臺灣博碩士論文加值系統

果蠅眼睛發育過程中，眼睛形成基因eyeless、twin of eyeless、 optix、eye gone、 sine oculis、eyes absent 及 dachshund 決定眼睛原質的命運，給予組織形成眼圓盤的潛能。眼圓盤形成之後，原神經基因atonal (ato) 及 daughterless (da)產生basic helix-loop-helix蛋白，並形成 heterdimers而促使細胞分化為感光細胞。眼圓盤的形態溝中，細胞會開始分化，同時表達Ato及較高量的Da。有趣的是：eyeless、twin of eyeless及optix 會在形態溝中、後被抑制到完全不表現。sine oculis 及eyes absent則在形態溝的前、後大量表現，但在形態溝則不表現。dachshund (dac) 則在形態溝前大量表現，而在後面只維持幾排細胞的低量表現。當異位表達eyeless (ey) 或同時異位表達eyes absent與 sine oculis在形態溝中時，造成Ato 表現被抑制及接下來的感光細胞分化失敗。由這些結果推論得知，眼睛形成基因在形態溝中的負調控，對於果蠅複眼的細胞分化是非常重要的。我發現在形態溝中 ato或 da 的突變組織中， Dac 與Ey的表現量會增加。同時異位表現Ato與Da在形態溝前，會造成Dac和Ey 在形態溝前的表現被抑制。當單獨表達Da時，也會造成類似，但較不有效的抑制效果。由原位雜合實驗得知， dac及 ey的負調控至少部份發生在轉譯階段，而對於其他眼睛形成基因，Ato與Da也可在轉譯階段抑制其表現。Da與VP16 的活化區域所建構的融合蛋白，能持續的促進果蠅背甲上感覺剛毛的發育。因此，DaVP16確實是一個活化形式的Da蛋白。而此融合蛋白在眼圓盤中，對Da的表現仍造成類似的抑制性效果。因此，Ato及Da功能上應為一個活化子活化一個抑制子進而抑制眼睛形成基因的表現。其他實驗結果也將在論文中一一討論。

In the Drosophila eye development, eye formation genes eyeless, twin of eyeless, optix, eye gone, sine oculis, eyes absent, and dachshund specify the eye primordium, giving it the potential to form an eye disc. After eye disc formation, the proneural genes atonal (ato) and daughterless (da) encode subunits of heterodimeric basic helix-loop-helix proteins that promote the differentiation of photoreceptors. In the morphogenetic furrow (MF), where photoreceptor differentiation initiates, cells express Ato and higher levels of Da. Interestingly, eyeless, twin of eyeless and optix are downregulated in the MF. sine oculis and eyes absent are highly expressed both anterior and posterior to, but not in, the MF. Expression of dachshund (dac) is at a high level anterior to the MF and repressed to a basal level in the MF. I shown that misexpression of eyeless, or combination of eyes absent and sine oculis across the MF causes Ato repression in the MF, and consequently failure of photoreceptor differentiation in the eye disc. These results suggest that negative regulation of eye formation genes in the MF is necessary for cell differentiation in the compound eye. I observed that expression of Dac and Eyeless is upregulated in da or ato mutant clones in the MF. Co-misexpression of Da and Ato causes Dac and Eyeless being downregulated anterior to the MF, and misexpression of Da alone also causes a similar, but less effective, downregulation. The negative regulation of dac and ey is at least partly at the transcriptional level, which is also observed for other eye formation genes. The fusion protein of Da and VP16 activation domain that functions constitutively to promote sensory bristle development, also causes similar repressive effect on Dac. Therefore, Ato and Da may function as an activator to activate a repressor of the eye formation genes. Several other results will also be presented in this thesis.

Abstract 1
中文摘要 2 Introduction 3 Materials and Methods 6 Results 13 Discussion 23 References 28 Figures 32 Appendix 41

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