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標題: | 線蟲神經系統粒線體型態在老化過程中的遺傳分析 Genetic Analysis of Age-Dependent Mitochondrial Fragmentation in C. elegans neurons |
作者: | Hao-Ching Jiang 姜浩菁 |
指導教授: | 潘俊良(Chun-Liang Pan) |
關鍵字: | 線蟲,神經老化,神經活性,粒線體,內質網與粒線體的聯繫, C. elegans,neuronal aging,neural activity,mitochondria,ER-mitochondrial contacts, |
出版年 : | 2014 |
學位: | 碩士 |
摘要: | 老化造成行為及認知上的衰退,並且伴隨著神經元結構以及功能的退化。Caenorhabditis elegans線蟲具有比哺乳動物相對較短的壽命並且是很好的基因體研究工具,我們實驗室利用線蟲作為實驗動物來研究神經老化的細胞分子機制。我們過去研究發現年老的線蟲觸覺神經會出現型態上的變化,而且也證明神經活性在老化的過程中對於維持正常神經元型態是很重要的。本篇研究發現觸覺神經裡被螢光標的的粒線體隨著老化逐漸變得破碎,因此粒線體型態的改變可以被視為神經老化的特徵。透過螢光蛋白標的,這些破碎的粒線體碎片廣泛地和溶小體重疊,暗示著神經老化促進粒線體自噬增加的可能性。內質網與粒線體之間的緊密聯繫對於脂質生合成、鈣離子平衡以及粒線體的動態平衡是重要的;但這兩個胞器之間的聯繫會在神經老化早期發生顯著的分離。hsf-1基因的突變會縮短線蟲的壽命,同時也會使粒線體的破碎提早發生;相反地,daf-2基因的突變會延長線蟲的壽命,並且會延緩粒線體發生碎裂。我們也證明了上皮鈉離子通道/退化蛋白 (epithelial sodium channel/degenerin, ENaC/Deg)的家族成員mec-4基因,以及電壓門控性鈣離子通道(voltage-gated calcium channel)的編碼基因egl-19對於維持觸覺神經裡粒線體型態的完整是重要的,因為在這兩種基因突變的情況下都會增加粒線體在老化過程發生碎裂的機率,而且它們是作用在同一條途徑來調控粒線體的型態。另外,在鈣離子/鈣調素依賴性蛋白激酶白激酶(CaMKII)的基因unc-43突變也看到粒線體在老化過程中提早發生碎裂的情形,類似其在mec-4和egl-19突變裡看到的表現,暗示unc-43作用在神經去極化的下游。然而,粒線體分裂蛋白基因drp-1被移除後可以抑制因為失去神經活性而造成的過度粒線體碎裂。在本篇研究中我們發現神經活性可以調控在老化過程中粒線體的型態。 Age-dependent behavioral and cognitive decline is accompanied by structural and functional deterioration in senescent neurons. Modeling neuronal aging in the mammalian brain is hampered by the relatively long life span of the common lab mammals. Robust genetics and the short life span make Caenorhabditis elegans a promising model to investigate the molecular and cell biological basis of neuronal aging. In our previous study, we found that characteristic age-dependent defects occur in the C. elegans touch neurons, and sensory evoked activity is required to maintain neuronal integrity during aging. Here we report that progressive mitochondrial fragmentation is a hallmark of touch neuron aging, and that sensory evoked activity is required for a balanced mitochondrial dynamics in these neurons. Our FRAP analysis suggested that mitochondrial fragmentation documented with fluorescent probes did indicate physical disconnection of this organelle. Small mitochondrial fragments colocalized extensively with lysosomes, suggestive of age-dependent mitophagy in these neurons. Moreover, endoplasmic reticulum-mitochondria contact, which is critical for lipid synthesis, calcium homeostasis and mitochondrial dynamics, was lost early during aging. Mutations in hsf-1, which shorten C. elegans life span, markedly accelerated mitochondrial fragmentation in the touch neurons. A daf-2 mutation dramatically extended life span and also delayed mitochondrial fragmentation. Similar to axonal integrity in senescent touch neurons, maintenance of mitochondrial dynamics required sensory evoked activity. We showed that mutations in mec-4 and egl-19, which encode a Degenerin family sodium channel and a voltage-gated calcium channel, respectively, induced premature onset of mitochondrial fragmentation in the touch neurons, and the two genes acted in a common pathway. Mutations in the CaMKII gene unc-43 caused similar phenotypes, suggesting that CaMKII regulates mitochondrial morphology downstream of neuronal depolarization. Mitochondrial defects in neurons losing membrane activation could be suppressed by mutations in drp-1, which is a dynamin-related GTPase critical for mitochondrial fission. Togther this work uncovers mechanism by which neuronal activity regulates mitochondrial dynamics in aging touch neurons. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/55942 |
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顯示於系所單位: | 分子醫學研究所 |
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