Brown F, Tirone S, Wolfe J
Biology Dept., Wesleyan University, Middletown, Connecticut 06459.
Dev Dyn. 1993 Mar;196(3):195-204. doi: 10.1002/aja.1001960306.
The relationship between direct cell contacts and subsequent cell-cell adhesion was studied in the ciliated protozoan, Tetrahymena thermophila. During sexual reproduction, adhesion into pairs begins at approximately 1 hr after mixing starved complementary mating types. However, direct contacts between cells prior to pairing are known to be required for the development of adhesion-readiness. We find here that the initial contact interactions are necessary but not sufficient to drive the cells to adhesion-readiness. Secondary interactions are needed. Two distinct experimental strategies were used. First, we examined the effects of a mutant that is unable to pair but which can stimulate two different wild-type mating type cells to pair when mixed. We showed that stimulation by the mutant is only partial; in response to mutant cells, wild-type cells ceased forming food vacuoles but did not undergo tip transformation or concanavalin A (Con A)-receptor tipping. Further, kinetic analysis shows that when mixed together, pair-formation among partially stimulated wild-type cells is slightly delayed, allowing time for these pre-pairing processes to occur. This indicates that, beyond the initial contact interaction, mutant-stimulated wild-type cells require a subsequent interaction which cannot be fulfilled by the mutants. Secondly, we found that by blocking contact interactions between wild-type mating types at various time intervals after they were mixed, additional increase in tip transformation and Con A receptor tipping was prevented. Further, both processes underwent a regression. This indicates that multiple contact interactions are required to drive the cells to adhesion readiness and to prevent developmental slip-back.
在纤毛原生动物嗜热四膜虫中研究了直接细胞接触与随后的细胞间黏附之间的关系。在有性生殖过程中，饥饿的互补交配型混合后约1小时开始成对黏附。然而，已知配对前细胞之间的直接接触是黏附准备状态发展所必需的。我们在此发现，初始接触相互作用对于促使细胞达到黏附准备状态是必要的，但并不充分。还需要二次相互作用。我们采用了两种不同的实验策略。首先，我们研究了一个突变体的影响，该突变体无法配对，但在与两种不同的野生型交配型细胞混合时能刺激它们配对。我们发现该突变体的刺激只是部分的；野生型细胞对突变体细胞的反应是停止形成食物泡，但没有经历顶端转化或伴刀豆球蛋白A（Con A）受体倾斜。此外，动力学分析表明，当部分受刺激的野生型细胞混合在一起时，配对形成略有延迟，这使得这些配对前的过程有时间发生。这表明，除了初始接触相互作用之外，受突变体刺激的野生型细胞还需要后续相互作用，而突变体无法实现这种相互作用。其次，我们发现，在野生型交配型细胞混合后的不同时间间隔阻断它们之间的接触相互作用，可以防止顶端转化和Con A受体倾斜进一步增加。此外，这两个过程都出现了逆转。这表明需要多次接触相互作用来促使细胞达到黏附准备状态并防止发育倒退。
