Cell sorting is a morphogenetic processthat cell populations with different identities may segregate from each other. Being a major cellular adhesion molecule on adherens junction, Drosophila epithelial cadherin (DE-cadherin), the homologue of E-cadherin in Drosophila, can mediate cell-cell adhesion through the extracellular domain that interacts with other cadherins and through the intracellular domain that forms the cadherin-catenin complex. Alterations in DE-cadherin expression levels may lead to cell sorting by changing the adhesivity. On the purpose to investigate how cadherins mediate cell sorting, I overexpressed cadherins, the truncated forms and the chimera cadherins under the control of GAL4-UAS system in Drosophila wing discs and subsequently observed the phenotypes in a macro view. The results in this study revealed that a full-length of cadherin was required for the mediation of cell sorting behavior. Both the extracellular domain and the intracellular domain of a cadherin were required, however, not sufficient while acted alone, for cell sorting. Signals from cell-cell contact had to transmit to the cytoskeleton through interactions of the cadherin-catenin complex, cooperatively, to mediate the cell sorting behavior of cell populations.

細胞分離（cell sorting）是一種形態生成的過程當中常見的現象：性質不相同的細胞會傾向與彼此分離；而使得性質接近或相同的細胞聚集在一起。果蠅的上皮鈣黏著分子（Drosophila epithelial cadherin, DE-cadherin）是細胞黏著分子（cellular adhesion molecule）的一種，可以透過其細胞外的結構與其他上皮鈣黏著分子進行順式或反式的結合，並同時藉由其細胞內結構與連環蛋白（catenin）形成複合物，以調控細胞與細胞之間的連結。改變上皮鈣黏著分子的表現量會影響細胞間的黏著作用，因而導致了細胞分離現象的產生。為了瞭解上皮鈣黏著分子是如何調控細胞分離的現象，在這個研究當中我利用了GAL4-UAS system將全長、截短以及嵌合等形態的鈣黏著分子大量表現在果蠅的翅碟（wing disc）上，並且以巨觀的角度探討鈣黏著分子對於細胞分離現象的調控。實驗結果顯示，只有全長的鈣黏著分子得以調控細胞分離的現象。單就細胞外結構或是細胞內結構的表現量改變是不足以使細胞群分離開來的，兩者必須共同作用，使得細胞與細胞接觸時的訊息藉由鈣黏著分子與連環蛋白所形成的複合物進一步地傳遞至細胞骨架（cytoskeleton），以調控細胞分離的行為與現象。

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