定位数据显示，野生型滤泡细胞含有两种血影蛋白异二聚体群体：一种是集中在外侧质膜上的αβ异二聚体网络，另一种是靶向顶端表面的αβH群体。缺乏α - 血影蛋白的体细胞克隆的诱导导致滤泡细胞增生。令人惊讶的是，从滤泡细胞中消除α - 血影蛋白似乎并未阻止传统β - 血影蛋白和锚蛋白在滤泡细胞质膜外侧结构域的组装。然而，α亚基对于βH - 血影蛋白正确定位到顶端表面至关重要。由于破坏了顶端膜骨架，一个独特的滤泡细胞亚群经历不受调控的增殖，这导致单层组织结构丧失以及卵母细胞前后轴的破坏。这些结果表明，基于血影蛋白的膜骨架在控制滤泡细胞单层完整性和增殖的发育途径中是必需的。
