Echinoid (Ed) 是一個具有免疫球蛋白區域 (immunoglobulin domain) 的細胞黏著分子。它在眼睛發育過程中負調控 EGFR 訊息，也可和 Notch 信號合作影響感覺性剛毛的發育。此外，Ed 是 adherens junctions (AJ) 的一員，可和DE-cadherin 共同調控細胞的黏著性。為了要尋找與 Ed 細胞內部區域產生作用的下游分子，我們曾利用果蠅胚胎萃取物進行親合性色譜分析，並運用質譜技術鑑定蛋白質身份。其中一個被沉澱下來的蛋白為果蠅 serine-threonine kinase receptor-associated protein 的同源分子 (D-STRAP)。雖然 Ed 能與 D-STRAP 相互作用，但 STRAP 在哺乳動物的細胞培養實驗中被證實參與在 transforming growth factor-β (TGF-ß) 訊息當中。
為了要了解 D-STRAP 發育上的功能，我們在果蠅的 eye imaginal discs 上製造了含有 D-STRAP 突變的細胞，並發現如此情況下會造成突變細胞表皮的收縮而促使果蠅小眼排列不規則。同時我們也觀察到突變感光神經的細胞核具有往基部視柄移位的現象；然而突變細胞的分化並沒有受到影響。為了進一步了解 D-STRAP 是否參與在 TGF-ß 信號當中，我們以 Mothers against decapentapelagic (pMad) 作為激發 TGF-ß 信號的根據，並觀察它在眼睛發育上的表現。然而，相較於含有 thick veins (tkv) 突變的情形下，我們並沒有在D-STRAP 突變的細胞內觀察到 pMad 表現的消失。於是我們推論 D-STRAP 可能不是參與在 TGF-ß 信號當中。

Echinoid (Ed) is an immunoglobulin domain-containing cell adhesion molecule (CAM). Ed negatively regulates epidermal growth factor (EGF) receptor signaling pathway during eye development and cooperates with Notch pathway during sensory bristle development. Moreover, Ed is a component of adherens junctions (AJ) that cooperates with DE-cadherin to mediate cell adhesion. To identify novel molecules associated with the intracellular domain of Ed, affinity chromatography of embryonic lysate followed by the protein identification with matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry has been conducted. One major co-precipitated protein was identified to be the Drosophila homologue of serine-threonine kinase receptor-associated protein (D-STRAP). Although Ed associates with D-STRAP, however it was shown that STRAP is involved in the transforming growth factor-β (TGF-ß) signaling in mammalian cell cultures.
To determine the function of D-STRAP during development, we generated homozygous D-STRAP mutant clones in eye imaginal discs. We observed apical constriction in D-STRAP clones that in turn causes the ommatidial disorganization and mislocalization of photoreceptor nuclei toward the basally localized optic stalk. However, the specification of mutant photoreceptor neurons is not affected. To determine whether D-STRAP is involved in the TGF-ß pathway, we examined the expression of phosphorylated form of Mothers against decapentapelagic (pMad), a reporter of TGF-ß activation during furrow progression. In contrast to thick veins (tkv) clones, we failed to detect the loss of pMad staining in D-STRAP clones. Together, we conclude that D-STRAP may not involved in the TGF-ß signaling pathway.

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