於動物體發育的過程中，細胞間的黏著在組織修補、組織再生及細胞型態發生(morphogenesis)上扮演決定性的角色。細胞間不同的黏著作用可以促進相同細胞群體間的辨識與聚合，甚至促使不同細胞群體分離且形成明顯相隔的聚落。在果蠅的wing imaginal discs上，數種不同的分子可共同調控在adherens junctions (AJs) 中的細胞黏著作用。Echinoid (Ed) 是一個具有免疫球蛋白區域 (immunoglobulin domain)的細胞黏著分子，一般存在於AJs上。Drosophlia E-cadherin (DE-cad) 則是在AJs裡最主要的細胞黏著分子，DE-cad可與Ed共同合作以調控細胞間的黏著。而身為Ed的paralogue，另一個分子Friend of echinoid (Fred) 也被預期可以調控細胞之間的黏著。於本研究中，我們結合了數種RNAi及異位表現 (ectopic expression) 技術以幫助我們理解Ed、Fred及DE-cad之間的關係。當我們在ed-RNAi clone裡大量表現Fred蛋白，不僅細胞群體的同性相聚作用 (cell sorting) 會被破壞，細胞甚至表現出分散 (scattering) 的新性狀。clone細胞中的DE-cad被動地減少，而Ed、Fred及DE-cad的分佈差異最後促使細胞彼此分離。經由本研究推論即使Fred蛋白與Ed蛋白結構十分相似，Fred蛋白卻提供了與Ed不相同的黏著功能。

During animal development, cell adhesion plays a critical role in tissue repair, regeneration and morphogenesis. Different adhesive interactions between cells promote the recognition and assembly of cells with similar properties and also lead them to segregate into distinct cell populations. In Drosophila wing imaginal discs, several components involve in the regulation of cell adhesion at adherens junctions (AJs). Echinoid (Ed) is an immunoglobulin domain-containing cell adhesion molecule (CAM) that localizes to AJs. Drosophila E-Cadherin (DE-cad), the major CAM of AJs, cooperates with Ed to mediate adhesion in wing discs. And another CAM called Friend of echinoid (Fred), which is a paralogue of Ed, is also predicted to provide some efforts in regulating adhesion in AJs. In this study, we combine several RNAi and overexpression experiments to comprehend the relations between Ed, Fred and DE-cad. Overexpression of Fred in ed RNAi clones can not only rescue the sorting phenotype but further trigger the clone cells to scatter. During this process, DE-cad decreases passively at the contact sites, and the differential distributions of Ed, Fred and DE-cad between clone and wild-type cells finally induce the scattering phenotype. Our study reveals that, although sharing high similarity with Ed, the adhesive function of Fred is different from Ed.

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