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http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/57482
標題: | 探討rab7 遺傳相關基因ifc 於果蠅中對神經脂質平衡、
膜狀胞器運送及細胞死亡機制影響 The role of rab7-interacting gene, infertile crescent (ifc), in sphingolipid metabolism, endolysosomal trafficking and cell death in Drosophila |
作者: | Wei-Hung Jung 榮偉宏 |
指導教授: | 詹智強(Chih-Chiang Chan) |
關鍵字: | 果蠅,神經脂質,膜狀胞器運輸,細胞死亡, Drosophila,ifc,rab7,sphingolipid,cell death, |
出版年 : | 2014 |
學位: | 碩士 |
摘要: | Rab7 GTPase 為真核細胞中endolysosomal trafficking 重要調控者。人類Rab7
點突變會導致顯性遺傳的週邊神經退化症Charcot-Marie-Tooth 2B(CMT2B)。但目前 對其致病機轉尚未了解,而果蠅在rab7 序列高度保守及遺傳工具的便利,為我們研 究rab7 重要之模式動物。rab7 基因剔除果蠅在蛹晚期即死亡,其外觀和野生型(wild type)無異,但在死前腦中會有內體(endosome)堆積情形,且以eyFlp 在成蟲眼睛建立 缺少rab7 細胞並給予光照刺激後,其視神經之突觸傳遞功能幾乎消失,表示失去 rab7 會導致神經漸進性的喪失功能。 為更瞭解 rab7 造成神經退化之機制,我們以視神經之突觸傳遞功能為基礎, 使用異型合子(heterozygous) rab7 剔除果蠅進行大規模遺傳篩選。發現一基因infertile crescent (ifc),不管是過度表現或是失去部分功能,都會惡化視神經突觸功能。ifc 乃 演化上高度保留之酵素,負責將dihydroceramide (DHC) 轉變成為神經醯胺(ceramide)。 而在ifc 失去功能下,果蠅會無法發育至成蟲並且有成蟲盤(imaginal discs)萎縮現象, 而在幼蟲時期,脂肪體(fat body)和眼盤(eye discs)則會有dihydroceramide 訊號堆積, 及內體(endosome)不正常分布情形。我們的研究除了確立rab7 及ifc 在果蠅神經系統 之中扮演的角色,也將intracellular membrane trafficking 和神經脂質(sphingolipid)之 平衡連結在一起,除對基因研究有貢獻外,或許也能藉改變神經脂質(sphingolipid)量 以達成治療神經退化疾病之願景。 The small GTPase Rab7 is a master regulator of endolysosomal traffickingin all eukaryotic cells.In drosophila, loss of rab7 leads to lethality at late pupal stage with no gross morphologicalabnormalities. Whole-mount brain preparations of the rab7 null mutant in early pupal stages reveal substantial accumulations of the endosomal marker Hrs, indicating a defect in endolysosomal trafficking. Photoreceptors of newly hatched rab7 mutant initially function without obvious defects, as indicated in electroretinogram (ERG) recordings. In contrast, 5 day-old null mutant or 14 day-old heterozygous mutant, both raised under constant light stimulation, exhibit significant loss of synaptic function. To discover the mechanism underlying rab7-dependent synaptic transmission defects, we perform a modifier screen for rab7-interacting genes in Drosophila. Among 477 candidates, infertile crescent (ifc) is identified as a candidate which enhances the rab7- dependent synaptic transmission defects.Throughout evolution, infertile crescent is a highly conserved enzyme converting dihydroceramide into ceramide. In our study, we find that loss of ifc cause atrophy of imaginal discs and affect morphology and function of adult eye. In the larval stage, there are dihydroceramide signals accumulation and endosome abnormal distribution in fat body and eye discs.Taken together, our study has identifiedthe interaction of rab7 and ifc in Drosophila, and connects the intracellular membrane trafficking to sphingolipid metabolism. These findings not only add to genetic studies of rab7 and ifc but, with new perspectives on altering sphingolipid levels, shed light on potential therapeutic targets toward neurodegenerative diseases. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/57482 |
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顯示於系所單位: | 生理學科所 |
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