中文摘要
Echinoid（Ed）是一個細胞粘著分子（CAM），具有七個immunoglobulin（Ig）domains, 兩個 fibronectinIII（FnIII）domains，一個transmembrane domain，及C端315個與已知的分子序列無結構或功能相似性的區域，除了其最末端四個胺基酸為一PDZ-binding motif.
Ed 已被發現具有多重功能，在果蠅複眼發育的過程中，它會抑制EGFR signalling，而在果蠅背板剛毛的分化過程中，它會促進 Notch signalling，此外Ed 也被發現會與DE-Cadherin 協同作用，進而控制細胞之間的固著。然而Ed進行這些功能的詳細分子機制尚未被完全了解。
要進一步闡明Ed的多重功能，必須要找到與Ed直接進行結合交互作用的目標分子。因此在本研究中，我們進行了酵母菌雜交篩選及GST-pulldown，以搜尋這些分子。在這些實驗中，我們找到了三個可能的蛋白質：CG6167，Par6，及Stardust（Sdt）。此三者皆具有至少一個的PDZ domain，而其中Par6及Sdt為兩個表皮細胞間隙分子群的分子，參與了表皮細胞極性的調控。
我們進行遺傳混合性同行合子分析，發現Par6在ed突變細胞群與正常細胞的介面有減少乃至於消失的現象。而大量表現Ed亦造成Par6的減少。反之，在par6或sdt突變的情況下，Ed的表現卻不受影響。我們推論，Ed可能易於結合具有PDZ domain的分子，並很可能藉由與Par6,Sdt結合而將它們送至正確的位置。

Abstract
Ecionoid（ED） is a cell-adhesion molecule(CAM) which is comprised of 7 immunoglobulin(Ig) domains, 2 fibronectin type III(FnIII) domains and a transmembrane domain, followed by intracellular 315 amino acids with no structural or functional motif except for the last 4 residues(EIIV) which is capable of binding PDZ domains.
Ed has been reported to have multiple functions. Previous studies have shown that Ed negatively regulates EGFR signaling during development of Drosophila compound eye, whereas facilitates Notch signaling in mesothoratic bristle development. In addition, ED was reported to be an essential component cooperating with DE-cadherin, a adherens junctions（AJ） molecules, to mediate cell-cell adhesion. However, the detailed mechanisms of how Ed works remain unclear.
To elucidate the mechanisms of ED’s diverse functions, it is essential to identify the molecules that directly interact with ED. We performed yeast two hybrid analysis and GST pulldown experiments in search of them. Three candidates were isolated: CG6167（by yeast two-hybrid screen）, Par6, and Stardust（by pulldown experiments）, each contains at least one PDZ domain. Par6 and stardust are two key determinants in regulating epithelial cell polarity.
Genetic mosaic analysis in wing imaginal discs showed that Par6 is missing at the interface between ed clones and wildtype cells. Ectopic expression of Ed causes downregulation of Par6.However, removal of either Par6 or Stardust seems to affect neither expression level nor distribution of ED. The overall polarity and integrity of epithelial cells are not affected. The results suggest that (1) ED has a bias to bind PDZ-containing proteins (2) ED may binds Par6 and Stardust and localizes them to Ajs.

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