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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75215
標題: | 一個新的Dpp訊息路徑成員,dSMIF,在卵發育時期為母源軸向決定因數的定位所需 dSMIF, a novel component in Dpp signaling pathway, is required for maintaining the localization of maternal axial determinants in Drosophila oogenesis |
作者: | 範世榮 |
出版年 : | 2001 |
學位: | 碩士 |
摘要: | 果蠅胚胎的前後軸向的形成,在卵發生時期就已決定。在卵發育中期,bcd與osk mRNA的不對稱的分佈提供了一個主要的機制,其中osk mRNA在卵中的坐落位置決定未來胚胎腹部與生殖前驅細胞的形成。當參與osk mRNA定位的基因發生突變時,會使得胚胎腹部與生殖前驅細胞無法正確的形成,造成胚胎腹部腹節缺失的posterior group突變性狀。 Smad是TGF β訊息路徑中不同的Smad蛋白質所共用的轉錄因數。人類的SIF, Smad Interacting Factor,與Smad有蛋白質-蛋白質間的結合。果蠅的Smad 結合蛋白,dSIF,在生殖細胞進行的基因重組分析搜尋中,因為呈現腹部腹節缺失的posterior group突變胚胎性狀而被篩選研究。dSIF與人類SIF在N端形成演化上相當保守的區域。在dSIF突變缺失的基因背景下,卵殼呈現腹部化現象,這與Dpp(Decapentaplegic,果蠅的TGF β同源基因蛋白)的受體基因突變時腹部化的卵殼性狀相吻合;由於dSIF突變可以抑制因為Dpp過度表現所呈現的胚胎背部化的性狀,這顯示dSIF與Dpp路徑有相互作用的關係。 在dSIF突變的卵巢中,osk mRNA及Osk蛋白的表現量皆呈現下降或消失的性狀,但在定位上卻是正常的;Staufen (Stuf)和Gurken(Grk,果蠅的TGFα)蛋白質的表現量亦呈現下降或消失的性狀。這些現象與Dpp受體基因突變時,會產生母源產物無法運送到卵細胞的性狀相類似。因此,在dSIF突變中母源產物的普遍性而非專一性的減少及dSIF蛋白於護理細胞與卵細胞交接處如守門員似的分佈加上其分子上的特性,我們推測dSIF很可能參與運送母源產物的機制。 Body axis of Drosophila embryos is determined through the asymmetry localization of maternal components during oogenesis. In the mid-oogenesis, two key components, bicoid (bcd) mRNA and oskar (osk) mRNA, distribute anteriorly and posteriorly of the oocyte, respectively. Mutations of genes resulted in osk mRNA mislocalization produce the posterior group embryonic phenotype, which was previously defined as the lost of abdomen and pole cells. Smad is the common mediator of TGFβ signaling pathway. In human, the binding between SIF (Smad interacting factor) and Smad implicate the possible function of SIF in TGFβ signaling. In this study, the Drosophila homologue of SIF, dSIF, is identified because of its maternal-effect posterior group defect. The eggs derived from dSIF mutant female exhibit ventralized eggshell phenotype similar to that are laid by mother carrying decapentaplegic (dpp, Drosophila TGFβ homologue) receptor mutant. Furthermore, dorsalized embryonic phenotype caused by dpp and thick vein (tkv) overexpression could be suppressed by dSIF mutant. It is suggested that dSIF is a new component acting in Dpp signaling. During oogenesis, dSIF is essential for the formation of the proper level of Osk protein and mRNA; nevertheless, their localizations are not affected in mutant. The expression level of Staufen (Stau) and Gurken (Grk) also decreased. In dpp receptor mutants, saxophone (sax) and tkv, their mutant ovaries exhibited maternal-component transport defect phenotype. Based on the general but not specific decrease of maternal components and the nearby oocyte-nurse cell-junction gatekeeper-like localization of dSIF protein in egg chamber, we propose that dSIF may participate in the transportation mechanism of maternal components from nurse cells to oocyte. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75215 |
全文授權: | 未授權 |
顯示於系所單位: | 動物學研究所 |
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