果蠅Processing body成員,dGe-1參與卵母細胞的細胞骨架組成

Abstract

在果蠅卵子發育(oogenesis)時期，母源訊息核醣核酸(maternal mRNA)， 如oskar mRNA，坐落在卵母細胞(oocyte)的後端並決定胚胎發育的軸向(axial determination)以及極細胞(pole cell)的發育。細胞內的微管(microtubule) 和纖維性機動蛋白(F-actin) 參與oskar mRNA的運送及卵子後端(posterior pole)的定位。 本論文研究人類促進去頭蓋大分子在果蠅中的同源基因 Drosophila Human enhancer of decapping large subunit (dHedls), 又稱為dGe-1(Gougerot syndrome)。 dGe-1在生殖細胞的缺失(dGe-1 loss-of-function in germline)，會影響卵母細胞內微管 A-P gradient和bundles的形成；同時也會使後期的細胞質流(ooplasmic streaming)有停滯的現象。 dGe-1突變的背景下，組成微管結構的單體微管蛋白(α-tubulin)和果蠅去頭蓋蛋白質2,dDcp2的表現量都會下降；且在此背景下，大量表現dDcp2可以抑制dGe-1缺失所造成的卵母細胞內微管失序的性狀；我們推論dGe-1和 dDcp2在微管調控上有複合體的關係。 經酵母菌雙雜交系統(yeast-two hybrid system)也證實 dGe-1和dDcp2彼此之間有直接的交互作用(physical interaction)。免疫螢光染色也觀察到dDcp2和dGe-1坐落在果蠅卵母細胞皮層處(oocyte cortex)，並有局部疊合(partial coloclaized)的現象。 因此我們推論dGe-1和dDcp2彼此之間會在卵母細胞皮層處有直接的交互作用，也共同調控細胞微管的組成， oskar mRNA在卵母細胞的運送及後端定位進而被影響。

In Drosophila oogenesis, the localization of the maternal mRNAs at specific positions, such as oskar mRNA, is an important mechanism, which regulates axial determination and pole cell development in embryogenesis. In Drosophila oocyte, the location and anchoring of oskar mRNA at posterior pole are regulated by F-actin and microtubules.First, in my study, the Drosophila Human enhancer of decapping large subunit, (dHedls), which also called dGe-1(Gougerot syndrome) mutant GLC displays microtubule disrupted phenotypes, which are A-P gradient lost in stage 9 oocytes and microtubules bundles lost in stage 10. Ooplasmic streaming is also obstructed. α-tubulin and Drosophila decapping protein 2 (dDcp2) protein expression levels decreased in dGe-1 homozygous mutant larvae. Besides, overexpress dDcp2 in germline cells can complement microtubule disrupted phenotype in dGe-1 mutant GLC. This indicates that dGe-1 and dDcp2 have synergy effect on microtubule regulation. In addition, there is a physical interaction between dGe-1 C-terminal and dDcp2 C-terminal, which has been proven by yeast-two hybrid analysis in my study. Further, in immunofluorescence staining, dGe-1and dDcp2 are partial colocalized at oocyte cortex. In conclusion, we proposed that the physical interaction of dGe-1 and dDcp2 in oocyte is to regulate microtubule organization, which is responsible for oskar mRNA localizing and anchoring at posterior pole of oocyte