Fristrom D, Wilcox M, Fristrom J
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Development. 1993 Feb;117(2):509-23. doi: 10.1242/dev.117.2.509.
We first summarize wing development during metamorphosis of Drosophila and identify four critical steps in the conversion of a folded single layered wing disc to a flat bilayered wing. Each step occurs twice, once during the 12 hour prepupal period and again during the 84 hour pupal period. (1) Apposition in which basal surfaces of dorsal and ventral epithelia come close together. (2) Adhesion in which basal junctions form between the apposed basal surfaces. (3) Expansion in which wing area increases as a result of cells flattening. (4) Separation in which dorsal and ventral epithelia are separated by a bulky extracellular matrix but remain connected by slender cytoplasmic processes containing the microtubules and microfilaments of the transalar cytoskeleton. Disc ultrastructure is correlated with the distribution of the beta chain of integrin, laminin A, and filamentous actin for each key stage of pupal development. Integrin and laminin exhibit a mutually exclusive distribution from the adhesion stage onwards. Integrin is present on the basal surface of intervein cells but not on vein cells whereas laminin A is absent from the basal surfaces of intervein cells but is present on vein cells. We conclude that laminin is not a ligand for integrin in this context. During apposition and adhesion stages integrin is broadly distributed over the basal and lateral surfaces of intervein cells but subsequently becomes localized to small basal foci. These foci correspond to basal contact zones between transalar processes. The distribution of filamentous actin is dynamic, changing from an apical distribution during hair morphogenesis to a basal distribution as the transalar cytoskeleton develops. Basal adherens-type junctions are first evident during the adhesion stage and become closely associated with the transalar cytoskeleton during the separation stage. Thus, basal junction formation occurs in two discrete steps; intercellular connections are established first and junction/cytoskeletal connections are formed about 20 hours later. These observations provide a basis for future investigations of integrin mediated adhesion in vivo.
我们首先总结果蝇变态发育过程中的翅发育情况，并确定将折叠的单层翅盘转变为扁平的双层翅的四个关键步骤。每个步骤发生两次，一次在化蛹前12小时期间，另一次在化蛹84小时期间。（1）贴合，即背侧和腹侧上皮的基底面彼此靠近。（2）黏附，即贴合的基底面之间形成基底连接。（3）扩展，即由于细胞扁平化翅面积增加。（4）分离，即背侧和腹侧上皮被大量细胞外基质分隔，但仍通过含有跨翅细胞骨架的微管和微丝的细长细胞质突起相连。在蛹发育的每个关键阶段，翅盘超微结构与整合素β链、层粘连蛋白A和丝状肌动蛋白的分布相关。从黏附阶段开始，整合素和层粘连蛋白呈现相互排斥的分布。整合素存在于翅脉间细胞的基底面而非翅脉细胞上，而层粘连蛋白A在翅脉间细胞的基底面不存在但在翅脉细胞上存在。我们得出结论，在这种情况下层粘连蛋白不是整合素的配体。在贴合和黏附阶段，整合素广泛分布于翅脉间细胞的基底面和侧面，但随后定位到小的基底灶。这些灶对应于跨翅突起之间的基底接触区。丝状肌动蛋白的分布是动态的，从毛发生成期间的顶端分布变为随着跨翅细胞骨架发育的基底分布。基底黏着连接在黏附阶段首次明显，并在分离阶段与跨翅细胞骨架紧密相关。因此，基底连接形成分两个离散步骤；细胞间连接首先建立，约20小时后形成连接/细胞骨架连接。这些观察结果为未来体内整合素介导的黏附研究提供了基础。
